Endangered and Threatened Wildlife and Plants; Endangered Species Status for Echinomastus erectocentrus var. acunensis (Acuña Cactus) and Pediocactus peeblesianus var. fickeiseniae (Fickeisen Plains Cactus) Throughout Their Ranges

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R2-ES-2012-0061; 4500030113]

RIN 1018-AY51

Endangered and Threatened Wildlife and Plants; Endangered Species Status for Echinomastus erectocentrus var. acunensis (Acuña Cactus) and Pediocactus peeblesianus var. fickeiseniae (Fickeisen Plains Cactus) Throughout Their Ranges

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Final rule.

SUMMARY:

We, the U.S. Fish and Wildlife Service (Service), determine that

Echinomastus erectocentrus

var.

acunensis

(acuña cactus) and

Pediocactus peeblesianus

var.

fickeiseniae

(Fickeisen plains cactus) meet the definition of endangered species under the Endangered Species Act of 1973, as amended. This final rule implements the Federal protections provided by the Act for these species. The effect of this regulation will be to add these species to the List of Endangered and Threatened Wildlife and Plants under the Endangered Species Act.

DATES:

This rule becomes effective October 31, 2013.

ADDRESSES:

This final rule is available on the Internet at

http://www.regulations.gov,

Docket No. FWS-R2-ES-2012-0061. Comments and materials we received, as well as supporting documentation used in the preparation of this final rule, are available for public inspection at

http://www.regulations.gov.

All of the comments, materials, and documentation that we considered in this rulemaking are available by appointment, during normal business hours at: U.S. Fish and Wildlife Service, Arizona Ecological Services Office, 2321 West Royal Palm Rd., Suite 103, Phoenix, AZ 85021; by telephone 602-242-0210; or by facsimile 602-242-2513.

FOR FURTHER INFORMATION CONTACT:

Steve Spangle, Field Supervisor, U.S. Fish and Wildlife Service, Arizona Ecological Services Field Office, 2321 W. Royal Palm Road, Suite 103, Phoenix, AZ 85021; by telephone (602) 242-0210; or by facsimile (602) 242-2513. Persons who use a telecommunications device for the deaf (TDD) may call the Federal Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Executive Summary

This document consists of a final rule to list as endangered

Echinomastus erectocentrus

var.

acunensis

(acuña cactus) and

Pediocactus peeblesianus

var.

fickeiseniae

(Fickeisen plains cactus) under the Act. For the remainder of this document, these species will be referred to by their common names.

Why we need to publish a rule.

On October 3, 2012 (77 FR 60509), we published proposed rules to list acuña cactus and Fickeisen plains cactus as endangered species and to designate critical habitat for both species. In this document, we finalize our determinations as endangered species for these species under the Act. The Act requires that a final rule be published within one year of a proposed rule in order to add species to the lists of endangered and threatened plants to provide protections under the Act. We have determined that critical habitat for the acuña cactus and the Fickeisen plains cactus is prudent and determinable in the proposed rule and will soon publish in the

Federal Register

our final determination designating critical habitat for both cacti. The final critical habitat designation and supporting documents will publish under Docket No. FWS-R2-ES-2013-0025, and can also be found at the above locations.

The Endangered Species Act provides basis for our action.

Under the Endangered Species Act, we can determine that a species is an endangered or threatened species based on any of five factors: (A) The present or threatened destruction, modification, or curtailment of its habitat or range; (B) Overutilization for commercial, recreational, scientific, or educational purposes; (C) Disease or predation; (D) The inadequacy of existing regulatory mechanisms; or (E) Other natural or manmade factors affecting its continued existence.

For the acuña cactus, the threats to the species and its habitat result from the effects of drought and climate change (Factor A) in combination with predation by native insect and small mammal predators (Factor C). Threats also result from habitat destruction, modification, and degradation from United States-Mexico border activities (Factor A) and nonnative, invasive plant species issues (Factor A). In addition, the existing regulatory mechanisms in place do not directly address the threats to the species.

For the Fickeisen plains cactus, the threats to the species and its habitat result from habitat destruction, modification, and degradation from livestock grazing (Factor A) in combination with predation by small mammals (Factor C) and natural environmental variability and the effects of climate such as drought. When combined with the above mentioned threats, small population size (Factor E) likely exacerbates the effects of these threats on the Fickeisen plains cactus. In addition, the existing regulatory mechanisms are not ameliorating threats to the species.

Peer review and public comment.

We sought comments from independent specialists to ensure that our designation is based on scientifically sound data, assumptions, and analyses. We invited these peer reviewers to comment on our listing proposal. We obtained peer reviews from two knowledgeable individuals for the acuña cactus and two knowledgeable individuals for the Fickeisen plains cactus, all with scientific expertise to review our technical assumptions, analysis, and whether or not we had used the best available information for both plants. These peer reviewers generally concurred with our methods and conclusions and provided additional information, clarifications, and suggestions to improve this final rule. Information we received from peer review is incorporated in this final revised designation. We also considered all comments and information received during the comment period.

Organization of Document

The layout of this rule is as follows: the final listing determination of the acuña cactus and the final listing determination for the Fickeisen plains cactus.

Previous Federal Actions

Please refer to the proposed listing rule for the acuña cactus and Fickeisen plains cactus (77 FR 60509; October 3, 2012) for a detailed description of previous Federal actions concerning these species.

Summary of Changes From Proposed Rule

Since the publication of the October 3, 2012 (77 FR 60509), proposed rule to list and designate critical habitat for the acuña cactus and Fickeisen plains cactus, we have made the following changes in this final rule:

(1) Based on information received from public comments, we reevaluated the threat of nonnative, invasive plants on the acuña cactus. As a result, we

determined that nonnative, invasive plants currently occur in the vicinity of several populations of acuña cactus, including the largest known population, and will become a threat to the acuña cactus in the near future. Therefore, we conclude nonnative, invasive species pose a threat to the acuña cactus and its habitat.

(2) Based on information received from public comments that both affirmed and refuted the threat of nonnative, invasive plants on the Fickeisen plains cactus, we reevaluated this threat. We conducted a thorough review of available information and reassessed the distribution of nonnative, invasive species to Fickeisen plains cactus populations, including their risk of exposure and potential population-level outcomes. We conclude that nonnative, invasive species are stressors on the landscape within the range of the Fickeisen plains cactus, but at this time, we lack site-specific information on which species are present; their abundance, density, and distribution relative to Fickeisen plains cactus populations; and evidence that the cactus is negatively affected by nonnative invasive plants. Therefore, we conclude that there is insufficient evidence that nonnative, invasive species are a threat to the Fickeisen plains cactus at this time.

(3) We have added a discussion concerning the occupancy of the Fickeisen plains cactus on the Kaibab National Forest at South Canyon in House Rock Valley. The South Canyon population is now the only known Fickeisen plains cactus occurrence on National Forest Service Lands. Please see

Abundance and Trends

for more information.

(4) Based on questions raised from a public comment, we reviewed our discussion of

Factor D: Inadequacy of Existing Regulatory Mechanisms.

We acknowledged in the October 3, 2012, proposed rule that there were adequate existing regulatory mechanisms in place for the Fickeisen plains cactus, as mechanisms appear to provide adequate protection to the cacti and its habitat in the manner they were intended to provide. We have furthered this conclusion by noting that the existing regulatory mechanisms in place do not ameliorate the threats to the Fickeisen plains cactus.

Summary of Comments and Recommendations

We requested written comments from the public on the proposed listing and designation of critical habitat for the acuña cactus and the Fickeisen plains cactus during two comment periods. The first comment period, associated with the publication of the proposed rule (77 FR 60509), opened on October 3, 2012, and closed on December 3, 2012. We requested written comments on the proposed listing and critical habitat rule and the associated draft economic analyses during a comment period that opened on March 28, 2013, and closed on April 29, 2013, (78 FR 18938). We contacted all appropriate Federal, State, tribal, and local agencies; scientific organizations; and other interested parties and invited them to comment. Newspaper notices concerning the proposed rule and inviting the general public to comment were published by two local newspapers. We did not receive any requests for a public hearing, and thus, none were held.

During the comment periods for the proposed rule, we received 16 comment letters, including four from peer reviewers, directly addressing the proposed listing of the acuña cactus and the Fickeisen plains cactus with endangered status. All substantive information provided during the comment periods has either been incorporated directly into this final determination or addressed below.

Peer Review

In accordance with our peer review policy published on July 1, 1994 (59 FR 34270), we solicited expert opinion from three knowledgeable individuals on the acuña cactus and six on the Fickeisen plains cactus having scientific expertise that included familiarity with the respected taxon and its habitat, biological needs, and threats. We received responses from two of the peer reviewers for the acuña cactus and two for the Fickeisen plains cactus.

We reviewed all comments received from the peer reviewers for substantive issues and new information regarding the listing of the acuña cactus and the Fickeisen plains cactus. The peer reviewers generally concurred with our methods and conclusions and provided additional information, clarifications, and suggestions to improve the final rule. Peer reviewer comments are addressed in the following summary and incorporated into the final rule as appropriate.

Peer Reviewer Comments

(1)

Comment:

Two peer reviewers commented that Flora of North America, Volume 4 (2003) presents a more recent taxonomic treatment of

Pediocactus

species than Benson (1982). It recognizes nine species of plants in the genera

Pediocactus,

not seven as stated in the proposed rule. Additionally, one peer reviewer commented that Flora of North America considers the Fickeisen plains cactus a subspecies of

Pediocactus peeblesianus.

The peer reviewer pointed out that we stated that the variety

fickeiseniae

was never validly published; therefore, we should use the current taxonomy.

Our Response:

We have corrected our statement in the rule (see

“

Taxonomy” under “

Species Description

”) that there are nine recognized species of

Pediocactus

in the United States, eight of which are endemic to the Colorado Plateau. We have referred to the Fickeisen plains cactus (

Pediocactus peeblesianus

var.

fickeiseniae

) as a variety since it was categorized as a candidate species in 1980 based on Benson (1969) and Heil

et al.

(1981). In regard to the current taxonomic treatment of the Fickeisen plains cactus, we are aware that Flora of North America considers the cactus a subspecies of

Pediocactus peeblesianus.

Other taxonomic organizations (e.g., Integrated Taxonomic Information System), however, treat the cactus as a variety and continue to use the name

Pediocactus peeblesianus

var.

fickeiseniae.

We recognize that revising the taxonomy of the cactus should be addressed. In the future, we will inquire into the reasons these organizations differentiate the cactus as a subspecies versus a variety for species management. Under the Act and in regard to plants, we treat variety and subspecies equally (43 FR 17912) in that we do not differentiate between a variety and subspecies when assigning priority classifications to species for listing, delisting, reclassification, or recovery actions (43 FR 43103). We continue to treat the Fickeisen plains cactus as a variety until there is broad acceptance among the botanical community that the cactus should be recognized as subspecies

fickeiseniae.

(2)

Comment:

One peer reviewer requested a discussion in the final listing rule about the possibility of hybridization between

Pediocactus

species whose ranges converge or overlap with the Fickeisen plains cactus on the Arizona Strip.

Our Response:

Three other species of

Pediocactus

occur near the Fickeisen plains cactus:

Pediocactus sileri

(Siler's pincushion cactus),

Pediocactus paradinei

(Kaibab plains cactus), and

Pediocactus bradyi

(Brady pincushion cactus). Phillips

et al.

(1982, p. 8) considered the possibility of hybridization from two nearby

Pediocactus

species in their status report for the Fickeisen plains cactus but did not find evidence of hybridization occurring. Porter (2002,

unpublished report) conducted DNA sequencing between

Pediocactus

species to investigate phylogenic relationships. Although he did not necessarily investigate hybridization among the species, his study would have illuminated any potential hybridization in that evolutionary lineages would be unclear. In our review of the Fickeisen plains cactus, we did not receive information of a discovery of a population having a high degree of variation among individuals that are similar in character to the Fickeisen plains cactus and another

Pediocactus

species. While the potential for hybridization exists, we are not aware of this possibility being apparent.

(3)

Comment:

Two peer reviewers suggested further discussion of the damaged Fickeisen plains cactus with orange-red material observed on the Navajo Nation, and which may be an infestation of the cactus borer beetle (

Moneilema semipuctatum

). One reviewer stated that larva from this beetle have been documented in

Pediocactus despainii

as well as

Sclerocactus wrightiae

in Capitol Reef National Park where the mortality of

Sclerocactus

plants have increased following drought years. The other reviewer stated that the cactus borer beetle impacts can be difficult to detect and are often misidentified as drought mortalities.

Our Response:

We have added a discussion of the cactus borer beetle under

Factor C: Disease and Predation.

Based on the information provided by the peer reviewer, infestation by the cactus borer beetle on other cacti species has resulted in mortality. Other than information presented by the Navajo Nation in 1994 of suspected damage to a Fickeisen plains cactus by a cactus borer beetle, we are not aware of any other individuals being affected. As stated in the proposed rule, the Navajo Nation noted no insect or disease reported for the Salt Trail Canyon population in their 2006-2008 report.

(4)

Comment:

One peer reviewer commented that cheatgrass (

Bromus tectorum

) is ubiquitous throughout the American West, noting that, while densities vary from year to year depending on rainfall, the plant has been documented on substrates on which the Fickeisen plains cacti grow and has been identified as a future problem in close proximity to the habitat of this cactus. The reviewer further added that any annual invasive species would have similar impacts of competition with respect to Fickeisen plains cactus seedling germination and establishment and requested further discussion of the impacts of invasive annual species.

Our Response:

The impact of nonnative species on the Fickeisen plains cactus and its habitat is unclear. Several species of exotics occur across its range with cheatgrass being the most widespread followed by red brome and redstem filaree. The past and present Navajo Nation botanists have opposing views on the effect of exotics. The current position of the Navajo Nation is that more research is required to fully understand if a negative relationship exists between exotic species and the cactus, and if abundance of exotics is contributing to declines in cactus numbers or preventing the successful germination and establishment of seedlings. We acknowledge that densities of cheatgrass may vary depending on rainfall: In years of above-average precipitation, cheatgrass densities may be high creating a fine fuel source that could increase the fire risk and fire frequency of an area. Following a fire, cheatgrass can quickly spread across the landscape and become a dominant species effectively promoting recurrent fires in the future. However, habitat across the range of the Fickeisen plains cactus is not contiguous in that plants occur in more grassland habitat in Mohave County then in Coconino County where vegetation is sparser. We agree with the peer reviewer that invasive species would increase the risk of fire to native plants and can directly and indirectly compete for soil moisture, nutrients, space, and light. At this time, we do not have sufficient information to determine the distribution of exotic annual species in relation to Fickeisen plains cactus habitat. We also lack information describing direct and indirect effects exotics that have on the plant and its habitat.

(5)

Comment:

One peer reviewer questioned why we stated we did not have sufficient information to evaluate whether the presence of nonnative, invasive species would facilitate the spread of wildfire into the habitat of the Fickeisen plains cactus.

Our Response:

Most of the habitat of the Fickeisen plains cactus in Coconino County consists of open areas with sparse vegetation and gravelly soil. The habitat in Mohave County that supports the Fickeisen plains cactus occurs in dense grass where there may be a potential fire risk from exotic annual grasses. As we previously stated, densities of cheatgrass vary across the range of the Fickeisen plains cactus, in addition to densities of other nonnative, invasive species or noxious weeds. If already existing within Fickeisen plains cactus habitat, densities of the nonnative, invasive species may increase in response to rainfall amounts and frequencies, thereby competing with the cactus for soil moisture, nutrients, space, and light. The nonnative, invasive species may also create fuels during the dry summer months and make the habitat prone to a wildfire. Given the diminutive size of the Fickeisen plains cactus, it would likely be killed by a wildfire. With sufficient information to support that high densities of exotics occur in Fickeisen plains cactus habitat, we would consider fire a significant threat. No evidence, however, leads us to believe that densities of cheatgrass or other exotic annual species near Fickeisen plains cactus habitat present a significant threat. No new information concerning the effects of fire and invasive species on the taxon was provided to us during the comment periods.

(6)

Comment:

One peer reviewer expressed concern about the level of protection afforded the Fickeisen plains cactus from the Northern Arizona 20-year Mineral Withdrawal (Public Land Order Number (PLO) 7787) on public lands in the vicinity of Grand Canyon National Park. The peer reviewer noted that not all populations would be protected based on their location near canyon rims and the entire habitat has not been surveyed. The peer reviewer also questioned the finality of PLO 7787 and whether it may be overturned in future political elections. The peer reviewer also thought that a 20-year ban on uranium mining may not be adequate to protect the cactus and its habitat with respect to recovery.

Our Response:

We relied on the best scientific and commercial data available at the time of our proposed rule to determine whether uranium mining is a significant threat to the Fickeisen plains cactus across its range. As of the date of publication, PLO 7787 remains in effect and our analysis of the impact of that Order is unchanged. No new information was provided during the comment periods on the threat of uranium mining to the Fickeisen plains cactus or its habitat. If new information becomes available in the future indicating that uranium mining is a significant threat to the Fickeisen plains cactus and its habitat, we will incorporate those findings and reconsider our conclusion in any future recovery planning efforts or 5-year reviews of the taxon.

(7)

Comment:

One peer reviewer acknowledged that off-road vehicle (ORV) use, road construction, and recreational uses within the habitat of

the Fickeisen plains cactus are increasing. The peer reviewer suggests however, that, without scientific documentation, the Service cannot fully quantify the current impacts to the species.

Our Response:

We agree with the peer reviewer that ORV use and its impact to the cactus and its habitat has not been investigated. We have very little evidence (three observations) over a 23-year period of cacti being damaged by ORV use or roadwork on lands managed by the Bureau of Land Management (BLM) and Navajo Nation. Because of the scarcity of information we cannot quantify the effects nor can we say that these actions rise to the level of significance such that they result in local or rangewide population declines.

(8)

Comment:

One peer reviewer stated that development on the Navajo Nation is imminent and possibly may be ongoing. The reviewer suggests the Service reconsider the determination that development is not impending.

Our Response:

We are aware that the Navajo Nation may be interested in developing areas along the rims of the Colorado River and/or Little Colorado River to increase tourism opportunities. We did not receive information describing a timeframe, commitment, or specifics related to commercial development projects on tribal lands and any potential impacts they may have on the Fickeisen plains cactus. We relied on the best available scientific and commercial data available at the time to determine whether commercial development was a threat to the Fickeisen plains cactus and its habitat. Information we received indicated potential future development was too speculative, and, therefore, we do not consider it to be a threat to the cactus at this time.

(9)

Comment:

One peer reviewer asked for clarification on

Factor D: Inadequacy of Existing Regulatory Mechanisms

and the rationale for our conclusion for the Fickeisen plains cactus. The reviewer pointed to the first paragraph in this section of the proposed rule (77 FR 60509, p. 60544) stating that there are no existing laws or regulations that address the threats to the cactus but the second paragraph states that legal and regulatory mechanisms which are in place appear to be adequate to protect the plant. The reviewer notes that, if conservation measures are largely voluntary throughout the range of the species, then it appears that the existing regulatory mechanisms are likely inadequate to protect the species.

Our Response:

The basis for Factor D is to review the existing regulatory mechanisms that apply to the acuña cactus and Fickeisen plains cactus. These mechanisms are then evaluated to assess whether they address any of the threats identified for each plant. For instance if the regulatory mechanism protects individual plant species, but does nothing to protect the habitat, then that mechanism does not address the threats, if there are threats to the habitat. We have clarified our discussion under Factor D in this final rule.

(10)

Comment:

One peer reviewer is concerned that information is lacking regarding threats from illegal collection of the Fickeisen plains cactus and feels that the Service is making a determination about the impacts of collection on this species prematurely.

Our Response:

As discussed in the rule, there have been no reported instances of illegal collection, nor have there been documented cases. We, therefore, relied on the best scientific and commercial data available at the time of listing, which indicated that illegal collection on the Fickeisen plains cactus is not a threat at this time. However, if information suggests that collection becomes a threat in the future, we will take that into account during recovery planning for the Fickeisen plains cactus.

(11)

Comment:

One peer reviewer commented that the distribution and range estimates for the Fickeisen plains cactus by NatureServe and Benson are too different and do not provide meaningful information. The reviewer suggested basing the range on current information of population distribution and habitat.

Our Response:

There have been two estimates of range: One by NatureServe in 2011, the other by Benson in 1982. As stated in the rule, we do not have certainty that these estimates delineate the range where the Fickeisen plains cactus is distributed. We conclude, however, that the current and historic distributions are very similar as no documentation suggests that additional populations occur outside of its known range. We, therefore, provided an estimate of range that includes the currently known populations.

Public Comments

(12)

Comment:

The U.S. Forest Service provided information clarifying the status of the Fickeisen plains cactus in areas that were considered to be occupied by the plant. They also provided information describing the attributes of occupied habitat.

Our Response:

The information demonstrated that one of the locations thought to be occupied by the Fickeisen plains cactus was erroneous. That site, Snake Gulch, located along the western boundary of the Forest is now considered to be unoccupied. We have included this information regarding the status of the population near the eastern boundary into the rule.

(13)

Comment:

A land management agency and a member of the public commented about a statement made in the proposed rule under Factor A—Livestock Grazing in regard to the increases and decreases of the North Canyon Fickeisen plains cactus plot on the Arizona Strip (77 FR 60509, p. 60536). The Federal agency stated that the proposed rule states that grazing has likely diminished the quality of suitable habitat on the Sunshine Ridge and North Canyon plots. This conclusion is based on population fluctuations and the absence of grazing on the North Canyon plot between 2001 and 2008, during which time the population increased. It is important to note that the population increased similarly between 1986 and 1991 while grazing was present in the area. It is, therefore, speculation to conclude without supporting data that grazing is causing population fluctuations or hindering population recovery.

Our Response:

During both wet and dry years, the BLM recorded increases in some populations. No weather data was recorded at the sites during these studies, and nearby weather station data is inadequate to draw conclusions. The monitoring was not designed to separate the effects of weather and cattle impacts to the plants; therefore, conclusions cannot be drawn. We agree with the commenter that we do not fully understand what contributed to the increase in plants in the North Canyon plot.

(14)

Comment:

We received comments indicating there are questions regarding the taxonomic validity of

Echinomastus erectocentrus

var.

acunensis.

In particular, there is concern that the variety

acunensis

may be subsumed into the more widespread species

E. johnsonii.

One comment suggests a need for further study, while the second requests justification for choosing one scientific name over another.

Our Response:

As stated in the proposed rule, the Cactaceae treatment in the Flora of North America (Zimmerman and Parfitt 2003, pp. 194-195) recognizes the entity as

E. erectocentrus

var.

acunensis.

A 2007 study by Baker indicated that all

Echinomastus

populations could be placed under a single taxon circumscribing an enormous amount of morphological variation, or they could be recognized as infraspecific taxa

under a single species. Baker's 2012

Echinomastus

treatment in the Intermountain Flora notes that further study is needed in order to properly circumscribe subspecific taxa. To date, no peer-reviewed publications state that

E. erectocentrus

var.

acunensis

should not be considered as a valid taxon; therefore, the Service accepts this nomenclature.

(15)

Comment:

One commenter suggested that the Service relied upon insufficient evidence of a threat to either cacti species and selectively overlooked uncertainties and data gaps, as well as evidence of increases in populations of these species. Specifically, they commented that listing is unwarranted because we do not have sufficient information on the abundance and health of either species, surveys vary by methodology and accuracy, and data is old and incomplete.

Our Response:

The Act requires that we use the best scientific and commercial data available regardless of the age of the information. In the proposed rule, we solicited the public for any new information on these species; while we received information clarifying what was published in the rule, no new population information was received. In some cases, the best available data is derived from different species with similar habitat requirements. We have used the best available scientific and commercial data, including results of numerous surveys, peer-reviewed literature, unpublished reports by scientists and biological consultants, and expert opinion from biologists with extensive experience with the species. We acknowledge that additional surveys and continued monitoring of existing plots would be valuable and should be considered as a recovery action for these species.

Based on our review of the best available scientific and commercial data, we have determined that both species warrant listing as endangered because they are in danger of extinction throughout all or a significant portion of their ranges. We determine whether any species is an endangered or a threatened species based on a five-factor threat analysis. For the acuña cactus, the threats to the species and its habitat result from the effects of drought and climate change; predation by native insect and small mammal predators; habitat destruction, modification, and degradation from United States-Mexico border activities (Factor A); and nonnative, invasive plant species issues (Factor A). In addition, the existing regulatory mechanisms in place do not directly address the threats to the species. For the Fickeisen plains cactus, the threats to the species and its habitat result from habitat destruction, modification, and degradation from livestock grazing (Factor A) in combination with predation by small mammals (Factor C) and natural environmental variability and the effects of climate such as drought. When combined with the above-mentioned threats, small population size (Factor E) likely exacerbates the effects of these threats on the Fickeisen plains cactus. In addition, the existing regulatory mechanisms are not ameliorating threats to the species. Please refer to the Summary of Factors Affecting the Acuña Cactus and Summary of Factors Affecting the Fickeisen Plains Cactus for more detailed information.

(16)

Comment:

One commenter believes the Service is attributing population decline in both species due to drought and speculates this drought is caused by climate change that may happen in the future.

Our Response:

As is the case with all models, there is uncertainty associated with climate change projections due to assumptions and scale used and other features of the models. Projected future drought would increase an already existing impact of long-term drought on these species. The Service finds that drought over the past 30 years within the region has negatively impacted seedling recruitment and adult survivorship. In addition, projections of future climate in the region include continued drought and warming winters. Therefore, the continued effects on seedling recruitment and adult survivorship are likely to continue into the future. The Service will continue to follow and assess the science behind climate change and update our summaries as new information is published.

(17)

Comment:

One commenter is concerned that should either plant be listed, the final listing rule could be misused to impose undue burdens on American industries or activities that produce greenhouse gas emissions because the proposed rule identified the future effects of climate change as a threat to both species. The commenter requested that, if listing occurs at all, these cacti should be listed as threatened and a special rule should be created under section 4(d) of the Act establishing limits on the application of section 9 take prohibitions similar to the special rule for the polar bear under section 4(d) of the Act (December 16, 2008; 73 FR 76249).

Our Response:

While the Service may find that the effects of climate change are threats to species, regulation of greenhouse gas emissions is beyond the scope of the Act. The term “threatened species” means any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range. Alternatively, the term “endangered species” means any species which is in danger of extinction throughout all or a significant portion of its range. We have determined both acuña cactus and Fickeisen plains cactus are in danger of extinction throughout all or a significant portion of their range and, therefore, meet the definition of endangered species under the Act.

Listing either species as threatened is not the appropriate determination because the threats described are severe enough to create the immediate risk of extinction. As described in the Determination for the Acuña Cactus, the combination of declining rainfall, ongoing drought conditions, and the effects of climate change is expected to continue the documented trend of mortality exceeding recruitment across all populations of the acuña cactus. When mortality exceeds recruitment in a population, the result is often a declining population. Given this, we consider none of the populations to be stable or secure. The factors significantly threatening the species are not expected to be abated in the foreseeable future, and some populations may have decreased to levels where they are no longer viable. For these reasons, we have determined the acuña cactus meets the definition of an endangered species under the Act. Similarly, as described in the Determination for the Fickeisen Plains Cactus, the effects from climate change are expected to continue the documented trend of mortality exceeding recruitment across all populations. This, in combination with the other factors significantly threatening the species, leads us to conclude that the threat of extinction is high and immediate for the Fickeisen plains cactus, thus warranting a determination of endangered species status rather than threatened species status for the Fickeisen plains cactus.

If a species were listed as threatened, the Secretary can issue a special rule under section 4(d) of the Act if deemed necessary and advisable to provide for the conservation of the species. A section 4(d) rule is designed to provide for conservation of species through allowing take of listed species under certain allowable activities. That is, take, as defined under the Act, if it occurs under an allowable activity, would not be a violation of the Act. In the case of these two cacti, the Service

is not able to issue a 4(d) rule since we have determined both meet the definition of an endangered species.

(18)

Comment:

One commenter suggested the proposed rule underestimates the extent of the range of the acuña cactus, noting in particular the population of

Echinomastus

species found in 2009 in the Bighorn and Littlehorn Mountains, which was not included in analysis for the acuña cactus.

Our Response:

We are aware of the populations of acuña cactus in the Bighorn and Littlehorn Mountains. Morphometric analysis of Baker (2007, p. 11) suggests that, while individuals among these populations share many characters in common with

E. erectocentrus

var.

acunensis,

they also show characteristics of var.

lutescens.

Therefore, as the identity of these populations has not been verified, we did not include these populations in our evaluation of the status of the species.

(19)

Comment:

One commenter is concerned that the Service relied on only a few of the known populations of acuña cactus to derive data for decline and used inconsistent monitoring efforts and a lack of statistically robust methods to estimate total abundances and changes in abundance over time. The commenter feels that information is lacking, and a decision to list the acuña cactus as endangered is premature. The commenter provided four examples of population decline data used in this rule and which they dispute: (1) Rigorous sampling of the overall population at OPCNM is needed and prior estimates of population numbers are speculative; (2) sampling at the Coffeepot Mountain population has been inconsistent and no meaningful conclusion regarding this population can be drawn; (3) the Mineral Mountains population counts from the 1990s do not indicate type of sampling or area covered and, therefore, should not be compared with 2011 sampling; and (4) upon their own visit to the population at Indian Village Hill, they found 33 individuals, as compared to the Service visit of 2011 which found just 8 individuals, illustrating that individuals were being missed in surveys. The commenter acknowledges there appears to be a decline in some of the monitored populations of acuña cactus, but suggests there is also evidence that small populations are viable and relatively stable.

Our Response:

We have used the best scientific and commercial data available; while these references may include varying survey and monitoring methodologies, they nonetheless provide important data upon which we can base our analysis. We acknowledge that additional surveys and continued monitoring of existing plots would be valuable and should be considered as a recovery action for these species. We address the commenter's examples here: (1) In addition to overall population estimates, monitoring plots within Organ Pipe Cactus National Monument (OPCNM) show a pronounced decline in acuña cactus numbers which outweighs recruitment and is a serious concern for park managers (NPS 2012, p. 1; Holm 2006, p. 2-2). (2) We received public comments during the first comment period which indicated that the Coffeepot Mountain acuña cactus population was revisited by OPCNM staff in 2008. The population was censused in 1987 and again in 2008, and total living plants at that location decreased from 310 to 77. (3) The same BLM botanist was involved in the 1990s, 2002, 2008, and 2011 acuña cactus survey of the same ridgelines in the Mineral Mountains. Original surveys indicated more than 100 individuals present; in 2011 these and a fourth new population on a nearby ridgeline totaled 33 living plants (Service 2008a, entire; Service 2011b, p. 1). (4) At Indian Village Hill, researchers found 102 individuals in 1996. The Service acknowledges that it should not have utilized the 2011 Service report indicating current population numbers at this location. The Service report indicated that approximately 8 individuals were noted at this site (Service 2011a, p. 1); however, a full census was not conducted. Nevertheless, the 2013 census of the commenter found 33 individuals, clearly fewer than 102 found in 1996. These and other examples (refer to the “Abundance and Trends” of the acuña cactus section of the rule) all illustrate a marked decline in the number of individuals censused over time. There is also evidence that recruitment (the number of juveniles seen) is not keeping up with the number of dead plants counted in any location.

Background

In the proposed listing rule, we provided a description of each species, their life history, and their habitat; an evaluation of listing factors for each species; and our finding for the species. In this final listing rule, we include only those sections that have been revised as a result of the public comments we received and to reflect the best scientific and commercial data available.

Acuña Cactus

It is our intent to discuss below only those topics directly relevant to the listing of the acuña cactus as an endangered species in this section of the final rule. The biology and habitat sections remain unchanged since publication of the proposed rule. Please refer to the proposed listing rule for the acuña cactus and Fickeisen plains cactus (77 FR 60509; October 3, 2012) for a detailed description of the biology and habitat of the acuña cactus. We have updated the “Species Description”, “Taxonomy”, “Distribution and Range”, and “Abundance and Trends” sections below as a result of information received from the public during the public comment periods.

Species Description

The acuña cactus is a small, spherical cactus, usually single-stemmed, that can be up to 40 centimeters (cm) (16 inches (in)) tall and 9 cm (3.5 in) wide (Arizona Rare Plant Guide Committee 2001, unpaginated; Zimmerman and Parfitt 2003, pp. 194-195). The acuña cactus has 11 to 15 radial spines up to 2.5 cm (1.0 in) long and 3 to 4 mauve-colored, up-turned central spines up to 3.5 cm (1.4 in) long (Arizona Rare Plant Guide Committee 2001, unpaginated; Zimmerman and Parfitt 2003, pp. 194-195). Rose, pink, or lavender flowers 3.6 to 6 by 4 to 9 cm (1.4 to 2.3 by 1.6 to 3.5 in) are produced in March (Arizona Rare Plant Guide Committee 2001, unpaginated; Zimmerman and Parfitt 2003, pp. 194-195). The fruits, which are held in place by a tight mesh of spines, are pale green, are 1.25 cm (0.5 in) long, and contain small, nearly black seeds (Felger 2000, p. 208). The fruits ripen in April (Arizona Rare Plant Guide Committee 2001, unpaginated) and as they dry, they split longitudinally, exposing the seeds (Morawe 2012, pers. comm.).

Taxonomy

This species was originally described in 1953 by W.T. Marshall as

Echinomastus acunensis

(Marshall 1953, pp. 33-34). It is known by many synonyms, including

Sclerocactus erectocentrus

var.

acunensis

(Coulter) Taylor and

Neolloydia erectocentra

(W.T. Marshall) var.

acunensis

L. Benson (Arizona Game and Fish Department (AGFD) 2004, p. 1). The Cactaceae treatment in the Flora of North America (Zimmerman and Parfitt 2003, pp. 194-195) recognizes the entity as

E. erectocentrus

var.

acunensis.

The other variety,

E. erectocentrus

var.

erectocentrus

(needle-spine cactus), is also recognized as a valid taxon in the Flora of North America. The two varieties are generally considered to be morphologically distinct and

geographically isolated, but there have been questions regarding the morphology of some individuals (AGFD 2004, p. 6). To address those concerns, the Service funded a project to analyze the morphological distinctness of the two varieties, which was completed in January 2007. The results of this study suggest that there are four distinct taxonomic groups, including the separation of variety

acunensis

and variety

erectocentrus

(Baker 2007, pp. 19-21). Baker (2007, p. 20) recommended nomenclatural changes, based on the International Rules of Botanical nomenclature, but formal name changes were not proposed in his study. Since that time, Baker collected additional morphology data from other

Echinomastus

populations and concluded in his 2012 Intermountain Flora

Echinomastus

treatment, that all varieties of

Echinomastus

be combined into a single species

E. johnsonii

(Baker 2012, p. 445). In this treatment, however, Baker notes that further study is needed in order to determine if separating the species into varieties may be warranted (Baker 2012, p. 446). To date, there are no peer-reviewed publications stating that

E. erectocentrus

var.

acunensis

should not be considered as a valid taxon. Therefore, we accept Baker's 2007 work and the Flora of North America, which separate the acuña cactus from the needle-spine cactus as valid and distinct taxa separated morphologically and geographically.

Distribution and Range

The acuña cactus populations are known from Maricopa, Pima, and Pinal Counties in Arizona and from Sonora, Mexico (AGFD 2004, p. 2). In western Pima County, plants are known from the Puerto Blanco Mountains and adjacent Aguajita Wash on National Park Service (NPS) lands within OPCNM; from the Sauceda Mountains on Bureau of Land Management (BLM) and Tohono O'odham Nation lands; from Department of Defense military lands on the Barry M. Goldwater Gunnery Range (BMGR); and from private lands near Ajo. In Maricopa County, the acuña cactus is known from the Sand Tank Mountains on BLM lands within the Sonoran Desert National Monument. In Pinal County, plants are known from Mineral Mountain on BLM, State, and private lands. In Sonora, Mexico, the acuña cactus occurs on Reserva de la Biosfera El Pinacate y Gran Desierto de Altar (Pinacate Biosphere Reserve), communal ejido lands, and private ranches. Available information indicates that the current range of this species does not differ from the historical range, with the exception that the current Ajo populations likely had been part of a larger population that occurred before mining activity began there (Rutman 1996b, pers. comm.; Rutman 2007, p. 7). However, there are no survey records for this species in the area prior to mining activity.

Abundance and Trends

As the number of dead individuals documented within acuña cactus populations has increased greatly since study began in the 1970s, it is important to track the number of healthy, unhealthy, and dead individuals. This not only allows us to document trends in total plant numbers, but also can help in our understanding of the cause and extent of mortality. A discussion of abundance and trends of acuña cactus populations on Federal, State, and private lands, along with lands in Sonora, Mexico, is presented below.

Federal Land—National Park Service

Organ Pipe Cactus National Monument

—There is one large area of approximately 1,326 ha (3,277 ac) within OPCNM that contains as many as 2,000 acuña cactus individuals (Rutman 2011, pers. comm.; AGFD 2011, entire). In 1981, this population was estimated to contain 10,000 individuals (Buskirk 1981, p. 3). Within this area, two 20-by-50-m (66-by-164-ft) permanent monitoring plots were established in 1977, with the aim of investigating growth, mortality, and recruitment of this species. Between 1977 and 1981, mortality reached 31 percent in the plots (Phillips and Buskirk 1982, p. 2). Two more plots were added in 1983, and two more in 1988. From 1988 through 1991, the population was thought to be stable or increasing (Johnson

et al.

1993, p. 172), with 446 individuals found in the 6 plots by 1991 (Holm 2006, p. 6). From 1993 through 2012, annual mortality was variable, but exceeded recruitment in most years (NPS 2012, p. 2). In 2012, the total number of individuals recorded in the 6 plots was 38 adults and 15 juveniles (NPS 2012, entire).

In order to verify the identification and location of plants, specimens are collected, pressed, and placed on sheets that are stored in herbaria. A 1952 herbarium collection from a second location within OPCNM is evidence that a second disjunct population of the acuña cactus occurred historically within OPCNM. The information associated with this collection states the plants were located south of Dripping Spring within 3 m (10 ft) of the U.S.-Mexico border; an exact location was not provided. Although staff at OPCNM were unaware of this herbarium collection, they state that the general area of its collection has been visited during surveys for sensitive cultural and natural resources, as well as for buffelgrass; no acuña cactus plants were noted (Morawe 2012, pers. comm.). We do not know if the population or a seedbank exists at this location; however, we do know that lands immediately adjacent to the border have changed significantly in recent decades with the creation of border fencing, vehicle barriers, and Border Patrol service roads. Although this population likely once supported enough individuals to warrant collection for herbaria, it is likely this population no longer exists at this location. During a public comment period, we requested any information about the status of the acuña cactus at this location; no additional information on the cactus was received.

Federal Land—Bureau of Land Management

Sauceda Mountains

—Within the Coffeepot Area of Critical Environmental Concern (ACEC), there are several small acuña cactus populations, each on less than 2 ha (5 ac) of land.

In 1982, the BLM (Phoenix District) established three 20-by-50-m (66-by-16- ft) monitoring plots on Coffeepot Mountain. These plots were visited, and data were collected periodically between 1982 and 1992. In 1982, researchers found 157 living and 3 dead plants within the plots. Over the years of study, many new recruits were found; however, there was also ongoing mortality with newly dead individuals documented each year. BLM staff reported a precipitous decline of this population in 1989 (Johnson 1989, p. 1). A note to the file in 1991 stated that many individual plants were missing, dead, or dying, and that there appeared to be little regeneration in this population (BLM 1991, p. 1). By the monitoring visit in 1992, researchers recorded 150 plants dead, 22 plants missing and presumed dead, and 150 plants within the plots that were either healthy or in some stage of decline (Butterwick 1982-1992, entire). The plots have not been formally measured since 1992, but the BLM has visited this site 21 times since then to assess general health and threats to the population. Field notes indicate that few juveniles were seen in 2008, and no juveniles were seen in 2009; no mention of juveniles was made in 2010 or 2011 (Anderson 2011, p. 2). The site was not visited in 2012.

A complete census of individual acuña cacti from both within and nearby the Coffeepot Mountain plots in 1987 found 310 living and 332 dead plants (Rutman

et al.

1987, p. 2). In 2008, staff of OPCNM censused the number of individuals from both within and nearby the plots and found 77 living and 80 dead plants (Morawe 2012, pers. comm.). The loss of 252 dead plants during this time is also of interest, as it shows that the cage-like spinal remains of acuña cacti do not persist in the environment for extended periods.

In 2006, a second population, estimated to be between 50 and 100 individuals, was located 1.2 kilometers (km) (0.75 miles (mi)) northwest of the Coffeepot Mountain monitoring plots in Ryans Canyon (Rutman 2006, p. 2). Rutman (2006, entire) did not mention size class or health of this population. This site has not been revisited. In 2006, a third population was discovered 1.4 km (0.87 mi) to the northeast of the Coffeepot Mountain monitoring plots. Approximately 30 acuña cacti were noted there at the time; 25 percent mortality was reported 1 year later (Anderson 2011, p. 1). An October 2011 site visit by Service and BLM botanists revealed 23 adult and 2 juvenile living and 15 dead plants at this location (Service 2011a, p. 3). A fourth population was discovered in March 2011, in a location near the third population; 10 plants were noted. No indications were given as to the age class structure or health of this population (Anderson 2011, entire).

At an acuña cactus site the BLM calls Little Ajo Mountains, southeast of the New Cornelia Mine on less than 0.4 ha (1 ac), the population has fluctuated from 5 plants in 1997, to 7 plants in 2001, to 7 plants in 2006, to 11 plants in 2007, to 7 plants in 2008, and finally to 12 plants (including 5 very small plants) in 2011 (Rutman 2006, p. 2; Anderson 2011, entire; Service 2011a, p. 1). In 2013, the site was visited and 12 plants were located, 5 of which were reported to be uprooted and 2 were juvenile (Westland Resources 2013, p. 3). Westland Resources noted that the five individuals that were uprooted were lying on their side and may have been the target of herbivory or may have been knocked over by a passing animal (2013, p. 3).

Sonoran Desert National Monument

—In 2006, approximately 200 individuals were reported from the Sand Tank Mountains in an area less than 25 ha (61.8 ac) in size. In 2007, the site was revisited, and 4 groups of individuals accounting for 125 of the approximately 200 individuals were mapped (Anderson 2012b, pers. comm.; Anderson 2011, p. 2). No indications were given as to the age class, structure, or health of this population (Anderson 2011, entire). This site has not been revisited.

Mineral Mountain

—There are 3 individual acuña cacti growing on BLM land adjacent to 30 living plants and 22 dead plants on Arizona State Trust lands (State land). This population is discussed collectively below under “State Land”.

Federal Land—Department of Defense

Barry M. Goldwater Gunnery Range

—In 1997, a single adult individual was reported from just north and outside of the populations in the Coffeepot ACEC (Geraghty

et al.

1997, p. 5) within Department of Defense (DOD) managed lands on the BMGR. This site was revisited in 2012, but no plants were located (Whittle 2012a, pers. comm.). It is unknown if the one previously located individual has been extirpated or was missed during the survey, nor is it known if a seedbank persists at this location.

State Land

Mineral Mountain

—Plants were collected by S. Hart in 1992, from the population straddling BLM and State land east of Florence (University of Arizona Herbarium 2011, entire). There were no details of the number of individuals seen, just a map with three locations. In the 1990s, the BLM revisited this site and estimated 100 individuals were scattered across 3 ridgelines (Service 2008a, p. 1). In 2008, the Service and BLM searched this area finding fewer than 20 living and many dead plants; no young plants were seen. In 2011, the Service and BLM botanists revisited the location and found 33 living and 22 dead plants scattered across 4 adjacent ridgelines on less than 5 ha (12.4 ac) of land; no juveniles were found (Service 2011b, p. 1).

Ninety-Six Hills

—This population is in the vicinity of Florence on less than 1 ha (2.47 ac) of land. Parfit (1977, p. 1) noted that plants here were common, but very localized. Many plants of various ages and sizes were noted, as well as many dead plants. Engard (1977, p. 1) noted many seedlings and mature plants and also that the plants were abundant locally. Rutman and Krausman (1988, p. 1) found 29 live plants and 6 dead plants in a 2-hour survey in the same general area. Breslin (2008, pp. 3-5) reported that in over 60 hours of survey effort in the area he had located 45 plants, 1 seedling, and 17 dead plants. On March 20, 2008, the Service plant ecologist found 11 live plants and 10 dead plants in a 3-hour survey. In the same general area, C. Butterworth (2008, pers. comm.) found 32 live plants, of various sizes, except seedlings. He noted that seedlings were very noticeably absent. A 2011 2-hour survey by three Service and BLM botanists revealed no living and two dead adults in this same general area (Service 2011b, p. 3). Because this population was not mapped with Geographic Information Systems, it is impossible to know if survey efforts in 1977, 1988, 2008, and 2011 were all conducted in the exact same location within this general area. Therefore, it is not possible to conclude that this population has been extirpated.

Private Land

Ajo Area

—The combined area of these multiple sites is less than 0.4 ha (1 ac) (Rutman 2007, p. 1).

An isolated population near Darby Wells was first reported by Heil and Melton (1994, p. 14). Fewer than 10 plants were found at this site in 2007 (Rutman 2007, p. 4). There is no record if juveniles were among the plants found. The site has not been revisited.

On Indian Village Hill, there were 102 plants in 1996, when the population was first recorded (Rutman 1996b, pers. comm.). In 2006, 30 living and 33 dead plants were found; in 2007, fewer than 40 plants were found (Rutman 2006, p. 1; Rutman 2007, p. 4). There is no record if juveniles were among the plants found in either year. In 2011, Service and BLM botanists counted eight living and seven dead plants in a small area that was surveyed; no juveniles were found (Service 2011a, p. 1). In 2013, biologists from Westland Resources did a complete survey of the area and found 33 live and 8 dead individuals (Westland Resources 2013, p. 3). During this survey, they also discovered a single individual growing nearby across the road.

There were 16 live and 19 dead acuña cacti on Weather Tower Hill in 2006 (Rutman 2006, p. 1). There is no record if juveniles were among the plants found. The site was revisited in 2013 by Westland Resources biologists; 17 living and 26 dead individuals were located (Westland Resources 2013, p. 2). During this survey, they also discovered a separate subpopulation 200 m (656 ft) from the known population containing 10 living (including 1 juvenile) and 5 dead individuals (Westland Resources 2013, p. 2).

Florence Area

—Roadside populations occur on less than 0.4 ha (1 ac) collectively; any additional populations that may be present on private land occur on an unknown quantity of land.

Roadside Population One—The 2011 site visit revealed nine living and two dead individuals; no juveniles were found, though all nine were young healthy individuals (Service 2011b, p. 2).

Roadside Population Two—The 2011 site visit revealed two living and two dead individuals; no juveniles were found (Service 2011b, p. 2).

There may be other locations on private lands unknown to Service or BLM botanists.

Sonora, Mexico

Felger (2000, p. 208) noted the occurrence of the acuña cactus between 3 and 18 km (2 and 11 mi) southwest of Sonoyta along the Peñasco highway; no population estimates were made. Surveys of 7 acuña cactus populations from an area from 2009 through 2010 revealed 659 living and 942 dead plants growing on approximately 1,700 ha (4,200 ac) (Pate 2011, pers. comm.; Pate 2011, map 1 and map 2). Pate (2012a, pers. comm.) noted seeing a few small seedlings among these plants. From 2012 to 2013, researchers located 18 additional populations of acuña cactus in the vicinity of, but not within, those censused in 2009-2010 (Van Devender 2012, pers. comm.; Van Denvender 2013, pers. comm.). In these surveys, an additional 371 living and 801 dead individuals were counted; a few small living plants were noted (Van Devender 2012, pers. comm.; Van Devender 2013, pers. comm.). The total land area of the general region containing all 25 known populations in Sonora is roughly 6,900 ha (17,050 ac).

Summary

Presented below is the total estimate of living, dead, and juvenile acuña cactus plants in populations visited over multiple years, including census results from 2011 through 2013, and from previous years if sites have not been revisited or population estimates not updated. Notable trends are the large amount of mortality within the populations that have been visited more than once, high numbers of dead individuals within many populations visited once, and the low numbers of juvenile plants in all populations.

• NPS—2,000 plants, or 55.4 percent of known individuals; estimated in 2011 by OPCNM staff. This population estimate is down from 10,000 individuals estimated at this location in 1981. Within the OPCNM plots, the number of recorded individuals peaked in 1991, with 165 adult and 281 juveniles counted. In 2012, researchers noted 38 adult individuals and 15 juveniles within these plots (NPS 2012, p. 1).

• Sonora, Mexico—1,030 plants or 28.5 percent of known individuals; estimated from 2009 to 2010 and 2012 to 2013 surveys. During surveys of these plants, an additional 1,743 dead plants were located among the living. There are no previous estimates from these populations. A few juvenile plants were noted during both survey periods.

• BLM—422 plants, or 11.7 percent of known individuals; estimated from 2011 and other recent surveys. At Coffeepot Mountain within the largest BLM population, 310 living and 332 dead individuals were recorded from both within and nearby established plots in 1987. By 2008, this population was reduced to 77 living and 80 dead plants noted within and nearby established plots. No juveniles were noted since 2008, when a few were seen.

• Private Land—81 plants (70 near Ajo and 11 near Florence), or 2.2 percent of known individuals; estimated from 2013 and other recent surveys. A single population that was revisited on several occasions showed a total population of 102 individuals in 1996; in 2006, 30 living and 33 dead plants were found. In 2013, researchers recorded 33 plants from this population.

• State Land—75 plants, or 2.1 percent of known individuals; estimated from 2011 surveys. At one location in the 1990s, the population was estimated to be 100 individuals; in 2008, only 20 living and many dead plants were found with no juveniles seen. In 2011, researchers recorded 30 living plants, including a new subpopulation previously not recorded. No juvenile plants were located in 2011. At a second location, in 1977, plants were considered common but localized, and the site supported many plants of various ages and sizes. Surveys of this area in 2008 resulted in the location of 45 adult plants with no juveniles found. In 2011, no living plants and two carcasses were located in this same area, though surveys were not as thorough as in 2008; we use the 2008 number of 45 individuals for population estimates herein.

• Military BMGR—1 plant, or less than 0.03 percent of known individuals in 1997; this individual was not relocated in 2012.

Summary of Factors Affecting the Acuña Cactus

Section 4 of the Act (16 U.S.C. 1533), and its implementing regulations at 50 CFR part 424, set forth the procedures for adding species to the Federal List of Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of the Act, we may list a species based on any of the following five factors: (A) The present or threatened destruction, modification, or curtailment of its habitat or range; (B) overutilization for commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) the inadequacy of existing regulatory mechanisms; and (E) other natural or manmade factors affecting its continued existence. Listing actions may be warranted based on any of the above threat factors, singly or in combination. Each of these factors is discussed below.

Factor A. The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range

Based on the habitat characteristics described above, potential factors that may affect the habitat or range of the acuña cactus are: (1) Urban development and site degradation; (2) livestock grazing; (3) border activities; (4) nonnative, invasive plant species issues; (5) mining; and (6) drought and climate change.

Urban Development and Site Degradation

The immediate threats from urban development include the direct loss of individuals and habitat. Indirect impacts of urban development include fragmentation of acuña cactus and associated pollinator populations, which can reduce genetic vigor of the cactus and result in degradation and fragmentation of habitat adjacent to development. When development occurs, there is also an increased use of habitat for recreational activity, which may also deplete habitat and result in mortality of individuals. The acuña cactus populations in OPCNM and the Sonoran Desert National Monument are protected from the immediate threats associated with urban development due to their National Monument status. National Monuments are lands set aside and managed to protect the natural and cultural resources within; development is minimal, though some site degradation may still occur.

To meet the country's energy demands, there has been a recent emphasis by the Federal Government to use BLM lands for development of renewable energy. Currently, there are no planned solar or wind energy projects on or near populations of the acuña cactus in the Sauceda, Sand Tank, or Mineral Mountains (Werner 2011, pers. comm.). However, a solar field has recently been constructed on patented mine lands in the Ajo area (Morawe 2012, pers. comm.). Most populations on BLM lands are remotely

located and relatively inaccessible; therefore, we do not anticipate development in these areas.

As Arizona's population is expected to continue to grow in the future, both Pinal County and the State Land Department are promoting urban development in the vicinity of Florence (Pinal County 2009, pp. 4, 60, 94; Guthrie

et al.

2011, p. 1). When the housing market rebounds, it is likely that additional State land in this area will be sold for urban development (Pinal County 2009, p. 42; Guthrie

et al.

2011, p. 2). In the vicinity of Florence, there are no current plans for development of State land known to support acuña cacti. Private lands near Florence containing acuña cacti populations have been for sale as subdivided 16.2-ha (40-ac) parcels for many years. With the recent economic downturn, it is unlikely this land will be sold in the near future. The only known private land populations where access is readily available are at 3 sites near Ajo, totaling less than 0.4 ha (1 ac) and supporting fewer than 40 individuals in total (Rutman 2006, p. 1; Rutman 2007, pp. 1, 4; Service 2011a, p. 1). In most of the privately owned locations, the sites are littered with broken glass, bottles, and trash; however, plants appear little impacted by this habitat degradation (Service 2011a, p. 1; Service 2011b, p. 2).

Indirect urbanization effects to the areas that support the acuña cactus include ORV activity, which has been reported on BLM lands near both Ajo and Florence. These reports, however, showed no impact to the acuña cactus populations in 1994 (Heil and Melton 1994, pp. 15-16), although habitat degradation and direct loss of individuals is possible from this activity. In 1989, the BLM closed the Coffeepot ACEC to recreational ORV use (BLM 2012a, p. 2-195). In 2002, the BLM prohibited ORV use on the Sonoran Desert National Monument, and, in 2005, affirmed a restriction to designated, established, routes in the Sand Tank Mountains area (BLM 2012a, p. 2-181). In 2012, the BLM Lower Sonoran Field Office released Resource Management Plans (RMPs) for the Sonoran Desert National Monument and the Lower Sonoran Decision Area (BLM 2012b, c, entire).

The Lower Sonoran Decision Area encompasses approximately 930,200 acres of BLM-administered land in south-central Arizona, mostly south and west of Phoenix, and extends south to the United States-Mexico border, west to the Yuma County line, and as far east as the town of Globe. On the Sonoran Desert National Monument, motorized vehicle use is limited to designated roads or primitive roads (BLM 2012c, p. 2-78). Throughout the Lower Sonoran Decision Area, including the Coffeepot ACEC, travel is limited to existing roads and trails (based on current BLM route inventories) until route designations are completed. When designations are completed, travel will be restricted to designated roads, primitive roads, and trails (BLM 2012b, p. 2-113). These new RMPs for the Lower Sonoran Decision Area and the Sonoran Desert National Monument will remain in effect for the next 15 to 20 years (Foreman 2011, pers. comm.). The impacts of ORV activity on State or private lands are unknown; for ORV activity within the border region, see the discussion below of border activities.

In Sonora, Mexico, scattered populations of the acuña cactus occur within 10 km (6.2 mi) of the town of Sonoyta. Although the area is reported to be little-used and unoccupied except by drug and human smugglers (Pate 2011, pers. comm.), in recent decades and as a result of human demand, the Sonoyta region has been heavily impacted by

Olneya tesota

(ironwood) and

Prosopis velutina

(mesquite) woodcutting for coal production, brick foundries, and tourist crafts, and the lands' subsequent conversion to exotic grasslands for cattle grazing (Suzán

et al.

1997, pp. 950, 955). This activity has affected more than 193,000 ha (478,000 ac) of lands in the Sonoyta region (Nabhan and Suzán 1994, p. 64). In a study of ironwood extraction in northern Mexico, the Sonoyta study sites exhibited the highest number of damaged and dead trees and had the lowest associated plant diversity (Suzán

et al.

1996, p. 642). It is likely that habitat parameters for the acuña cactus populations in Sonora are impacted by this activity, particularly because ironwood is considered a dominant associate of the acuña cactus (Phillips

et al.

1982, p. 5) and may serve as a nurse plant for a variety of cacti (Suzán

et al.

1996, p. 635).

In addition, the actions of harvesting, burning, loading, and transporting wood and charcoal can result in running over individual acuña cactus and causing injury or mortality of plants, if such actions occur in areas supporting the acuña cactus. Also, human population growth and development in the border region between the United States and Mexico has risen in recent decades (Brown and Caldwell 2008, pp. 1-6); it is reasonable to conclude that the direct and indirect effects of urbanization are likely to increase threats to the acuña cactus populations in this region. The acuña cactus populations are currently split by a major highway, Interstate 8, and a power transmission line; many plants occur within 200 m (660 ft) of these corridors (Pate 2011, map 1 and map 2).

In summary, the direct and indirect effects of urbanization are threats to a portion of the known populations of the acuña cactus. However, these effects are currently limited to the acuña cactus populations in the vicinity of Ajo and Florence in the United States and in the immediate border region of Sonora, Mexico. These areas collectively make up roughly 31 percent of known living acuña cactus individuals across the range of the acuña cactus, including Mexico. The majority of the range in the United States is protected from urban development because populations are on Federal lands, where little or no development will take place. In addition, most populations of the acuña cactus are relatively remote or otherwise protected from the effects of urbanization. We conclude that urban development and site degradation is not currently a threat to any entire population of the acuña cactus. As a result, based on our review of the available information, we conclude that the direct and indirect effects associated with urbanization are not threats to the acuña cactus and its habitat.

Livestock Grazing

In general, grazing practices can change vegetation composition and abundance and cause soil erosion and compaction, reduced water infiltration rates, and increased runoff (Klemmedson 1956, p. 137; Ellison 1960, p. 24; Arndt 1966, p. 170; Gifford and Hawkins 1978, p. 305; Waser and Price 1981, p. 407; Robinson and Bolen 1989, p. 186; Holechek

et al.

1998, pp. 191-195, 216; and Loftin

et al.

2000, pp. 57-58). These anticipated effects leave less water available for plant production (Dadkhah and Gifford 1980, p. 979). In addition, livestock can step on or knock over individual acuña cactus. Although other species of cacti may be good survival forage for livestock (Vega- Villasante

et al.

2002, p. 499), herbivory of the acuña cactus has not been reported. Livestock grazing levels and habitat condition vary greatly between populations due to varied land ownership and management. A discussion of livestock grazing practices within the acuña cactus range on Federal, State, and private lands, along with lands in Sonora, Mexico, is presented below.

Federal Land—National Park Service

Organ Pipe Cactus National Monument

—Beginning in the early

1900s and continuing through the 1970s, lands within OPCNM were grazed heavily, with as many as 3,000 head of cattle and hundreds of burros present at a time when carrying capacity was estimated to be 314 cattle per year (Rutman 1997, p. 364; NPS 2011b, entire). Grazing by domestic animals was halted per NPS policy and has not occurred within OPCNM since 1976 (NPS 1997, p. 33). Lands here continue to recover slowly after loss of soils and vegetation and may take many decades or centuries to recover fully (NPS 2001, pp. 27, 124). Currently, OPCNM supports the largest population of the acuña cactus (55.4 percent of known living acuña cactus individuals), and we are not aware of historical effects to the population as a result of past livestock grazing.

Federal Land—Bureau of Land Management

Sauceda Mountains

—All four populations of the acuña cactus on BLM lands in the Sauceda Mountains have been managed since 1988 in the Coffeepot ACEC, which attempts to apply grazing management practices to ensure perpetuation of botanical diversity within the area and prohibits the development of livestock facilities that would serve to increase livestock use within the area (BLM 2011, p. 141). Collectively these four populations make up 5.9 percent of known living acuña cactus individuals. In 1987, when speaking of the then proposed Coffeepot ACEC, Olwell (1987, p. 1) noted relatively pristine conditions with no immediate threat to the acuña cactus plants. At that time, however, the population of acuña cactus within the Coffeepot ACEC in the vicinity of permanent monitoring plots was reported to have substantial animal activity from cattle, javelina, and jackrabbits, with browsing, grazing, and soil disturbance noted (Rutman

et al.

1987, p. 2). Anderson (2011, entire) noted no habitat impacts from grazing in this population during yearly visits from 1994-2011. This population is the farthest population from a single cattle tank (see below) within the ACEC and, therefore, is less subjected to livestock pressure.

On BLM land south of Ajo, five individuals were noted to be uprooted and lying on their side (Westland Resources 2013, p. 3). It was speculated these individuals were either predated upon or had been knocked over by a passing animal. It is unknown if cattle were responsible for these losses.

Sonoran Desert National Monument

—In 1970, a cattle tank named Conley Reservoir was established within the Coffeepot ACEC boundary prior to the ACEC designation and remains today (Foreman 2012, pers. com.). A population of acuña cactus very near this tank was visited by the BLM botanist in 2010, who found abundant prickly pear (

Opuntia

spp.), which are known to increase with disturbance and are often cited as an indicator of poor range condition (Johnson 2000, entire; Anderson 2011, p. 2). A site visit in 2011 by Service and BLM botanists found habitat impacts such as soil disturbance from both cattle and feral burros; however, no acuña cactus plants appeared to be directly impacted by these animals (Service 2011a, p. 3). Feral burros also impact vegetation on neighboring military lands (see

Barry M. Goldwater Gunnery Range

section below).

The BLM's 2012 Lower Sonoran Decision Area RMP allocates all of the land within the Childs Allotment, within which the Coffeepot ACEC lies, as available for livestock grazing (BLM 2012b, p. 2-82). According to this document, past grazing levels (3,802 animal unit months/317 cows yearlong) and type of use (perennial/ephemeral) will remain the same, and livestock facilities that would increase livestock use within an area of known or newly discovered populations of acuña cactus will not be developed (BLM 2012b, p. 2-124). This management plan will remain in effect for 15 to 20 years (Foreman 2011, pers. comm.).

Sonoran Desert National Monument

—In 2001, Presidential Proclamation 7397 (Clinton 2001, entire) created the Sonoran Desert National Monument; one population of acuña cactus containing 5.5 percent of known living acuña cacti occur in the Sand Tank Mountains. This area was designated for military purposes in 1941, and has had no livestock grazing for more than 60 years (Clinton 2001, p. 2). During a site visit in 2006, no habitat impacts from livestock were reported from this location (Anderson 2011, p. 2). The livestock management regime of no livestock being permitted within the Sonoran Desert National Monument Sand Tank Mountains acuña cactus population will be maintained for at least the next 15 to 20 years (BLM 2012c, p. 2-63; Foreman 2011, pers. comm.).

Mineral Mountain

—This population is discussed collectively below under “State Land”.

Federal Land—Department of Defense

Barry M. Goldwater Gunnery Range (BMGR)

—A single acuña cactus plant was found on BMGR approximately 1 km (0.62 m) to the north of a known population within the BLM Coffeepot ACEC (Geraghty

et al.

1997, p. 5). This individual was not relocated in a 2012 survey (Whittle 2012a, pers. comm.); however, this plant or its seedbank may remain. Livestock grazing is not authorized on the BMGR, though some trespass cattle do occur (Whittle 2012b, pers. comm.). Feral burros on BMGR are a concern, however, and BMGR managers plan to implement a burro trapping program in the future, in an attempt to reduce damage to vegetation (Whittle 2012b, pers. comm.).

State Land

Mineral Mountains

—Populations of acuña cactus on State land in the Mineral Mountains are subject to grazing; two land sections containing this species are collectively part of a larger 6,118 ha (15,118 ac) grazing lease with a total carrying capacity of 118 animal units (Sommers 2012, pers. comm.). Three individual acuña cacti from this group of populations overlap onto adjacent BLM land. This BLM land, which is not fenced from adjacent State land, has a total permitted number of cattle of 1,224, though the lessee did not run the full amount of animals in the past few years due to drought conditions (Tersey 2013, pers. comm.). During a 2011 site visit, the habitat appeared unaltered by livestock, and no cattle were seen (Service 2011b, p. 1).

Ninety-Six Hills

—Three additional land sections near Box O Wash containing this species are collectively part of a lease of 12,369 ha (30,565 ac) with a total carrying capacity of 236 animal units (Sommers 2012, pers. comm.). Both leases incorporate State and BLM lands, although in this area the species has been found on State lands and not the associated BLM lands. No livestock were seen during the November 2011 site visit to this population (Service 2011b, p. 3). Only 2 dead individual acuña cacti were found, and neither appeared to have been knocked over by cattle (Service 2011b, p. 3). In the past, Rutman and Krausman (1988, p. 1) recommended that this State land habitat could benefit from improved livestock management, as cattle trails there were numerous during a 1988 site visit. In a 2008 site visit, it was noted that quite a few of the dead acuña cactus plants may have been knocked over by livestock (Service 2008b, p. 1). It is unknown what the grazing lease or animal units were for this period of time. In 2011, several individuals were noted to have grown additional arms following the loss of the growing tip (Service 2011b, pp. 3-4). This was possibly due to injury caused by cattle, a beneficial adaptation to

disturbance noted previously by Phillips

et al.

(1982, p. 6). The populations on State land represent 2.1 percent of known living acuña cactus individuals. Although livestock grazing on State lands may benefit from improved management, the impacts to the acuña cacti are small.

Private Land

Ajo

—Populations of the acuña cactus on private lands near the town of Ajo were noted to occur in degraded habitat with low species richness; these sites were suspected to have had a grazing history of severe use (Rutman 1995, p. 1).

Florence

—Those acuña cacti on private lands near Florence are in an unknown condition, as they are not typically visited by Service staff. Two roadside populations visited in 2011 had 4 dead plants and 13 healthy plants collectively; all dead plants seemed to have died from drought or insect attack, although 1 population did contain evidence (feces) of cattle use (Service 2011b, p. 2). Private lands account for 2.2 percent of known living acuña cactus individuals.

Sonora, Mexico

In Mexico, researchers report livestock grazing in parts of the Sonora range (Stoleson

et al.

2005, p. 60), but mostly the habitat remains little-used and unoccupied land (Pate 2011, pers. comm.). Sonora maintains 28.5 percent of the known acuña cactus individuals across the range; their recent decline, as evidenced by 1,743 dead plants counted since 2010, has not been attributed to livestock.

In summary, 61 percent of acuña cactus individuals occur within lands protected from cattle grazing either by NPS or BLM National Monument status. In areas occupied by the acuña cactus where livestock grazing does occur, impacts from livestock do not appear to be a consistent or significant threat to populations. Based on our review of the available information, we conclude that, although there is evidence that grazing impacts to the acuña cactus do occur, we do not believe that these effects occur to such an extent that livestock grazing is a threat to the acuña cactus and its habitat.

Border Activities

Over the past decade or more, tens of thousands of people illegally attempt crossings of the U.S.-Mexico border into Arizona annually (cross-border violators) (Service 2011c, p. 14). As a result of increased U.S. Customs and Border Protection (CBP) activity in the Douglas, Arizona, area, and in San Diego and southeastern California, cross-border violator traffic has shifted into remote desert areas such as OPCNM (Service 2011c, p. 14). For example, in 2001, an estimated 150,000 people entered OPCNM illegally from Mexico (Service 2011c, p. 14). With the increase in technology, border fencing, and manpower between 2001 and 2012, these numbers are down considerably, with 6,218 arrests of cross-border violators from OPCNM in the year 2011 (Oliver 2012, pers. comm.). Although the number of arrests does not represent all those who attempted to enter OPCNM illegally, this number is suspected to be considerably less than reported in 2001. Despite the fact that these numbers are down due to enforcement and deterrence efforts by the CBP, the thousands of people crossing through the border area illegally still represent a substantial impact to the landscape.

More than 84 percent of the known living acuña cactus individuals occur within 16.5 km (10.25 mi) of the border in either OPCNM or Sonora, Mexico. Cross-border violators, CBP, and NPS law enforcement activity in this area may degrade acuña cactus habitat by creating new roads and trails, disturbing vegetation and soils, and moving exotic plant seeds or plant parts, leading to their spread into unoccupied areas (Duncan

et al.

2010, p. 124). At OPCNM, the acuña cactus occurs in an area that is closed to visitors due to dangers of drug and human smuggling. Significant impacts may occur when travel moves off existing roads causing vegetation destruction, soil compaction (Duncan

et al.

2010 p. 125), and, potentially, direct mortality of the acuña cactus by running over individuals, although no direct impacts to acuña cactus have been observed. Staff at OPCNM note that, in 2010, two vehicle tracks and associated articles of clothing from cross-border violators were found within one of the six 20-by-50-m (66-by-164-ft) acuña cactus long-term monitoring plots (Holm 2012a, pers. comm.). Although no individual plants were reported to have been run over in this instance, the occurrence of the activity within this proximity to acuña cactus individuals supports our conclusion that impacts from cross-border violators and border enforcement may negatively impact the species and could be a threat.

The NPS constructed a vehicle barrier along the U.S.-Mexico border at OPCNM in 2006 (Morawe 2012, pers. comm.). After the construction of the vehicle barrier, the general consensus of the OPCNM staff was that cross-boundary vehicle traffic had been reduced by 90 to 95 percent (Morawe 2012, pers. comm.). In 2008, the Department of Homeland Security completed an 8.4-km (5.2-mi) stretch of pedestrian fence, approximately centered on the border town of Lukeville. Some cross-border traffic continues to occur, but the majority of the remaining cross-country traffic in OPCNM is due to law enforcement activities (Morawe 2012, pers. comm.).

The Biological Opinion for the Ajo Forward Operating Base Expansion reported personal observations by NPS and Service employees that the number of off-road tracks and new roads continues to increase (Service 2011c, p. 19). These new off-road tracks and roads are believed to be the result of CBP response by vehicle, horseback, and foot to cross-border violators, whom are travelling primarily on foot (Service 2011c, p. 19). By 2011, OPCNM personnel had mapped thousands of miles of unauthorized off-road impacts from cross-border violators, CBP, and law enforcement activities (Service 2011c, p. 18). Staff at OPCNM has been compiling data on off-road traffic and mapping unauthorized roads on OPCNM for a report. This report was not available to us by the time of writing the final rule. Although most of the unauthorized roads were created prior to construction of vehicle barriers and pedestrian fences along the U.S.-Mexico border, it is not known if the additional roads were created after the construction of the border fences. In 2011, NPS staff noted no new heavily utilized routes due to off-road travel by vehicles, but staff did state that single vehicles drive across habitat and individual acuña cactus plants may be driven over. There is no evidence that acuña cacti have been harmed, but damage to larger plants has been documented due to similar activity (Rutman 2011, pers. comm.). In cooperation with Service staff, CBP has begun efforts to educate Border Patrol agents on the locations and appearance of acuña cactus so that the areas that support the plant can be avoided to the maximum extent possible. A road atlas has been printed and distributed to CBP agents working in the area, though acuña cactus habitat is not indicated on this map (Morawe 2012, pers. comm.).

A system of sensors and communication towers is currently in place and is being expanded within the border region; this technology improves deterrence, detection, and apprehension of cross-border violators entering or attempting to enter the United States illegally (Service 2009, p. 5). It is expected that, with increased communication and sensor tower technology, the need for CBP agents to

patrol the area will be reduced, thus reducing circumstances requiring vehicles to drive off authorized roads (Service 2009, p. 16). CBP agents on foot or on horseback may conduct off-road pursuit of suspected cross-border violators at any time, including in areas designated or recommended as wilderness (Service 2009, p. 17). Where such motorized pursuits are necessary, CBP has committed to using the least intrusive or least damaging vehicle readily available, without compromising officer or agency safety.

No existing or proposed communication towers are near any acuña cactus populations within OPCNM; however, human traffic patterns have changed since the installation of towers in and near OPCNM. These towers have been effective at reducing foot traffic through acuña cactus habitat (Morawe 2012, pers. comm.). When communication and sensor towers and associated tactical infrastructure require maintenance and repair, the acuña cactus could be directly affected by repair and maintenance of this infrastructure if maintenance vehicles traveled off approved access routes. The CBP has committed to use only approved access routes for these maintenance activities, and OPCNM staff report that CBP has kept their agreement in this regard. Because towers are effective at helping CBP see illegal activity, however, enforcement-related off-road vehicle activity has increased (Morawe 2012, pers. comm.). When walking into an area to do fieldwork, including acuña cactus annual monitoring, OPCNM staff understand that their footprints into sensitive habitat may be tracked by CBP agents (Morawe 2012, pers. comm.). In addition, if these maintenance and repair activities occur in undisturbed areas in the habitat of listed plant species, a survey must be conducted and a sufficient buffer created to protect any plants found (HDR 2012, pp. 4-3).

Illegal drug and human smuggling also adversely affects the area of the Coffeepot ACEC, but the area is less impacted than other border areas (BLM 2011, p. 344). This is likely the case with the other populations on private and BLM lands near Ajo. Within BMGR, cross-border violators and associated activities represent a significant threat to natural and cultural resources within the BMGR, including having widespread and adverse effects on soil and hydrology (U.S. Departments of the Air Force and Navy 2007, pp. 3-11). We are aware of no instances of illegal activity or law enforcement activity impacting the populations near Florence. The Service (2008b, p. 1) noted that little to no human activity, including ORV use, was observed during a 2008 site visit to these populations.

The acuña cactus populations across the border from OPCNM, in Mexico, occur on land that is little used, unoccupied, and subject to heavy traffic by drug and human smugglers (Pate 2011, pers. comm.). This area was reported to be unsafe, and warnings were given to Service personnel not to travel to this location alone (Larios 2012, pers. comm.). In 1993, the Mexican Government established Pinacate Biosphere Reserve, a 7.7-million ha (1.9-million-ac) reserve for the region's flora, fauna, geology, and archeology preservation. A portion of the acuña cactus individuals in Sonora occur within the Pinacate Biosphere Reserve. It is unknown what, if any, protection this designation provides the acuña cactus.

In summary, the two areas containing the largest number of living acuña cactus (84 percent of the known living acuña cactus individuals) occur along the U.S.-Mexico border (in OPCNM and Sonora, Mexico). Within populations, acuña cacti are typically spaced within 3 m (9.8 ft) of each other, and vehicle traffic through any population could potentially impact many individuals. This area is heavily impacted by cross-border violators, CBP, and law enforcement activity, as evidenced by the tremendous increase in illegal roads and trails documented by agencies along the border. To date, no individual acuña cactus plants are reported to have been lost to these activities; however, reporting from this area is inconsistent. With anticipated continued border activity in the area, it remains possible that acuña cactus individuals and their habitat will be impacted. These impacts include: Creation of new roads and trails; disturbance of associated vegetation including nurse plants and microclimates; compaction or erosion of soils; movement of nonnative, invasive plant seeds and plant parts; and the potential to cause direct mortality to individuals by running over plants with vehicles. Therefore, based on our review of the available information, we conclude that cross-border violators, CBP, and law enforcement off-road activities are a threat to the acuña cactus and its habitat.

Nonnative, Invasive Plant Species

Throughout the Sonoran Desert ecosystem, invasions of the introduced

Pennisetum ciliare

(buffelgrass),

Bromus rubens

(red brome),

Eragrostis lehmanniana

(Lehmann lovegrass),

Schismus barbatus

(Mediterranean grass), and

Pennisetum setaceum

(fountaingrass) have altered nutrient regimes; species composition and structure through competition for open space; microclimates; and fire frequency, duration, intensity, and magnitude (Brooks and Pyke 2001, p. 5). Although most of these species were intentionally introduced as forage for livestock, as erosion control, or as ornamentals, each is now considered invasive and a threat to this ecosystem (Búrquez-Montijo

et al.

2002, entire). Species such as buffelgrass are expected to increase their range even with continued and predicted drought events (Ward

et al.

2006, p. 724). It is generally thought that invasion by exotic annual grasses will continue unchecked in the Sonoran Desert ecosystem in the future, reducing native biodiversity through direct competition and alteration of nutrient and disturbance regimes (Franklin and Molina-Freaner 2010, p. 1671).

Herbarium sheets contain labels that give information regarding where a specimen was collected, by whom, when the collection was made, and additional information such as what plant species were found in association with the collected specimen. There are no exotic species noted as associates on 39 of the 40 acuña cactus specimen herbarium sheets located at the Arizona State University, University of Arizona, or San Juan College Herbarium collections (ARIZ 2011, entire). These collections cover the range of the acuña cactus and date from 1952 through 2009. One specimen collected in 1982 has exotic annual red brome grass listed as an associate. Although fountaingrass found on nearby property was reported to be a possible threat to the acuña cactus near Ajo (Falk 2005, pers. comm.), no exotic grasses were noted within the Ajo, Little Ajo Mountains, or Coffeepot ACEC habitats during field surveys in October 2011 (Service 2011, p. 4). One researcher familiar with all known populations of the acuña cactus noted no associated threats from exotic plant species in any population (Baker 2011, pers. comm.). However, according to a peer-review comment received regarding this rule, buffelgrass is reported to be abundant and rapidly expanding in the Ajo region, the Sauceda Mountains, and the Sikort Chuapo Mountains, which lie between these two areas (Morawe 2012, pers. comm.). This reviewer also noted that buffelgrass is increasing distribution within ORCNM such that it now surrounds the entirety of acuña cactus habitat (Morawe 2012, pers. comm.).

Two of our peer reviewers feel that, although no acuña cactus populations are currently known to harbor buffelgrass, given the current rate of expansion and lack of management programs in many areas, buffelgrass could appear in acuña cactus populations within 5 to 20 years.

In summary, we have reviewed the available information on the effects of and occurrence of nonnative, invasive plants in or near populations of the acuña cactus in southern Arizona and Sonora, Mexico. Known populations of the acuña cactus are well distributed across southern Arizona and northern Sonora and occur in areas subject to effects from nonnative, invasive plant species. Although no populations of the acuña cactus currently show evidence of effects from nonnative, invasive species, reports indicate that buffelgrass is currently in close proximity and could expand into acuña populations within the near future. Therefore, our review of the best scientific and commercial data available indicates that, while nonnative species do not co-occur with the acuña cactus presently, there is potential for the invasion of at least one troublesome invasive plant, buffelgrass, within the near future. Therefore, we conclude nonnative, invasive species pose a threat to the acuña cactus and its habitat.

Mining

The immediate threats from mining activity include the direct loss of individuals and habitat. Indirect impacts of mining activity include fragmentation of acuña cactus and associated pollinator populations, which can reduce genetic vigor of the cactus and result in degradation and fragmentation of habitat and dusting of individual cacti adjacent to mines and associated roads.

The acuña cactus populations in OPCNM and the Sonoran Desert National Monument are protected from the immediate threats associated with mining due to their National Monument status (NPS 1997, pp. s-iii; BLM 2012c, p. 2-69). The 2012 BLM Sonoran Desert National Monument RMP continues the mining closure within the boundaries of the National Monument (BLM 2012c, p. 2-69). Authorized surface-disturbing activities within occupied acuña cactus habitat areas within the Coffeepot ACEC will be minimized, mitigated, or avoided to ensure stable populations (BLM 2012b, p. 2-32). The ACEC is closed to saleable minerals (e.g., sand and gravel; BLM 2012b, p. 2-88, Map 14), open with special mitigation to leasable minerals (e.g., oil and gas; BLM 2012b, p. 2-88, Map 13), and open, subject to mitigation to maintain resource values, for locatable minerals (hard rock mining; BLM 2012b, p. 2-87). No known mining activities are planned on BLM properties, though a BLM parcel adjacent to populations on State lands near Florence may host a gravel mining operation in the future (Service 2011b, p. 1). Verified mining threats near Florence, as well as within Mexico, are unknown.

Mining activity on private land near Ajo has a long history; the New Cornelia copper mine was one of the first open pit mines in Arizona dating to 1854 (Arizona Mining Association 2011, entire). This mine was closed in 1985, and a 2008 investigation by company owners determined the mine would not be reopened due to current economic conditions (Ajo Copper News Oct 29, 2008). As of 2013, the mine remains closed.

The small populations of the acuña cactus that remain in Ajo may have been part of a much larger population that occurred before mining activity began, but there are no survey records for this species in the area prior to mining activity. As a result, it is unclear to what extent the acuña cactus and associated habitat were removed due to historical mining in this area, but there was certainly some loss of individual acuña cactus and habitat. Rutman (1995, p. 1) noted that on the east side of the Ajo rock dump, roads, wells, prospecting holes, rock piles marking mining claims, and past use of explosives occurred immediately adjacent to the acuña cactus plants. Rutman (2006, p. 1) noted that habitat was lost when Indian Hill Village Road was built and occupied habitat may also have been lost where the following buildings and infrastructure now occur: Assembly of God Indian Mission, New Cornelia mine, parking lot for the mine lookout, baseball diamond, and the large informal parking lot to the north of the hill. It is possible that these populations were at one time connected with the few plants to the southeast of the open pit mine on BLM land. There is little doubt that the historical size and range of the Ajo area populations of acuña cactus have been reduced.

We are aware of no acuña cactus populations that are currently impacted by active mining. It is reasonable to project that some mining will occur in the future that could affect acuña cactus populations near Florence, Ajo, and in the Coffeepot ACEC. However, these effects will occur in limited areas that do not support a majority of known individual acuña cactus. The acuña cactus populations will remain well distributed across their range even if future mining activities affect a few populations. Therefore, based on our review of the available information, we conclude that current mining activity and mining in the near future are not threats to the acuña cactus and its habitat.

Drought and Climate Change

Our analyses under the Act include consideration of ongoing and projected changes in climate. The terms “climate” and “climate change” are defined by the Intergovernmental Panel on Climate Change (IPCC). “Climate” refers to the mean and variability of different types of weather conditions over time, with 30 years being a typical period for such measurements, although shorter or longer periods also may be used (IPCC 2007, p. 78). Thus, the term “climate change” refers to a change in the mean or variability of one or more measures of climate (e.g., temperature or precipitation) that persists for an extended period, typically decades or longer, whether the change is due to natural variability, human activity, or both (IPCC 2007, p. 78). Various types of changes in climate can have direct or indirect effects on species. These effects may be positive, neutral, or negative, and they may change over time, depending on the species and other relevant considerations, such as the effects of interactions of climate with other variables (e.g., habitat fragmentation) (IPCC 2007, pp. 8-14, 18-19). In our analyses, we use our expert judgment to weigh relevant information, including uncertainty, in our consideration of various aspects of climate change.

Climate change will be a particular challenge for biodiversity because the interaction of additional stressors associated with climate change and current stressors may push species beyond their ability to survive (Lovejoy 2005, pp. 325-326). The synergistic implications of climate change and habitat fragmentation are the most threatening facet of climate change for biodiversity (Hannah

et al.

2005, p. 4). Current climate change predictions for terrestrial areas in the Northern Hemisphere indicate warmer air temperatures, more intense precipitation events, and increased summer continental drying (Field

et al.

1999, pp. 1-3; Hayhoe

et al.

2004, p. 12422; Cayan

et al.

2005, p. 6; Seager

et al.

2007, p. 1181). Climate change may lead to increased frequency and duration of severe storms and droughts (Golladay

et al.

2004, p. 504; McLaughlin

et al.

2002, pp. 6072-6074; Cook

et al.

2004, p. 1015).

The current prognosis for climate change impacts in the American Southwest includes fewer frost days; warmer temperatures; greater water demand by plants, animals, and people; and an increased frequency of extreme weather events (heat waves, droughts, and floods) (Weiss and Overpeck 2005, p. 2074; Archer and Predick 2008, p. 24). How climate change will affect summer precipitation is less certain because precipitation predictions are based on continental-scale general circulation models that do not yet account for land use and land cover effects or regional phenomena, such as those that control monsoonal rainfall in the Southwest (Weiss and Overpeck 2005, p. 2075; Archer and Predick 2008, pp. 23-24). Some models predict dramatic changes in southwestern vegetation communities as a result of climate change (Weiss and Overpeck 2005, p. 2074; Archer and Predick 2008, p. 24), especially as wildfires carried by nonnative plants (e.g., buffelgrass) potentially become more frequent, promoting the presence of invasive, exotic species over native ones (Weiss and Overpeck 2005, p. 2075). The Sonoran Desert has experienced drought conditions since 1998 (Bowers 2005, p. 421; Western Region Climate Center (WRCC) 2012, entire). Recent trends for the region predict that climate of the region will become much drier in the next 2 to 3 decades (Schwinning

et al.

2008, pp. 14-15). The impact of current and future drought, which may be long-term and severe (Seager

et al.

2007, pp. 1183-1184; Archer and Predick 2008, entire), will continue to affect the acuña cactus and its habitat throughout its range.

Climate change is likely to affect the long-term survival and distribution of native plant species, such as the acuña cactus, through changes in temperature and precipitation. Over the past 40 to 50 years, the United States has experienced more extreme weather events, heat waves, and regional droughts than in previous decades (Karl

et al.

2009, p. 27). The southwestern United States has experienced the greatest temperature increase in the continental United States; average temperatures increased approximately 0.8 degrees Celsius (°C) (1.5 degrees Fahrenheit (°F)) compared to a 1960 to 1979 baseline (Karl

et al.

2009, p. 129). By the end of this century, temperatures averaged across the Southwest region are expected to warm a total of 2 to 5 °C (4 to 10 °F) above the historic baseline period of 1960-1979 (Karl

et al.

2009, p. 129). The frequency and intensity of high temperature extremes will increase, and heat waves currently considered rare will become more common (Karl

et al.

2009, pp. 33-34). This region has experienced drought conditions since 1998 (Bowers 2005, p. 421; WRCC 2012, entire). Annual mean precipitation levels are expected to decrease in western North America and especially the southwestern States by midcentury (IPCC 2007, p. 8; Seager

et al.

2007, p. 1181; Girvetz

et al.

2009, entire). The current trend in the Southwest of less frequent, but more intense, precipitation events leading to overall drier conditions is predicted to continue (Karl

et al.

2009, p. 24). The levels of aridity of recent drought conditions and perhaps those of the 1950s drought years will become the new climatology for the southwestern United States (Seager

et al.

2007, p. 1181). In summary, the drought the southwestern United States has been experiencing since the late 1990s is the worst in more than 100 years and is being exacerbated by record warming (Karl

et al.

2009, p. 130).

Heat stress in adult cacti is minimal compared to other plant species as they are able to survive heat stress due to both morphology and metabolism (Smith

et al.

1984, pp. 647, 650; Wahid

et al.

2007, p. 199). In a study of Sonoran Desert cacti, Smith

et al.

(1984, pp. 647, 650) found that short cacti (such as the acuña cactus) and massive cacti had higher heat tolerance than most other cacti species studied, and more than vascular plants overall. They also found heat tolerance varied with stem orientation, stem diameter, and location on the landscape including a portion of the species' range (Smith

et al.

1984, p. 649). Extreme temperatures can, however, negatively impact seedling survival in many Sonoran Desert plants, and drought coupled with high temperatures lessens temperature tolerance in seedlings (Nobel 1984, pp. 310, 316). We found no additional information on projections for cacti in general, or the acuña cactus in particular, indicating the impacts of increased heat stress combined with increasing drought stress as climate models project. We do know, however, that drought or high temperatures alone can damage non-cacti species, and the combination causes more detrimental interactive effects on these plants than either stressor independently (Huang and Jiang 2002, p. 288).

We are aware of several reports of drought stress apparent on individual acuña cactus. In cacti and other succulents, stem swelling and shrinking is typical with rain-drought cycles (Mauseth 2000, p. 1107). At OPCNM, monitored acuña cactus individuals were reported to have shrunk in size from 1 year to the next, and researchers noted shrinking individuals may be dying (Ruffner 1989, p. 1). In addition, 1986 datasheets from monitoring plots at OPCNM categorized cacti based on health of the individual; one category from the time was “desiccated” (dried out) (Buskirk 1986, pers. comm.). Although such descriptive categories have not been in use in monitoring for some time, OPCNM staff note their importance and would like to reinstate them in future monitoring (Holm 2012b, pers. comm.). In addition, plants already stressed from prolonged drought are more susceptible to insect attack and disease (Mattson and Haack 1987, p. 110), and such attack is prevalent in all acuña cactus populations across their range (see discussion in

Factor C. Disease or Predation

). Mortality in measured plots at OPCNM was most severe in 1993, when 40 adults were lost, and again in 1997, when 53 adults were lost (NPS 2011a, p. 2); both of these were years with dry summers (WRCC 2012, entire). Between 2001 and 2011, 78 adults were lost in these plots, and 25 of these losses occurred in the very dry year of 2007 (NPS 2011a, p. 2; WRCC 2012, entire). During this same 10-year period, 31 new adults were recorded as additions to the population through recruitment (NPS 2011a, p. 2).

In addition to the health of adult individuals, drought is directly related to acuña cactus population health with regard to reproduction and establishment. In his 3-year study of the reproductive ecology of the acuña cactus, Johnson (1992, pp. 403, 405) concluded that the positive association of rainfall and annual variation in the number of flowers produced indicates that water availability limits flower production in this species. Although Johnson cites yearly precipitation in relation to flower production, it seems more likely that winter precipitation is the driving factor, as flowers are produced early in the spring following winter precipitation events. Within monitoring plots established by Buskirk in 1977 (Buskirk 1981, p. 1), total flowers counted peaked at 902 in 1992 (Holm 2006, p. 10); corresponding precipitation during the winter of 1992-1993 was 29.7 cm (11.66 in) (WRCC 2012, entire). By comparison, in the last 10 years of measurement, the average number of flowers counted in these plots was 198 (Holm 2006, p. 10); the corresponding average winter precipitation during these years was 9.7 cm (3.8 in) (WRCC 2012, entire).

Resource limitation may affect the acuña cactus seed set through ovule abortion (Johnson 1989, p. 11). Because

flowering commences in early March and fruiting commences in late April (Johnson 1989, pp. 5, 8), it is likely also that winter precipitation is correlated with fruit set. Fruit production was monitored at the OPCNM plots beginning in 2004, and has shown considerable variation since that time with a low of 29 fruits produced in 2007, when total winter precipitation was 6.8 cm (2.69 in), and a high of 361 fruits produced in 2005, when winter precipitation was 16.4 cm (6.47 in) (NPS 2011a, p. 1; WRCC 2012, entire).

Johnson (1989, pp. 5, 12) determined that acuña cactus seedling survival was dependent on summer precipitation and that soil moisture availability limits the distribution of the species. Rice (2001, pers. comm.) noted that in greenhouse trials of the acuña cactus, seedlings and new recruits were primarily lost due to desiccation; emphasizing that establishment is the most critical and limiting phase of the acuña cactus life cycle. Throughout the species' range, rainfall has been declining, and drought conditions have been dominant since 1998 (Bowers 2005, p. 421; WRCC 2012, entire); this has likely influenced seedling survivorship (Holm 2006, p. 2-1—2-13; NPS 2011a, p. 1). For example, in the measured plots at OPCNM, the recruitment rate peaked in 1992, coinciding with consecutive seasons with near to above average rainfall (NPS 2011a, p. 1; WRCC 2012, entire). In the Coffeepot Mountain BLM monitoring plots, seedling or juvenile plants were observed in all years when plots were measured; however, the number of dead plants far exceeded recruitment in any year (Butterwick 1982-1992, entire). In many site visits throughout the region over the past 10 years, there have been reports of low or no recruitment (Service 2008a, p. 1; Service 2008c, p. 1; Anderson, 2011, p. 2; Service 2011a, entire; Service 2011b, p. 3; Westland Resources 2013, p. 4).

In summary, since the late 1990s, the southwestern United States has been experiencing drought conditions and increasing high temperatures. Climatic predictions suggest continued less frequent, but perhaps more intense, summer precipitation, reduced winter precipitation; and increasing temperatures in this region (Seager

et al.

2007, p. 1181; Archer and Predick 2008, pp. 23-24; Karl

et al.

2009, p. 24). Data from the acuña cactus monitoring plots at OPCNM and at Coffeepot Mountain, along with occasional surveys of these and most other populations, indicate major population declines have occurred across the acuña cactus range over the past 30 years. It appears that a combination of drought stress, warmer winters, and insect attack have reduced adult plant numbers, while heat stress, lack of precipitation, and seed predation have combined to reduce or halt reproduction (see

Factor C. Disease or Predation,

below). Because the current drought is occurring on a regional scale, and because climatic models predict future regional droughts, it is likely that all populations of the acuña cactus will continue to decline due to drought and the effects of climate change. In addition, it appears that drought and climate change in combination with insect damage and predation, as a combined effect, is the more likely scenario for rangewide level impacts to acuña cacti (see

Factor C. Disease or Predation,

below). Most, if not all, of the acuña cactus populations are impacted by drought and the effects of climate change, including effects to both individual cacti and to productivity and establishment. Therefore, based on our review of the best scientific and commercial data available, we conclude that drought and the effects of climate change are threats to the acuña cactus across its range. When combined with insect predation (see

Factor C. Disease or Predation,

below), the effects on acuña cactus populations are significant.

Summary of Factor A

In conclusion, based on our review of the best scientific and commercial data available, we have determined that individual plant loss, as well as fragmentation of acuña cactus and associated pollinator populations due to the effects of urbanization; livestock grazing; and mining do not impact the species at a population level and, therefore, are not threats to the acuña cactus. Currently, 84 percent of the known living acuña cactus individuals occur along the border near OPCNM. Cross-border violators and associated CBP and law enforcement off-road activities may be affecting individual acuña cactus plants and their habitat. If there is an increase in off-road activities in or near acuña cactus populations or habitat, the likelihood of loss of individuals or loss or modification of habitat also increases. In addition, while no populations of the acuña cactus currently show evidence of effects from nonnative, invasive species, reports indicate that buffelgrass is currently in close proximity and could expand into acuña populations within the near future. Finally, a large amount of mortality has been documented within all populations that have been visited more than once, relating to a combination of the intricately correlated increases in drought and heat stress, warmer winter temperatures, and insect attack (see

Factor C. Disease or Predation,

below). Thus, based on our review of the best scientific and commercial data available, we conclude that loss and degradation of habitat due to nonnative, invasive species; off-road border activities; and the effects of drought and climate change, are threats to the acuña cactus and its habitat.

Factor B. Overutilization for Commercial, Recreational, Scientific, or Educational Purposes

Unauthorized collection has, in the past, been identified as a threat to the acuña cactus (Phillips

et al.

1982, p. 9; Phillips and Buskirk 1982, p. 2; Rutman 1996a, pers. comm.; Rutman 2007, p. 6). At OPCNM, a large number of individuals are located adjacent to Puerto Blanco Drive, which was formerly a scenic loop drive. Although historically collection is suspected to have occurred in this population (Buskirk and Phillips 1983, pers. comm.; Rutman 1996a, pers. comm.), the significance of this past collection varies. Buskirk (1981, p. 5) noted that he did not believe collection was a significant source of mortality between 1977 and 1981, yet Phillips and Buskirk (1982, p. 2) noted three mapped roadside cacti lost to collectors, stating that collecting could be a significant cause of loss in OPCNM. Additionally, Rutman (1996a, p. 2) noted that along the scenic drive road at OPCNM, considerable collection of the largest size class of plants occurred. This road was closed to visitors in 2003; the staff of OPCNM hope to reopen this road in the future, though it will remain closed indefinitely while border issues continue, making it unlikely that collection will occur there in the near future (Rutman 2011, pers. comm.; Morawe 2012, pers. comm.; Pate 2012a, pers. comm.).

On BLM-administered lands, the acuña cactus plants occur in very remote locations, and no reports of collection are known. Rutman (1995, p. 2) noted collection did not appear to be a threat to the population surrounding the Coffeepot Mountain plots during annual visits between 1988 and 1990. Similarly, no evidence of collection was seen during 2011 Service and BLM site visits to nearby populations within the Coffeepot ACEC (Service 2011a, p. 4).

On State and private lands in the Florence area, Rutman (1995, p. 3) noted that population locations were published and, easy to access, and that, for many years, collectors have been taking plants. She also noted individual plants seen the previous year were missing, and no carcasses were found

upon revisiting (Rutman 1995, p. 3). No evidence of collection from visited sites was found during 2011 Service visits (Service 2011b, p. 1). Private lands in the Ajo area are also accessible, though we have no reports of collection there.

Buskirk and Phillips (1983, pers. comm.) refer to some acuña cactus collection, but refer to it as relatively uncommon and unsystematic at present. No documented cases of unauthorized collection (in violation of the Arizona Native Plant Law) of this cactus have been found in any of the known populations. Heil and Melton (1994, p. 15) note that the acuña cactus is easy to grow and raise from seed and that this species is rare in the gardens of cactus collectors. An investigator within the Office of Special Investigations of the Arizona Department of Agriculture stated that he does not believe collection of the acuña cactus is a threat to the species (Reimer 2011, pers. comm.). Therefore, based on our review of the best scientific and commercial data available, we conclude that, while there is evidence that unauthorized collection of the acuña cactus did occur in the past, there is little evidence that collection occurs to such an extent currently as to constitute a threat to the acuña cactus, nor do we expect collection to become a threat in the future.

Factor C. Disease or Predation

In general, cacti are susceptible to attacks from numerous types of insects, and the acuña cactus is no exception. The interior flesh of cacti provides both a nesting area and food source for beetles, weevils, and other insects. Once an infestation has occurred, cacti can die from the eating and tunneling activities or from the introduction of fungus or disease. In addition, drought may cause physiological stress responses in plants, such as limiting their photosynthesis and cell growth. Plants already stressed from prolonged drought are more susceptible to insect attack and disease (Mattson and Haack 1987, p. 110).

Four native species of insects have been documented to impact the acuña cactus. Of these, cactus weevils (

Gerstaeckeria

spp.) and cactus longhorn beetle (

Moneilema gigas

) are documented to be most responsible for the acuña cactus declines (Rutman 2007, p. 6; Johnson 1989, p. 10). Cactus weevils are stem-boring insects; the adults feed externally while the larvae feed internally (Burger and Louda 1995, p. 1560). Cactus longhorn beetle adults feed on pads or terminal buds of cacti; their larvae burrow into stems or roots causing the severing of root and stem, collapse, and death of plants (Kelly and Olsen 2011, p. 7; Johnson 1989, p. 10). Raske 1966 (p. 106) cites Dodd (1927) stating that the cactus longhorn beetle has one reproductive cycle per year; however, a noted cactus expert, Alan Zimmerman, believes that increased warming in recent decades facilitates longer breeding cycles and more reproduction in both the cactus longhorn beetle and cactus weevil (Rutman 2007, p. 6).

Other insects with lesser impact on the acuña cactus are snout moth (

Yosemitia graciella

) larvae and unknown ant species. Snout moth larvae are noted to feed internally on cacti (Simonsen and Brown 2009, entire) and on fruits, thus reducing seed set (Johnson 1992, p. 405). Johnson (1992, p. 405) noted snout moth predation accounted for a reduction in seed set of 35 percent in 50 monitored plants at OPCNM. Ants have been noted in greenhouse conditions and in the wild to consume and transport the acuña cactus seeds (Butterwick 1982-1992, entire; Rutman 1996b, pers. comm.; Rutman 2001, pers. comm., p. 1; Anderson 2011, p. 1). In a similar species,

Coryphantha robustispina

ssp.

robustispina

(Pima pineapple cactus), ants have been documented eating fruits and transporting seeds (Baker 2011, pp. ii, 23). While ants do consume seed, they also scatter seed away from the mother plant thereby reducing predation by small mammals (O'Dowd and Hay 1980, p. 536; Vander Wall

et al.

2005, p. 802). Ants may also aid in reducing the seedbank of competing plant species (O'Dowd and Hay 1980, p. 539). All of the above-mentioned insects have been documented at OPCNM near or on acuña cactus individuals (Johnson 1989, p. 10; Johnson 1992, p. 405; Rutman 1996b, pers. comm.; Rutman 2001, pers. comm., p. 1), with ants documented at Coffeepot Mountain (Butterwick 1982-1992, entire). It is likely that insect depredation occurs in other populations as well, though studies have not been conducted, and insects have not been collected in these populations. No diseases have been documented in the acuña cactus, though plants are exceptionally susceptible to bacterial rot after minor stem damage (Rutman 2007, p. 3). In 2011 site visits across the species' range, a majority of living adult acuña cacti were in various stages of decline, with stems blackening from the base upward and resulting in eventual cactus death. The cause of this blackening is unknown; it could be natural aging of the plants or the result of stress, insect damage, or disease.

A variety of small mammals, such as native ground squirrels, pack rats, rabbits, and mice, can severely damage or kill both mature and young cacti during times of drought when free water is unavailable (Kelly and Olsen 2011, pp. 8-9). There have been reports of loss of the acuña cactus due to small mammal depredation evidenced by scattered spines and rooted bases at OPCNM (Buskirk 1981, p. 5; Buskirk and Phillips 1983, pers. comm.; Heil and Melton 1994, p. 15; Holm 2006, pp. 2-3). In general, plants that die of desiccation, insect damage, or disease leave erect carcasses, while those that die from small mammals leave only scattered remains of the cacti in the vicinity (Morawe 2012, pers. comm.). It is likely that small mammal depredation occurs in other populations outside of OPCNM as well, though studies have not been conducted and small mammal occurrence in these populations has not been documented.

In 2011, nearly all populations of the acuña cactus on BLM, State, and some private lands were visited by Service staff (Service 2011a, entire; Service 2011b, entire). In every population, some partially living and dead plants were found uprooted and toppled over. This was also noted in 2013 in a population near Ajo on BLM land (Westland Resources 2013, p. 3). In 1996, there was a high mortality event associated with many live, reproductive plants found uprooted and lying on the ground in the Coffeepot Mountain population and the populations around Ajo (Rutman 2007, p. 3). This episode has not been explained; however, various hypotheses include vandalism, thrashers (birds) digging them up, and javelinas uprooting the plants. Given the severing of stem from root that commences when plants are infested with cactus longhorn beetle, it is entirely possible that episodes of plants falling over occur following peak years for these insects, possibly in association with birds or other animals hearing and attempting to remove the insects within. There were above-average temperatures in Ajo the 2 years preceding the 1996 uprooting event; this uprooting may have been correlated to increased insect activity and uprooting. Above-average annual temperatures have been recorded at the Ajo Weather Station 15 times during 25 years of recordkeeping between 1975 and 2010 (WRCC 2012, entire). This trend is consistent both at OPCNM and in Florence, where 21 of 25 recent years and 19 of 25 recent years, respectively, had above-average temperatures (WRCC 2012, entire). The increased warming in recent decades is likely benefiting insects and stressing acuña cactus plants, resulting in

significantly increased mortality rangewide.

Between 1982 and 1992, both recruitment and mortality were recorded within and outside of the established BLM plots at the Coffeepot Mountain acuña cactus population. Field notes from throughout the 10-year period of study indicate insect damage to individual plants has been ongoing within this population. Field notes included the following comments: tubercles (knoblike projections on the main stem) with holes, damage on apex (top), exposed root, numerous ants, plant dying, insect damage to fruit, hollow inside, uprooted, chlorotic (yellowing), beetle wounds on side, unhealthy, damaged meristem (growing tip), appears dying at the base, base rotting, sickly, and not rooted (Butterwick 1982-1992, entire). In 1987, the BLM reported high mortality in this population with more dead plants observed (332) than living (310) (Rutman

et al.

1987, p. 1). In 1989, the BLM reported a precipitous decline of this population (Johnson 1989, p. 18). In 2008, staff of OPCNM censused this population and found 77 living and 80 dead plants (Morawe 2012, pers. comm.) with low or no recruitment reported from the entire population during 21 site visits between 1992 and 2011 (Anderson 2011, entire). Within the monitoring plots at OPCNM, datasheets from 1986 categorized cacti as being: uprooted from the base, shell of spines, dead with upright carcass, stepped on, and missing, among others (Buskirk 1986, pers. comm.). Within these plots, adult recruitment has been observed in every year of monitoring since 1989; mortality has been observed in all but 2 years during this same period (NPS 2011a, p. 1). On average, the annual adult mortality within these plots is 12 percent, exceeding the annual recruitment of 7.7 percent (NPS 2011a, p. 1). The decrease in reproduction, increase in mortality, or a combination of both have resulted in the decline in plants within (NPS 2011a, p. 1) and outside of the plots at OPCNM. Across this population, the previous estimate of acuña cactus numbers were greater than 10,000 individuals (Buskirk 1981, p. 3); current estimates are between 1,000 and 2,000 plants total (Rutman 2011, pers. comm.).

At Coffeepot Mountain, population decline has been dramatic with at least two episodes of 50 percent reductions reported from individuals in and around monitoring plots (Butterwick 1982-1992, entire; Rutman

et al.

1987, p. 2; Anderson 2011, p. 2; Anderson 2012b, pers. comm.; Morawe 2012, pers. comm.). At OPCNM, the number of individuals on all 6 monitoring plots has declined in all but 2 years since 1989 (NPS 2011a, p. 1; NPS 2012, p. 2), and in total population estimates between 1981 and 2011 (Buskirk 1981, p. 3; Rutman 2011, pers. comm.). In 2011, site visits to most of the remaining populations on BLM, State, and private lands indicated large proportions of the populations were dead with many plants uprooted, hollow plants, and many individuals in all size classes reported to be unhealthy or blackening from the base (Service 2011a, entire; Service 2011b, entire). Also, researchers in Mexico reported that 62.9 percent of the 2,773 total plants found were dead (Pate 2012b, pers. comm.; Van Devender 2013, pers. comm.).

In conclusion, uprooting and depredation have been ongoing for at least several decades at OPCNM, at Coffeepot Mountain, and in other populations. The pronounced decline in the acuña cactus numbers over the last 3 decades documented throughout the species' range on BLM, State, and private lands, as well as lands in Sonora, Mexico, is of serious concern. It appears that the combination of drought stress and insect attack have reduced adult plant numbers and that warmer winters may be increasing insect numbers attacking acuña cacti. Most, if not all, of the populations are significantly impacted by predation; predation, in the form of insect attacks, occurs throughout the range of the acuña cactus. We also believe that the extent to which this threat affects the acuña cactus populations is interactive with the occurrence of drought and other climatic variables such as warmer winters. The ability of the acuña cactus populations to recover from insect attacks depends on the successful germination and survival of seedlings. However, these populations are also experiencing decreased reproduction, which may render the populations unable to recover as they continue to lose mature individuals, with low levels of seedling recruitment and survival. Therefore, based on our review of the best scientific and commercial data available, we conclude that predation is a threat that is resulting in significant population impacts to the acuña cactus, and this threat is expected to continue into the future.

Factor D. The Inadequacy of Existing Regulatory Mechanisms

Under this factor, we examine whether existing regulatory mechanisms are inadequate to address the threats to the species discussed under the other factors. Section 4(b)(1)(A) of the Act requires the Service to take into account “those efforts, if any, being made by any State or foreign nation, or any political subdivision of a State or foreign nation, to protect such species. . . .” We interpret this language to require the Service to consider relevant Federal, State, and tribal laws, plans, regulations, cooperative agreements, and other such mechanisms that may minimize any of the threats we describe in threat analyses under the other four factors, or otherwise enhance conservation of the species. We give strongest weight to statutes and their implementing regulations and management direction that stems from those laws and regulations. An example would be State governmental actions enforced under a State statute or constitution, or Federal action under statute.

Having evaluated the significance of the threat as mitigated by any such conservation efforts, we analyze under Factor D the extent to which existing regulatory mechanisms are inadequate to address the specific threats to the species. Regulatory mechanisms, if they exist, may reduce or eliminate the impacts from one or more identified threats. In this section, we review existing State and Federal regulatory mechanisms to determine whether they effectively reduce or remove threats to the acuña cactus.

Regarding the threat of unauthorized collection, the acuña cactus is protected by the Arizona Native Plant Law (Arizona Revised Statutes, Chapter 7, 2007, entire), which prohibits collection without obtaining a permit on all public lands and directs that plants may not be moved off private property without contacting the Arizona Department of Agriculture. Due to the difficulty in implementing this law, it has not been effective in reducing impacts from collection, nor does it protect habitat. However, no documented cases of unauthorized collection of this cactus have been found in any of the known populations in recent decades. There is little threat of collection on private lands due to restricted public access (see

Factor B. Overutilization for Commercial, Recreational, Scientific, or Educational Purposes

); the majority of the acuña cactus populations are on State and Federal lands. In addition, NPS regulations prohibit the collection or removal of the acuña cactus on NPS lands, where the largest known acuña cactus population occurs. The main road accessing the acuña cactus population in Acuña Valley in OPCNM is currently closed to the public, thus reducing impacts from collection to this population. Although the remoteness of many populations limits both visitation and enforcement of the existing

regulatory mechanisms, unauthorized collection is reported to result in a relatively minor impact to this species. We conclude that the regulations that exist to protect against the impacts from over collection of the species, primarily the NPS regulation prohibiting removal and the closure of the primary access route in OPCNM, are serving to reduce the impacts from collection.

No regulations in place address threats to acuña cactus and its habitat from site degradation or address the primary threats to acuña cactus of insect predation, drought, and the effects of climate change. Urban development, livestock grazing, unauthorized collection, and mining are not identified to occur at a level that is a threat to acuña cactus populations. However, without management of impacts from these activities, impacts could rise significantly. Special management prescriptions in place address some of these concerns on Federal lands. For example, the Sonoran Desert National Monument and OPCNM exclude livestock grazing and mining, promote the reduction of nonnative, invasive plant species, and are unlikely to support urban development. In Mexico, a portion of the known population is within the boundary of Pinacate Biosphere Reserve, which may afford some protections. While management prescriptions with regard to these stressors may be applied opportunistically across different land management agencies within the region, they do afford some protection and minimize impacts to the species and its habitat.

With respect to threats to the species caused by nonnative, invasive plant species, some land managers and private citizens implement invasive plant surveys, control, and monitoring, while others do not. Even with management, these species can be difficult to control without ample resources and time. Given that there are gaps in continuous geographic coverage regarding the management of nonnative, invasive species, populations of acuña cactus remain vulnerable to invasion.

With respect to threats to the species caused by activities along the U.S.-Mexico border, a number of documents such as Biological Opinions (e.g. Service 2009, 2011) dictate that certain actions be taken by CBP to reduce effects to resources in the U.S.-Mexico border region. These documents are primarily associated with habitat of the federally listed endangered Sonoran pronghorn antelope (

Antilocapra americana

ssp.

sonoriensis

) and off-road activity, specifically identifying sensitive areas to avoid. Such measures provide some relief from the threats caused to the species resulting from cross-border violators and CBP enforcement activities in the southern portion of the acuña cactus range. Likewise, CBP-sponsored projects, including the mapping of off-road tracks and revegetating unauthorized roads, may also benefit the acuña cactus (Holm 2012a, pers. comm.).

In cooperation with Service staff, CBP has begun efforts to educate Border Patrol agents on the locations and appearance of acuña cactus so that areas that support the species can be avoided to the maximum extent possible. A road atlas has been printed and distributed to CBP agents working in the area, although acuña cactus habitat is not indicated on this map (Morawe 2012, pers. comm.). In addition, the efforts of CBP to stop cross-border violators in recent years by means of traffic barriers and other infrastructure has greatly reduced cross-border violator activities and afforded some protection to the habitat. However, due to the difficulty and ever-changing status of border issues, compliance with these agreements has been difficult. Reports indicate a two-track road and associated cross-border violator clothing were found in 2010 within one of the six long-term monitoring plots at OPCNM. The cross-border violator activities are, by their very nature, in violation of the law and regulations. Therefore, regulations designed to protect the species and its habitat will be generally of little impact to alleviate the threats caused by activities of cross-border violators. As noted above, the interdiction efforts of the Border Patrol, including patrols, electronic surveillance, and fence construction have contributed to a significant reduction in cross-border violator off-road traffic that has benefited the acuña cactus and other species. However, we do not find regulatory mechanisms to be adequate to directly address these threats discussed in Factor A.

Factor E. Other Natural or Manmade Factors Affecting Its Continued Existence

We have evaluated the best scientific and commercial data available, and we did not find any indication of potential threats related to this factor. We considered such threats as small population size and overall rarity of the acuña cactus, but we did not find any indication that these are threats to the species. Therefore, we conclude that other natural or manmade factors are not threats to the acuña cactus.

Determination for the Acuña Cactus

We have carefully assessed the best scientific and commercial data available regarding the past, present, and future threats to the acuña cactus. We find that the species is in danger of extinction due to the current and ongoing modification and destruction of its habitat and range (Factor A) from long-term drought; effects of climate change; ongoing and future border activities; and future nonnative, invasive species issues. The acuña cactus habitat is impacted across its range by long-term drought, warmer winters occurring in the past several decades and projected to continue with climate change, and insect predation. In addition, the majority of the acuña cactus individuals (84 percent) occur within 16.5 km (10.25 mi) of the border in either OPCNM or Sonora, Mexico. As described above, the complexities of addressing off-road excursions by cross-border violators result in unpredictable actions on the part of CBP and law enforcement and threatens acuña cactus and its habitat. Furthermore, nonnative, invasive species have been located in the vicinity of several populations of acuña cactus and are projected to invade these populations within the next 5 to 20 years (Morawe 2012, pers. comm.).

The primary threats to the species are due to the effects of drought and climate change, and insect predation. These threats are exacerbated at local scales by off-road excursions by cross-border violators and CBP and law enforcement response, and will be impacted by nonnative, invasive plants in the future. We find that unauthorized collection (Factor B) does not currently occur to such an extent to constitute a threat to the species. We find that predation (Factor C), in combination with drought and heat stress, exacerbates the threats to this species. Although mechanisms are in place that afford some protection to the species and its habitat with regard to potential stressors to the species, no regulations are in place to address insect predation, drought, and the effects of climate change. With regard to off-road border activity, although the interdiction efforts of CBP, including patrols, electronic surveillance, and fence construction, have contributed to a significant reduction in cross-border violator off-road traffic that has benefited the acuña cactus and other species, regulations have little impact to alleviate these threats. Therefore, we do not find regulatory mechanisms to be adequate to directly address these threats discussed in Factor A. Finally, we find other natural or manmade

factors are not threats to the acuña cactus (Factor E).

The elevated risk of extinction of the acuña cactus is a result of the cumulative stressors on the species and its habitat. Mortality of more than 84 percent of individuals has been documented over a 24-year period within long-term monitoring plots at OPCNM. Mortality of more than 75 percent of individuals has been documented over a 21-year period at Coffeepot Mountain. These two examples of loss that has occurred on protected lands with ongoing management efforts for the acuña cactus show both a rapid and a severe decline of the species. In the acuña cactus, water and heat stress reduce flower and seed production, and seedling survival is dependent on summer precipitation and soil moisture. Warmer and drier winters combined with increased insect attack negatively impacts the survivorship of reproductive adults. Of the remaining living individuals across the species' range, a large portion were in various stages of deteriorating health, primarily blackening from the base upward, when visited by a botanist in 2011. Across populations, minimal or no recruitment has been seen in recent years. Throughout the species' range, rainfall has been declining, and drought conditions have been dominant for several decades; climate change is anticipated to increase drought periods and warming winters. This combination is expected to continue the documented trend of mortality exceeding recruitment across all populations. When mortality exceeds recruitment in a population, the result is often a declining population. Given this, we consider none of the populations to be stable or secure. The factors significantly threatening the species are not expected to be abated in the foreseeable future, and some populations may have decreased to levels where they are no longer viable. All of the threats, combined with high levels of mortality and low recruitment in the populations, contribute to a substantial risk of extinction and lead to our finding that the acuña cactus is in danger of extinction throughout its range; therefore, the acuña cactus meets the definition of an endangered species under the Act.

The Act defines an endangered species as any species that is “in danger of extinction throughout all or a significant portion of its range” and a threatened species as any species “that is likely to become endangered throughout all or a significant portion of its range within the foreseeable future.” We find that the acuña cactus is presently in danger of extinction throughout its entire range based on rangewide documented rapid loss of individuals, decline in the health of many remaining individuals, little to no recruitment, and continuation of the threats, as described above. Therefore, on the basis of the best scientific and commercial data available, we are listing the acuña cactus as an endangered species in accordance with sections 3(6) and 4(a)(1) of the Act.

Listing the acuña cactus as a threatened species is not the appropriate determination because the ongoing threats described above are severe enough to create the immediate risk of extinction. The continued loss of reproductive adults and juveniles poses a significant and immediate risk of extinction to the species throughout the species' range, and are not restricted to any particular significant portion of that range. All of these factors combined lead us to conclude that the threat of extinction is high and immediate; thus, we conclude that the acuña cactus meets the definition of an endangered species.

Under the Act and our implementing regulations, a species may warrant listing if it is an endangered or threatened species throughout all or a significant portion of its range. The threats to the survival of the species occur throughout the acuña cactus' range and are not restricted to any particular significant portion of that range. Accordingly, our assessment and final determination applies to the species throughout its entire range.

Fickeisen Plains Cactus

It is our intent to discuss below only those topics directly relevant to the listing of the Fickeisen plains cactus as endangered in this section of the final rule. As a result of public comments we received, we have updated the sections below as a result of information received during the public comment periods.

Species Description

The Fickeisen plains cactus is a small, unbranched to occasionally branched, globose (globular) cactus. At maturity, many plants are the size of a quarter making them difficult to locate even when their location is known. The stems of mature Fickeisen plains cactus are 2.5 to 6.5 cm (1.0 to 2.6 in) tall and up to 5.5 cm (2.2 in) in diameter (Heil and Porter 2003, p. 213; Arizona Rare Plant Guide Committee 2001, unpaginated); covered with tubercles (knoblike projections on the main stem) that form a spiral pattern around the plant (AGFD 2011a, p.1). Each tubercle has 6 to 7 radial spines per areole (tip where spines develop), 4 to 7 millimeters (mm) (0.15 to 0.27 in) in length, and 1 central spine (15 to 18 mm (0.59 to 0.70 in) long) that is straight to strongly curved. Spines are soft and corky (spongy) and white to pale gray in color. Flowers are 2.5 cm (0.98 in) in diameter, cream-yellow or yellowish-green in color, and produced on the apex (top) of the stem. Fruits are turbinate (top-shaped), and turn reddish-brown at maturity (AGFD 2011a, p. 1). The seeds are dark brown to black, 3 mm (0.11 in) long, and 2 mm (0.08 in) wide (AGFD 2011a, p. 1). The lifespan of the Fickeisen plains cactus is estimated to be between 10 to 15 years (Phillips

et al.

1982, p. 9).

Taxonomy

The Fickeisen plains cactus was first discovered near Cameron, Arizona, in the late 1950s. It was originally described in the scientific literature by Benson (1969, pp. 23-24), then later by Heil

et al.

(1981, pp. 28-31), who recognized the name and taxon in a review of the genus

Pediocactus.

The Flora of North America treats the taxon as a subspecies of

Pediocactus peeblesianus,

finding that the name “

Pediocactus peeblesianus

var.

fickeiseniae”

was not validly published by Benson (Heil and Porter 2003, p. 213). The difference between a subspecies and a variety based on the International Code of Botanical Nomenclature is that a subspecies has a higher rank in nomenclature. Some botanist or other taxonomic organizations may use the terms subspecies and variety interchangeably. The Service considers

Pediocactus peeblesianus

var.

fickeiseniae

to be a valid taxon since it was classified as a candidate species in 1980. Under the Act and in regard to plants, we treat subspecies and varieties equally (43 FR 17912) in that we do not differentiate between a subspecies or variety when assigning priority classifications to species for listing, delisting, reclassification, or recovery actions (43 FR 43103). Our previous documentation referring to the Fickeisen plains cactus used the name “

P. peeblesianus

var.

fickeiseniae”,

and we will continue to use this name. Other synonyms of

Pediocactus peeblesianus

var.

fickeiseniae

that have been used are

Navajoa fickeisenii

and

Toumeya fickeisenii

(Benson 1982, p. 955).

The genus

Pediocactus

contains nine species of cacti; eight of these are rare endemics of the Colorado Plateau region in Arizona, Colorado, New Mexico, and Utah (Heil and Porter 2003, p. 213). According to Benson (1982, p.750), the structural differences exhibited by

Pediocacti

among various sites, coupled with a poor seed dispersal mechanism and specializations to specific geology or soil type, indicate that the existing plants are probably relicts of a once widespread genus with a distribution fractured by climatic conditions. Although there are great dissimilarities among plants in the genus

Pediocactus,

they are united by their unusual method of fruit dehiscence and deciduous floral remnant (Heil

et al.

1981, p. 18). Within the species

Pediocactus peeblesianus

are two recognized varieties, variety

peeblesianus

(Peebles Navajo cactus) and variety

fickeiseniae.

The Fickeisen plains cactus is differentiated from the Peebles Navajo cactus by the presence of a central spine. The corky or spongy texture of the spines makes the species unique and separates it from other members in the genus (Heil

et al.

1981, p. 21). Chloroplast DNA sequencing further provides strong support of the separation of these two varieties (Porter 2002, pp. 15-16).

Biology

The general biology of the Fickeisen plains cactus is similar to other species in the genus

Pediocactus.

The Fickeisen plains cactus is a cold-adapted plant with contractile roots that enables the plant to retract into the soil during the winter (cold) and summer (dry) seasons, as well as during periods of drought conditions. Plants may shrink down into the soil until the crown sits flush with the soil surface. Some individuals may become completely buried by soil litter or gravel thus limiting the time plants can be found (Phillips

et al.

1982, p. 4). The general phenology is as follows: when ambient air temperatures rise in the spring and adequate rainfall occurs, plants emerge from beneath the soil surface to flower in mid-April. Flowers open in the mid-morning for 1 to 2 days. An entire population generally completes anthesis (the period when the flower is open and functional) in 7 to 14 days (Travis 1987, p. 6). Spring flowering is believed to be influenced by cold temperatures and precipitation from the preceding winter months (Brack 2012, pers. comm.), which enables moisture to accumulate in the soil during times when solar evaporation rates are low and may facilitate seedling germination. By June, plants will produce fruit then shrink back into the soil, losing one-half their height above ground. Plants generally remain retracted underground during the winter months; however, some individuals may re-emerge in the autumn following monsoonal rains. The length of time a plant remains retracted can vary between individual plants. Hughes (2000a, p. 2) has documented some plants remaining retracted underground for at least 3 years, but reported that a plant emerged after remaining retracted after 5 years (Hughes 2000, p.2). The Fickeisen plains cactus is also subject to root rot during very wet years and frost heaving during the winter season. Locating individuals of the Fickeisen plains cactus can be difficult, even when their exact location is known. Searches for individuals are best done during their flowering period.

Reproduction has not been specifically studied on the Fickeisen plains cactus. For other species in the genus

Pediocactus,

reproduction occurs through cross-pollination by native bees (Pimienta-Barrios and del Castillo 2002, p. 79). Insects observed visiting flowers of the Fickeisen plains cactus include species of hover flies (family Syrphidae) and bee flies (family Bombyliidae), mining bees (family Andrenidae), and sweat bees (family Halictidae) (Milne 1987, p. 21; Navajo Nation Heritage Program (NNHP) 1994, p. 3; Peach

et al.

1993, pp. 312-314; Tepedino 2000, p. 7). Although flies may pollinate flowers of the Fickeisen plains cactus, the primary pollinators of the plant are believed to be halictid bees from the genera

Lasioglossum, Halictus,

and

Agapostemon,

based on several studied species of

Pediocactus

(Tepedino 2012, pers. comm.).

The mechanisms of seed dispersal in the Fickeisen plains cactus have not been investigated and are poorly understood. Most site visits to areas occupied by the Fickeisen plains cactus have observed seedlings established very close to the adult plant (Goodwin 2011a, p. 9; NNHP 1994, p. 4). The general shared belief is that most species of

Pediocactus,

including the Fickeisen plains cactus, lack a good mechanism for seed dispersal, which is a contributing factor to its endemism and isolated, localized populations (Benson 1982, p. 750; Milne 1987, p. 4).

Population monitoring of the Fickeisen plains cactus suggests that this variety has a low reproductive capacity. Hughes (1996a, p. 50) reported that significant episodes of recruitment within the BLM monitoring plots occurred 2 to 3 times over a 9-year period from 1986 to 1995. He found that 30 to 40 seeds are generally produced from a single fruit (Hughes 2011, pers. comm.), and believed that low seed production hinders substantial increases in plant abundance from occurring, even during favorable weather conditions that would support germination (Hughes 1996a, p. 50). During the monitoring period, Hughes (1996a, p. 50) found that flowering and fruiting in the Fickeisen plains cactus occurs once individual plants reach 16 mm (0.63 in) in diameter and as the diameter increases more fruit are produced. He documented individuals between 20 mm (0.79 in) and 20.9 mm (0.82 in) in diameter that produced 1.37 fruit on average (range of fruit produced 1 to 3) compared to individuals at 50 mm (1.97 in) and larger that produced 3.60 fruits on average (range of fruit produced 2 to 5).

The correlation between larger sized individuals and increased fruit production has also been found in other

Pediocactus

species (Phillips

et al.

1989, p. 4; Hreha and Meyer 2001, p. 86), suggesting that larger, older individuals have a higher reproductive output and contribute more to the population growth rate by potentially having a greater influence on seed output than smaller, younger plants. In examining long-term monitoring information by the BLM, the majority of individuals observed tend to range between 20 mm (0.79 in) and 30 mm (1.18 in) in diameter, indicating at least 2 fruits should be produced per individual per year. Fruit production, however, occurred irregularly over a 22-year period with 35 percent, on average, of the total number of reproducing individuals. For comparison purposes, a population biology study on the

Pediocactus paradinei

(Kaibab plains cactus), which is similar in size to the Fickeisen plains cactus, summarized its population structure and found the following: plants between 11 to 20 mm diameters were pre-reproductive individuals that occasionally flowered but never fruited. Plants that were 21 to 30 mm were young reproductive individuals with lower reproductive effort than larger plants, and those 31 to 40 mm diameter and larger were older reproductive individuals with higher fruiting success (Warren

et al.

1992; p. 134).

Episodic recruitment may play a role in increasing the threats to the species because adult mortality may continue at a high rate between periods of recruitment, lowering the reproductive potential of the population when conditions are favorable for seed germination.

Habitat

The Fickeisen plains cactus is a narrow endemic restricted to exposed layers of Kaibab limestone on the Colorado Plateau. Plants are found in shallow, well-draining, gravelly loam soils formed from alluvium, colluvium, or Aeolian deposits derived from limestone of the Harrisburg Member of

the Kaibab Formation and Toroweap Formation; Coconino Sandstone; and the Moenkopi Formation (Travis 1987, pp. 2-3; Arizona Geological Survey (AZGS) 2011; Natural Resources Conservation Service (NRCS) 2012). Most populations occur on the margins of canyon rims, flat terraces, limestone benches, or on the toe of well-drained hills. Plants are found primarily on slopes of 0 to 5 percent but some also occur on slopes up to 20 percent at elevations between 1,280 to 1,814 m (4,200 to 5,950 ft) (Arizona Rare Plant Guide Committee 2001, unpaginated; AGFD 2011b, entire; Hazelton 2012a, pers. comm.; United States Forest Service (USFS) 2013b, p. 2).

Habitat of the Fickeisen plains cactus is within the Plains and Great Basin grasslands and Great Basin desertscrub vegetation communities (Benson 1982, p. 764; NatureServe 2011). Dominant native plant species that are commonly associated with these biotic communities include:

Artemisia tridentata

(big sagebrush),

Atriplex canescens

(four-wing saltbush),

Atriplex confertifolia

(shadscale),

Bouteloua eriopoda

(black grama),

Bouteloua gracilis

(blue grama),

Bromus

spp. (brome),

Chrysothamnus

spp. (rabbit-bush),

Ephedra torreyana

(Mormon tea),

Krascheninikovia lanata

(winterfat),

Gutierrezia sarothrae

(broom snakeweed),

Pleuraphis jamesii

(James's galleta),

Achnatherum hymenoides

(Indian ricegrass),

Sphaeralcea

spp. (globe-mallow), and

Stipa

spp. (needlegrass). Other native cactus species that are commonly found include

Agave utahensis

(Utah agave) and

Echinocactus polycephalus

(cottontop cactus; Brown 1994, pp. 115-121; Turner 1994, pp. 145-155; Hughes 1996b, p. 2; Goodwin 2011a, p. 4; NatureServe 2011). The

Escobaria vivipara

var.

rosea

(spinystar) is typically found in close association with the Fickeisen plains cactus (Hughes 1996a, p. 47). In addition, biological soil crusts are found on the Colorado Plateau and occur within or near the Fickeisen plains cactus populations (NRCS 1997, p. 3; USFS 1999, entire; BLM 2007a, p. 3-15).

Biological soil crusts are formed by a community of living organisms that can include cyanobacteria, green algae, microfungi, mosses, liverworts, and lichens (Belnap 2006, pp. 361-362). A preliminary soil assessment within occupied Fickeisen plains cactus habitat on the Kaibab Nation Forest suggested there are good biotic soil crusts in the general vicinity of the population and the microsites where cacti occur may have elevated macro and micro nutrient levels (MacDonald 2013, p. 1) potentially due to the presence of the biological soil crusts. The biological soil crusts provide many positive benefits to the other native vegetation within the Plains and Great Basin grassland community by providing fixed carbon and nitrogen on sparsely vegetated soils, soil stabilization and erosion control, water infiltration, improved plant growth, and seedling germination (NRCS 1997, pp. 8-10; Floyd

et al.

2003, p. 1704; Belnap 2006, entire).

The climate associated with the range

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