# Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for Chamaecrista lineata var. keyensis (Big Pine Partridge Pea), Chamaesyce deltoidea ssp. serpyllum (Wedge Spurge), Linum arenicola (Sand Flax), and Argythamnia blodgettii (Blodgett's Silverbush)

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URL: https://www.frixlaw.com/law-library/documents/fr%3A2022-21587

## Record

- **Collection:** Federal Register
- **Document type:** Proposed Rule
- **Published:** October 14, 2022
- **Citation:** 87 FR 62502

## Text

DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R4-ES-2022-0116; FF09E21000 FXES1111090FEDR 223]
RIN 1018-BE51

Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for
Chamaecrista lineata
var.
keyensis
(Big Pine Partridge Pea),
Chamaesyce deltoidea
ssp.
serpyllum
(Wedge Spurge),
Linum arenicola
(Sand Flax), and
Argythamnia blodgettii
(Blodgett's Silverbush)

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Proposed rule.

SUMMARY:

We, the U.S. Fish and Wildlife Service (Service), propose to designate critical habitat for
Chamaecrista lineata
var.
keyensis
(Big Pine partridge pea),
Chamaesyce deltoidea
ssp.
serpyllum
(wedge spurge),
Linum arenicola
(sand flax), and
Argythamnia blodgettii
(Blodgett's silverbush) under the Endangered Species Act (Act). In total, approximately 1,462 acres (592 hectares) for Big Pine partridge pea and approximately 1,379 acres (558 hectares) for wedge spurge, in Monroe County, Florida, and approximately 5,090 acres (2,060 hectares) for sand flax and 16,635 acres (6,732 hectares) for Blodgett's silverbush in Miami-Dade and Monroe Counties, Florida, fall within the boundaries of the proposed critical habitat designations. If we finalize this rule as proposed, it would extend the Act's protections to the species' critical habitat. We also announce the availability of a draft economic analysis of the proposed designation of critical habitat for these four plant species.

DATES:

We will accept comments received or postmarked on or before December 13, 2022. Comments submitted electronically using the Federal eRulemaking Portal (see
ADDRESSES
below) must be received by 11:59 p.m. eastern time on the closing date. We must receive requests for public hearings, in writing, at the address shown in
FOR FURTHER INFORMATION CONTACT
by November 28, 2022.

ADDRESSES:

You may submit comments by one of the following methods:

(1)
Electronically:
Go to the Federal eRulemaking Portal:
https://www.regulations.gov.
In the Search box, enter FWS-R4-ES-2022-0116, which is the docket number for this rulemaking action. Then, click on the Search button. On the resulting page, in the panel on the left side of the screen, under the Document Type heading, check the Proposed Rule box to locate this document. You may submit a comment by clicking on “Comment.”

(2)
By hard copy:
Submit by U.S. mail to: Public Comments Processing, Attn: FWS-R4-ES-2022-0116, U.S. Fish and Wildlife Service, MS: PRB/3W, 5275 Leesburg Pike, Falls Church, VA 22041-3803.

We request that you send comments only by the methods described above. We will post all comments on
https://www.regulations.gov.
This generally means that we will post any personal information you provide us (see Information Requested, below, for more information).

Availability of supporting materials:
For the proposed critical habitat designation, the coordinates or plot points or both from which the maps are generated are included in the decision file and are available at
https://www.fws.gov/office/florida-ecological-services/library
and at
https://www.regulations.gov
under Docket No. FWS-R4-ES-2022-0116. Any supporting information that we developed for this critical habitat designation will be available on the Service's website or at
https://www.regulations.gov.

FOR FURTHER INFORMATION CONTACT:

Lourdes Mena, Classification and Recovery Division Manager, U.S. Fish and Wildlife Service, Florida Ecological Services Field Office, 7915 Baymeadows Way, Suite 200, Jacksonville, FL 32256; by telephone 904-731-3134; or by facsimile 904-731-3045. Individuals in the United States who are deaf, deafblind, hard of hearing, or have a speech disability may dial 711 (TTY, TDD, or TeleBraille) to access telecommunications relay services. Individuals outside the United States should use the relay services offered within their country to make international calls to the point-of-contact in the United States.

SUPPLEMENTARY INFORMATION:

Executive Summary

Why we need to publish a proposed rule.
Under the Act, when we determine that any species is a threatened or endangered species, we must designate critical habitat, to the maximum extent prudent and determinable. Designations and revisions of critical habitat can only be completed by issuing a rule through the Administrative Procedure Act rulemaking process (5 U.S.C. 1531
et seq.
).

What this document does.
This document proposes to designate critical habitat for three plant species, Big Pine partridge pea, wedge spurge, and sand flax, listed as endangered species under the Act, and one plant species, Blodgett's silverbush, listed as a threatened species under the Act (September 29, 2016 (81 FR 66842)).

The basis for our action.
Section 3(5)(A) of the Act defines critical habitat as (i) the specific areas within the geographical area occupied by the species, at the time it is listed, on which are found those physical or biological features (I) essential to the conservation of the species and (II) which may require special management considerations or protections; and (ii) specific areas outside the geographical area occupied by the species at the time it is listed, upon a determination by the Secretary that such areas are essential for the conservation of the species. Section 4(b)(2) of the Act states that the Secretary must make the designation on the basis of the best scientific data available and after taking into consideration the economic impact, the impact on national security, and any other relevant impacts of specifying any particular area as critical habitat.

Draft economic analysis of the proposed designation of critical habitat.
We have prepared an analysis of the probable economic impacts of the proposed critical habitat designation and related factors. In this document, we announce the availability of the draft economic analysis and seek additional public review and comment.

Public comment.
We are seeking comments and soliciting information from the public on our proposed designation to make sure we consider the best scientific and commercial information available in developing our final designation. Because we will consider all comments and information we receive during the comment period, our final determination may differ from this proposal. We will respond to substantive comments we receive during the comment period in our final rule.

Peer review.
In accordance with our joint policy on peer review published in the
Federal Register
on July 1, 1994 (59 FR 34270), and our August 22, 2016, memorandum updating and clarifying the role of peer review of determinations under section 4 of the Act, including listing determinations and critical habitat designations, we are seeking comments from independent specialists. The purpose of peer review is to ensure that our critical habitat

designation is based on scientifically sound data, assumptions, and analyses. The peer reviewers have expertise in the biology, habitat, and threats to the species addressed herein. We have invited these peer reviewers to comment on our specific assumptions and conclusions in this critical habitat proposal during the public comment period for this proposed rule (see
DATES
, above).

Information Requested

We intend that any final action resulting from this proposed rule will be based on the best scientific and commercial data available and be as accurate and as effective as possible. Therefore, we request comments or information from other governmental agencies, Native American tribes, the scientific community, industry, or any other interested parties concerning this proposed rule. We particularly seek comments concerning:

(1) The reasons why we should or should not designate habitat as “critical habitat” under section 4 of the Act (16 U.S.C. 1531
et seq.
), including information regarding the following factors that the regulations identify as reasons why designation of critical habitat may be not prudent:

(a) The species is threatened by taking or other human activity and identification of critical habitat can be expected to increase the degree of such threat to the species; or

(b) Such designation of critical habitat would not be beneficial to the species. In determining whether a designation would not be beneficial, the factors the Services may consider include but are not limited to: whether the present or threatened destruction, modification, or curtailment of a species' habitat or range is not a threat to the species, or whether any areas meet the definition of “critical habitat.”

(2) Specific information on:

(a) The amount and distribution of Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush habitat.

(b) Any additional areas occurring within the range of the species,
i.e.,
south and central Florida peninsula and the Florida Keys, that should be included in the designation because they (i) were occupied at the time of listing in 2016 and contain the physical or biological features that are essential to the conservation of the species and that may require special management considerations, or (ii) were unoccupied at the time of listing, and are essential for the conservation of the species, because they have potential to successfully support introduced or reintroduced populations of these species.

(c) While we seek comments on any additional areas under (b)(i) and (ii) above, we particularly seek comments on the following unoccupied areas, including information on whether these areas have the potential to support introduced or reintroduced populations: No Name Key, Upper and Lower Sugarloaf Keys, Cudjoe Key, and Little Pine Key in Monroe County, Florida; and Trinity Pinelands, Nixon Smiley, Quail Roost Pineland, and Navy Wells in Miami-Dade County, Florida.

(d) Special management considerations or protection that may be needed in critical habitat areas we are proposing, including managing for the potential effects of climate change.

(e) Whether we have appropriately identified the physical or biological features that are essential to the conservation for each species.

(3) Land use designations and current or planned activities in the subject areas and their possible impacts on proposed critical habitat.

(4) Information on the projected and reasonably likely impacts of climate change on Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush and proposed critical habitat.

(5) Information on the extent to which the description of probable economic impacts in the draft economic analysis is a reasonable estimate of the likely economic impacts and any additional information regarding probable economic impacts that we should consider.

(6) Whether any specific areas we are proposing for critical habitat designation should be considered for exclusion under section 4(b)(2) of the Act, and whether the benefits of potentially excluding any specific area outweigh the benefits of including that area under section 4(b)(2) of the Act. If you think we should exclude any additional areas, please provide information regarding the existence of a meaningful economic or other relevant impact supporting a benefit of exclusion.

(7) Whether we could improve or modify our approach to designating critical habitat in any way to provide for greater public participation and understanding, or to better accommodate public concerns and comments.

Please include sufficient information with your submission (such as scientific journal articles or other publications) to allow us to verify any scientific or commercial information you include. Please note that submissions merely stating support for, or opposition to, the action under consideration without providing supporting information, although noted, will not be considered in making a final critical habitat determination. Section 4(b)(2) of the Act directs that the Secretary shall designate critical habitat on the basis of the best scientific information data available.

You may submit your comments and materials concerning this proposed rule by one of the methods listed in
ADDRESSES
. We request that you send comments only by the methods described in
ADDRESSES
.

If you submit information via
https://www.regulations.gov,
your entire submission—including any personal identifying information—will be posted on the website. If your submission is made via a hardcopy that includes personal identifying information, you may request at the top of your document that we withhold this information from public review. However, we cannot guarantee that we will be able to do so. We will post all hardcopy submissions on
https://www.regulations.gov.

Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on
https://www.regulations.gov.

Because we will consider all comments and information we receive during the comment period, our final designation may differ from this proposal. Based on the new information we receive (and any comments on that new information), our final designation may not include all areas proposed, may include some additional areas that meet the definition of critical habitat, or may exclude some areas if we find the benefits of exclusion outweigh the benefits of inclusion. Such final decisions would be a logical outgrowth of this proposal, as long as we: (1) base the decisions on the best scientific and commercial data available after considering all of the relevant factors; (2) do not rely on factors Congress has not intended us to consider; and (3) articulate a rational connection between the facts found and the conclusions made, including why we changed our conclusion.

Public Hearing

Section 4(b)(5) of the Act provides for a public hearing on this proposal, if requested. Requests must be received by the date specified in
DATES
. Such requests must be sent to the address shown in
FOR FURTHER INFORMATION CONTACT
. We will schedule a public hearing on this proposal, if requested, and announce the date, time, and place of the hearing, as well as how to obtain reasonable accommodations, in the

Federal Register
and local newspapers at least 15 days before the hearing. We may hold the public hearing in person or virtually via webinar. We will announce any public hearing on our website, in addition to the
Federal Register
. The use of virtual public hearings is consistent with our regulation at 50 CFR 424.16(c)(3).

Acronyms Used in This Document

For the convenience of the reader, we provide this list of some of the acronyms used in this proposed rule:

CCAA = candidate conservation agreements with assurances

CCP = comprehensive conservation plan

DoD = Department of Defense

ENP = Everglades National Park

FKWEA = Florida Keys Wildlife and Environmental Area

FNAI = Florida Natural Areas Inventory

HARB = Homestead Air Reserve Base

HCP = habitat conservation plan

INRMP = integrated natural resources management plan

KWNAS = Key West Naval Air Station

NKDR = National Key Deer Refuge

NWRs = National Wildlife Refuges

SHA = safe harbor agreements

SOCSO = Special Operations Command South

USDA = U.S. Department of Agriculture

Previous Federal Actions

On September 29, 2015, we proposed to list Big Pine partridge pea, wedge spurge, and sand flax as endangered species and Blodgett's silverbush as a threatened species under the Act (80 FR 58536). On September 29, 2016, we finalized the listing (81 FR 66842). At the time of our proposal, we determined that critical habitat was prudent, but not determinable because we lacked specific information on the impacts of our designation. In our final listing rule, we stated we were in the process of obtaining information on the impacts of the designation (81 FR 66842). All previous Federal actions for Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush are described in detail in our final rule listing the four plant species as endangered and threatened species under the Act (81 FR 66842).

It is our intent to discuss in this proposed rule only those topics directly relevant to the designation of critical habitat for Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush. For more information on the taxonomy, life history, habitat, population descriptions, and factors affecting the species, please refer to the September 29, 2015, proposed listing rule for these species (80 FR 58536) and the September 29, 2016, final listing rule (81 FR 66842).

Critical Habitat

Background

Section 4 of the Act (16 U.S.C. 1533) and the implementing regulations in title 50 of the Code of Federal Regulations set forth the procedures for determining whether a species is an endangered species or a threatened species, issuing protective regulations for threatened species, and designating critical habitat for threatened and endangered species. In 2019, jointly with the National Marine Fisheries Service, the Service issued final rules that revised the regulations in 50 CFR parts 17 and 424 regarding how we add, remove, and reclassify threatened and endangered species and the criteria for designating listed species' critical habitat (84 FR 45020 and 84 FR 44752; August 27, 2019). At the same time the Service also issued final regulations that, for species listed as threatened species after September 26, 2019, eliminated the Service's general protective regulations automatically applying to threatened species the prohibitions that section 9 of the Act applies to endangered species (collectively, the 2019 regulations).

However, on July 5, 2022, the U.S. District Court for the Northern District of California vacated the 2019 regulations (
Center for Biological Diversity
v.
Haaland,
No. 4:19-cv-05206-JST, Doc. 168 (N.D. Cal. July 5, 2022) (
CBD
v.
Haaland
)), reinstating the regulations that were in effect before the effective date of the 2019 regulations as the law governing species classification and critical-habitat decisions. Accordingly, in developing the analysis contained in this proposal, we applied the pre-2019 regulations, which may be reviewed in the 2018 edition of the Code of Federal Regulations at 50 CFR 424.02 and 424.12(a)(1) and (b)(2). Because of the ongoing litigation regarding the court's vacatur of the 2019 regulations, and the resulting uncertainty surrounding the legal status of the regulations, we also undertook an analysis of whether the proposal would be different if we were to apply the 2019 regulations. That analysis, which we described in a separate memo in the decisional file and posted on
https://www.regulations.gov,
concluded that we would have reached the same proposal if we had applied the 2019 regulations. For the four plants, we find that critical habitat is prudent under either regulatory scheme because we determined that the present or threatened destruction, modification, or curtailment of habitat or range is a threat to all four species. In addition, in the final listing rule (81 FR 66842; September 29, 2016), illegal collection of any of the four Florida Keys plants was not identified as a threat under Factor B, and identification and mapping of critical habitat is not expected to initiate any such threat. We also determined the occupied areas may be adequate to ensure the conservation of these species. For Blodgett's silverbush, the amount and distribution of critical habitat we are proposing for designation in occupied areas would allow existing and future established populations to maintain their existing distributions; expand their distributions into suitable nearby areas (needed to offset habitat loss and fragmentation); increase the size of each population to a level where the threats of genetic, demographic, and normal environmental uncertainties are diminished; and maintain their ability to withstand local or unit-level environmental fluctuations or catastrophic events. Accordingly, we have not identified unoccupied areas that are essential for the conservation of this species at this time. For Big Pine partridge pea, wedge spurge, and sand flax, we identified areas of remaining pine rockland habitat that we are considering whether these areas meet the definition of unoccupied critical habitat for these three species.

On September 21, 2022, the U.S. Circuit Court of Appeals for the Ninth Circuit stayed the district court's July 5, 2022, order vacating the 2019 regulations until a pending motion for reconsideration before the district court is resolved (
In re: Cattlemen's Ass'n,
No. 22-70194). The effect of the stay is that the 2019 regulations are currently the governing law. Because a court order requires us to submit this proposal to the
Federal Register
by September 30, 2022, it is not feasible for us to revise the proposal in response to the Ninth Circuit's decision. Instead, we hereby adopt the analysis in the separate memo that applied the 2019 regulations as our primary justification for the proposal. However, due to the continued uncertainty resulting from the ongoing litigation, we also retain the analysis in this preamble that applies the pre-2019 regulations and we conclude that, for the reasons stated in our separate memo analyzing the 2019 regulations, this proposal would have been the same if we had applied the 2019 regulations.

Critical habitat is defined in section 3 of the Act as:

(1) The specific areas within the geographical area occupied by the species, at the time it is listed in accordance with the Act, on which are found those physical or biological features

(a) Essential to the conservation of the species, and

(b) Which may require special management considerations or protection; and

(2) Specific areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.

Our regulations at 50 CFR 424.02 define the geographical area occupied by the species as an area that may generally be delineated around species' occurrences, as determined by the Secretary (
i.e.,
range). Such areas may include those areas used throughout all or part of the species' life cycle, even if not used on a regular basis (
e.g.,
migratory corridors, seasonal habitats, and habitats used periodically, but not solely by vagrant individuals).

Conservation, as defined under section 3 of the Act, means to use and the use of all methods and procedures that are necessary to bring an endangered or threatened species to the point at which the measures provided pursuant to the Act are no longer necessary. Such methods and procedures include, but are not limited to, all activities associated with scientific resources management such as research, census, law enforcement, habitat acquisition and maintenance, propagation, live trapping, and transplantation, and, in the extraordinary case where population pressures within a given ecosystem cannot be otherwise relieved, may include regulated taking.

Critical habitat receives protection under section 7 of the Act through the requirement that Federal agencies ensure, in consultation with the Service, that any action they authorize, fund, or carry out is not likely to result in the destruction or adverse modification of critical habitat. The designation of critical habitat does not affect land ownership or establish a refuge, wilderness, reserve, preserve, or other conservation area. Designation also does not allow the government or public to access private lands, nor does designation require implementation of restoration, recovery, or enhancement measures by non-Federal landowners. Where a landowner requests Federal agency funding or authorization for an action that may affect a listed species or critical habitat, the Federal agency would be required to consult with the Service under section 7(a)(2) of the Act. However, even if the Service were to conclude that the proposed activity would result in destruction or adverse modification of the critical habitat, the Federal action agency and the landowner are not required to abandon the proposed activity, or to restore or recover the species; instead, they must implement “reasonable and prudent alternatives” to avoid destruction or adverse modification of critical habitat.

Under the first prong of the Act's definition of critical habitat, areas within the geographical area occupied by the species at the time it was listed are included in a critical habitat designation if they contain physical or biological features (1) which are essential to the conservation of the species and (2) which may require special management considerations or protection. For these areas, critical habitat designations identify, to the extent known using the best scientific and commercial data available, those physical or biological features that are essential to the conservation of the species (such as space, food, cover, and protected habitat). In identifying those physical or biological features that occur in specific occupied areas, we focus on those features that are essential to support the life-history needs of the species, including, but not limited to, water characteristics, soil type, geological features, prey, vegetation, symbiotic species, or other features. A feature may be a single habitat characteristic or a more complex combination of habitat characteristics. Features may include habitat characteristics that support ephemeral or dynamic habitat conditions. Features may also be expressed in terms relating to principles of conservation biology, such as patch size, distribution distances, and connectivity.

Under the second prong of the Act's definition of critical habitat, we can designate critical habitat in areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.

Section 4 of the Act requires that we designate critical habitat on the basis of the best scientific data available. Further, our Policy on Information Standards Under the Endangered Species Act (published in the
Federal Register
on July 1, 1994 (59 FR 34271)), the Information Quality Act (section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 106-554; H.R. 5658)), and our associated Information Quality Guidelines provide criteria, establish procedures, and provide guidance to ensure that our decisions are based on the best scientific data available. They require our biologists, to the extent consistent with the Act and with the use of the best scientific data available, to use primary and original sources of information as the basis for recommendations to designate critical habitat.

When we are determining which areas should be designated as critical habitat, our primary source of information is generally the information from the listing process for the species. Additional information sources may include any generalized conservation strategy, criteria, or outline that may have been developed for the species; the recovery plan for the species; articles in peer-reviewed journals; conservation plans developed by States and counties; scientific status surveys and studies; biological assessments; other unpublished materials; or experts' opinions or personal knowledge.

Habitat is dynamic, and species may move from one area to another over time. We recognize that critical habitat designated at a particular point in time may not include all of the habitat that we may later determine are necessary for the recovery of the species. For these reasons, a critical habitat designation does not signal that habitat outside the designated area is unimportant or may not be needed for recovery of the species. Areas that are important to the conservation of the species, both inside and outside the critical habitat designation, will continue to be subject to: (1) Conservation actions implemented under section 7(a)(1) of the Act; (2) regulatory protections afforded by the requirement in section 7(a)(2) of the Act for Federal agencies to ensure their actions are not likely to jeopardize the continued existence of any endangered or threatened species; and (3) section 9 of the Act's prohibitions on taking any individual of the species, including taking caused by actions that affect habitat. Federally funded or permitted projects affecting listed species outside their designated critical habitat areas may still result in jeopardy findings in some cases. These protections and conservation tools will continue to contribute to recovery of the species. Similarly, critical habitat designations made on the basis of the best available information at the time of designation will not control the direction and substance of future recovery plans, habitat conservation plans (HCPs), or other species conservation planning efforts if new information available at the time of those planning efforts calls for a different outcome.

Prudency Determination

Section 4(a)(3) of the Act, as amended, and implementing regulations

(50 CFR 424.12) require that, to the maximum extent prudent and determinable, the Secretary shall designate critical habitat at the time the species is determined to be an endangered or threatened species. Our regulations (50 CFR 424.12(a)(1)) state that a designation of critical habitat is not prudent when any of the following situations exist:

(i) The species is threatened by taking or other human activity, and identification of critical habitat can be expected to increase the degree of such threat to the species; or

(ii) Such designation of critical habitat would not be beneficial to the species. In determining whether a designation would not be beneficial, the factors the Services may consider include but are not limited to: Whether the present or threatened destruction, modification, or curtailment of a species' habitat or range is not a threat to the species, or whether any areas meet the definition of “critical habitat.”

As discussed in the final listing rule (81 FR 66842), there is currently no imminent threat of take attributed to collection or vandalism identified under Factor B for these species, and identification and mapping of critical habitat is not expected to initiate or increase the degree of any such threat. In our listing determination for these species, we determined that the present or threatened destruction, modification, or curtailment of habitat or range is a threat to these species. Accordingly, the designation of critical habitat is likely to be beneficial. Therefore, because none of the circumstances enumerated in our regulations at 50 CFR 424.12(a)(1) have been met, we have determined that the designation of critical habitat is prudent for Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush.

Critical Habitat Determinability

Having determined that designation of critical habitat is prudent for each species, under section 4(a)(3) of the Act, we must find whether critical habitat for Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush is determinable. Our regulations at 50 CFR 424.12(a)(2) state that critical habitat is not determinable when one or both of the following situations exist:

(i) Data sufficient to perform required analyses are lacking, or

(ii) The biological needs of the species are not sufficiently well known to identify any area that meets the definition of “critical habitat.”

When critical habitat is not determinable, the Act allows the Service an additional year to publish a critical habitat designation (16 U.S.C. 1533(b)(6)(C)(ii)).

At the time of our proposal, we determined that critical habitat was prudent, but not determinable because we lacked specific information on the impacts of our designation (80 FR 58536). In our final listing rule, we stated we were in the process of obtaining information on the impacts of the designation (81 FR 66842). We reviewed the available information pertaining to the biological needs of the species and habitat characteristics where these species are located. This and other information represent the best scientific data available and led us to conclude that the designation of critical habitat is determinable for Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush.

Physical or Biological Features

In accordance with section 3(5)(A)(i) of the Act and regulations at 50 CFR 424.12(b), in determining which areas we will designate as critical habitat from within the geographical area occupied by the species at the time of listing, we consider the physical or biological features that are essential to the conservation of the species and that may require special management considerations or protection. The regulations at 50 CFR 424.02 define “physical or biological features” as the features that support the life-history needs of the species, including, but not limited to, water characteristics, soil type, geological features, sites, prey, vegetation, symbiotic species, or other features. A feature may be a single habitat characteristic or a more complex combination of habitat characteristics. Features may include habitat characteristics that support ephemeral or dynamic habitat conditions. Features may also be expressed in terms relating to principles of conservation biology, such as patch size, distribution distances, and connectivity. For example, physical features essential to the conservation of the species might include gravel of a particular size required for spawning, alkali soil for seed germination, protective cover for migration, or susceptibility to flooding or fire that maintains necessary early-successional habitat characteristics. Biological features might include prey species, forage grasses, specific kinds or ages of trees for roosting or nesting, symbiotic fungi, or absence of a particular level of nonnative species consistent with conservation needs of the listed species. The features may also be combinations of habitat characteristics and may encompass the relationship between characteristics or the necessary amount of a characteristic essential to support the life history of the species.

In considering whether features are essential to the conservation of the species, the Service may consider an appropriate quality, quantity, and spatial and temporal arrangement of habitat characteristics in the context of the life-history needs, condition, and status of the species. These characteristics include, but are not limited to, space for individual and population growth and for normal behavior; food, water, air, light, minerals, or other nutritional or physiological requirements; cover or shelter; sites for breeding, reproduction, or rearing (or development) of offspring; and habitats that are protected from disturbance.

We derive the specific physical or biological features essential to Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush from studies of the species' habitat, ecology, and life history as described below. Additional information can be found in the September 29, 2015, proposed listing rule (80 FR 58536) and the September 29, 2016, final listing rule (81 FR 66842) for these species. We have determined that the following physical or biological features are essential to the conservation of Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush.

Big Pine Partridge Pea, Wedge Spurge, and Sand Flax

Space for Individual and Population Growth and for Normal Behavior

Plant Community and Competitive Ability

Big Pine partridge pea, wedge spurge, and sand flax occur in the lower Florida Keys in Monroe County in communities classified as pine rockland and on disturbed sites adjacent to pine rocklands, such as roadside and mowed areas still dominated by native species (see more detailed description of disturbed sites below). In addition, sand flax occurs on the Miami Rock Ridge in Miami-Dade County in pine rockland, on disturbed sites adjacent to pine rockland, and on two canal banks that likely incorporated pine rockland substrate as fill (Bradley and Gann 1999, p. 61; Hodges and Bradley 2006, p. 37). These communities and their associated native plant species are described in the Background section of the September 29, 2015, proposed listing rule (80 FR 58536) and in the September 29, 2016, final listing rule (81 FR 66842) for Big Pine partridge pea, wedge spurge, and sand flax. These habitats and their associated plant communities provide

vegetation structure that allows for adequate growing space, moisture, sunlight, pollinators, and a competitive regime that is required for Big Pine partridge pea, wedge spurge, and sand flax to persist and spread.

Pine rocklands are a fire-maintained ecosystem characterized by an open canopy, understory, and a limestone substrate (often exposed). Open canopy conditions are required to allow sufficient sunlight to reach the herbaceous layer and permit growth and flowering of Big Pine partridge pea, wedge spurge, and sand flax (Ross and Ruiz 1996, pp. 5-6; Bradley and Saha 2009, p. 4). These species also require a calcareous limestone substrate that varies from nearly bare to thin layers or small pockets of shallow soil to provide suitable growing conditions (
e.g.,
pH, nutrients, anchoring, and proper drainage). As a result of these marginal soil conditions, plants such as Big Pine partridge pea, wedge spurge, and sand flax rely on sparse competition and periodic disturbance to thrive and persist. This combination of ecosystem characteristics (
i.e.,
open canopy with a partially exposed limestone substrate and periodic disturbance) occurs only in pine rockland habitats (as opposed to rockland hammock, which occurs in conjunction with pine rockland and has a limestone substrate but a closed canopy).

Disturbed areas that support Big Pine partridge pea, wedge spurge, and sand flax consist of sites that formerly were pine rocklands, but in most cases have no remaining pine canopy because of previous disturbance from clearing or scraping. In addition, some disturbed areas that support sand flax are sites where pine rockland substrate was used as fill. These include roadsides, firebreaks, and other areas that are infrequently mowed, or have no pine canopy but retain native pine rockland herbs, grass species, and substrate (Bradley and van der Heiden 2013, pp. 7-12; Bradley 2006, p. 37: Bradley and Gann 1999, p. 61).

Sand flax occurrences reported from marl prairie are at sites that have been artificially drained (Bradley and Van Der Heiden 2013, p. 11) or are scraped pine rocklands that function more like marl prairie (Kernan and Bradley 1996, p. 11). As with disturbed roadside habitats, it is possible that dry marl prairies have become refugia for the sand flax as fire regimes and natural areas were altered and destroyed over the last century. However, the Service does not consider marl prairie to be a primary habitat for sand flax.

The total remaining area of pine rockland in the lower Florida Keys (Monroe County) is now approximately 1,899 acres (ac) (769 hectares (ha)), most of which is on Big Pine Key (1,480 ac (599 ha)) (U.S. Geological Survey (USGS) 2019). In mainland south Florida (Miami-Dade County), development and agriculture have reduced pine rockland habitat by 90 percent. Recent vegetation mapping in Everglades National Park (ENP) indicates there are a total of 14,211 ac (5,751 ha) of pine rocklands remaining in ENP, which includes the largest remaining area of pine rockland (approximately 10,895 ac (4,409 ha)) in Florida (Long Pine Key) (Ruiz 2022). Outside of ENP, pine rockland habitat decreased from approximately 185,329 ac (75,000 ha) in the early 1900s to only 3,707 ac (1,500 ha) in 2014 (Possley et al. 2014, p. 154) and 2,275 ac (921 ha) in 2019 (USGS 2019), leaving only about 1.2 percent of the pine rocklands on the Miami Rock Ridge remaining, and much of what is left are small remnants scattered throughout the Miami metropolitan area, isolated from other natural areas (Herndon 1998, p. 1). Based on the data presented above, outside of ENP the total remaining area of pine rockland in Miami-Dade and Monroe Counties is now 4,174 ac (1,689 ha) (approximately 2,275 ac (921 ha) in Miami-Dade County and 1,899 ac (769 ha) in the Florida Keys (Monroe County)). The extreme rarity of high-quality pine rockland habitat supporting Big Pine partridge pea, wedge spurge, and sand flax elevates the importance of disturbed remnant sites that still retain some pine rockland species.

We consider pine rockland to be the primary habitat for Big Pine partridge pea, wedge spurge, and sand flax. However, adjacent disturbed areas currently supporting the species are considered essential when adjacent pine rocklands do not support an existing population or are of insufficient size or connectivity to support a population of Big Pine partridge pea, wedge spurge, and sand flax. Therefore, based on the information above, we identify upland habitats consisting of pine rocklands and adjacent disturbed areas to be a physical or biological feature essential to the conservation of these species.

Food, Water, Air, Light, Minerals, or Other Nutritional or Physiological Requirements

Climate (Temperature and Precipitation)

Big Pine partridge pea, wedge spurge, and sand flax require adequate rainfall and do not tolerate prolonged freezing temperatures. The climate of south Florida where these species occur is characterized by distinct wet and dry seasons, a monthly mean temperature above 64.4°F (F) (18° Celsius (C)) in every month of the year, and annual rainfall averaging 30 to 60 inches (in) (75 to 150 centimeters (cm)) (Gabler et al. 1994, p. 211). Rainfall within the range of sand flax varies from an annual average of 60-65 in (153-165 cm) in the northern portion of the Miami Rock Ridge to an average of 35-40 in (89-102 cm) in the lower Florida Keys (Snyder et al. 1990, p. 238). Areas of pine rockland that are adjacent to wetlands may experience prolonged flooded periods lasting up to 60 days, while those at higher elevation have shorter or no annual flooding period (Florida Natural Areas Inventory (FNAI) 2010a, p. 2). Freezes can occur in the winter months but are very infrequent at this latitude in Florida. Therefore, based on the information above, we determined a subtropical humid (Miami-Dade County) or tropical humid (Monroe County) climate to be an essential physical feature for Big Pine partridge pea, wedge spurge, and sand flax.

Soils

Substrates supporting Big Pine partridge pea, wedge spurge, and sand flax are composed of oolitic limestone that is at or very near the surface. Solution holes occasionally form where the surface limestone is dissolved by organic acids. There is typically very little soil development, consisting primarily of accumulations of low-nutrient sand, marl, clayey loam, and organic debris found in solution holes, depressions, and crevices on the limestone surface (FNAI 2010a, p. 62). However, extensive sandy pockets can be found at the northern end of the Miami Rock Ridge, beginning from approximately North Miami Beach and extending south to approximately SW 216 Street (which runs east-west approximately one-half mile south of Quail Roost Pineland) (Service 1999, p. 3-162).

These substrates provide anchoring, nutrients, moisture regime, and suitable soil chemistry for Big Pine partridge pea, wedge spurge, and sand flax; they facilitate a community of associated plant species that creates competition which allows Big Pine partridge pea, wedge spurge, and sand flax to persist and spread. Therefore, based on the information above, we identify substrates derived from calcareous limestone (often exposed with little soil development) that provide nutritional requirements and suitable growing conditions (
e.g.,
pH, nutrients, anchoring and drainage) to be an essential physical feature for Big Pine

partridge pea, wedge spurge, and sand flax.

Cover or Shelter

As mentioned previously, Big Pine partridge pea, wedge spurge, and sand flax occur in pine rocklands and adjacent disturbed areas in the lower Florida Keys (Bradley and Gann 1999, pp. 17-18; Bradley 2006, p. 21). In addition, sand flax occurs in pine rocklands on the Miami Rock Ridge in Miami-Dade County. These pine rocklands are characterized by an open canopy of
Pinus elliottii
var.
densa
(South Florida slash pine). The shrub/understory layer is also characteristically open, although the height and density of the shrub layer varies based on fire frequency, with understory plants growing taller and denser as time since fire increases. The open canopy and understory of pine rocklands are required to allow sufficient sunlight to reach the herbaceous layer and permit growth and flowering of Big Pine partridge pea, wedge spurge, and sand flax (Bradley and Gann 1999, pp. 17-18; Bradley 2006, p. 37).

Disturbed areas that are adjacent to pine rocklands that support Big Pine partridge pea, wedge spurge, and sand flax may have little to no pine canopy, but an herbaceous layer dominated by native herbs and grasses. Usually, these are former (remnant) pine rocklands that have a history of disturbance (clearing or scraping). These sites tend to be infrequently (every 2-3 months) mowed areas adjacent to existing pine rocklands, such as roadsides and fields. These areas can provide the open conditions required by Big Pine partridge pea, wedge surge, and sand flax (Bradley 2006, p. 37).

Therefore, based on the information above, we identify vegetation composition and structure characterized by an open canopy of South Florida slash pine and understory that allows for sufficient sunlight and space for individual growth and population expansion to be an essential feature for Big Pine partridge pea, wedge spurge, and sand flax.

Sites for Breeding, Reproduction, or Rearing (or Development) of Offspring

Big Pine partridge pea reproduction is sexual, and flowers require insect visitation for pollination. Though many types of insects visit Big Pine partridge pea flowers, effective pollination can be performed only by buzz-pollinating bees (Liu and Koptur 2003, pp. 1184-1186). Seed production is higher when cross-pollination occurs. In addition, seed germination rates are higher from cross-pollinated flowers, suggesting that inbreeding depression occurs in seeds produced through self-pollination (Liu and Koptur 2003, pp. 1184-1186). Taken together, these findings indicate that insect pollination is crucial to the plant's reproduction and progeny fitness. Declines in pollinator visitation may cause decreased seed production, which could lead to lower seedling establishment and numbers of mature plants.

The biology and demography of wedge spurge have received considerable study. Small groups of the plant are scattered widely across the pine rocklands of Big Pine Key (Herndon 1993, in Bradley and Gann 1999, p. 31), with a population estimated at 368,557 in 2014 (Bradley et al. 2015, p. 21). The population was confirmed to still be present in 2019 (Lange et al. 2019, p. 16). Wedge spurge reproduction is sexual and likely requires insect visitation for pollination. Other species of
Chamaesyce
are completely reliant on insects for pollination and seed production while others are capable of self-pollination. Pollinators may include bees, flies, ants, and wasps (Ehrenfeld 1976, pp. 95-97, 406).

Little is known about the life history of sand flax, including pollination biology, seed production, or dispersal. Sand flax reproduction is sexual, with new plants generated from seeds. A recent study found that pollinators are important in fruit production of sand flax (Harris and Koptur 2022, pp. 7-8). Effective pollination has been found from small bees and flies that visit the flowers of sand flax (Harris and Koptur 2022, pp. 4-6). This recent information suggests that insect pollination is important to the species' reproduction. Therefore, like Big Pine partridge pea and wedge spurge, declines in pollinator visitation may cause decreased seed or fruit production of sand flax, which could lead to lower seedling establishment and numbers of mature plants.

The pine rocklands and adjacent disturbed habitats identified above as essential physical or biological features provide a plant community with associated plant species that foster a competitive regime suitable to Big Pine partridge pea, wedge spurge, and sand flax and contain adequate open space for the recruitment of new plants. Associated plant species in these habitats attract and provide cover for insect pollinators required for Big Pine partridge pea pollination, wedge spurge, and sand flax.

Therefore, based on the information above, we identify pine rockland habitat and adjacent disturbed areas containing the presence of native pollinators for natural pollination and reproduction to be an essential feature for Big Pine partridge pea, wedge spurge, and sand flax.

Habitats Representative of the Historical, Geographical, and Ecological Distributions of the Species

Big Pine partridge pea, wedge spurge, and sand flax continue to occur in habitats that are representative of the species' historical, geographical, and ecological distribution, although their current ranges have been reduced. These species are currently found in pine rocklands, and they also occur in adjacent disturbed areas, such as roadsides. As described above, these habitats provide a community of associated plant and animal species that are compatible with Big Pine partridge pea, wedge spurge, and sand flax. In addition, these habitats provide the vegetation structure that provides adequate sunlight levels and open space for plant growth and regeneration, and substrates with adequate moisture availability and suitable soil chemistry needed for these species. Representative communities are located on Federal, State, local, and private conservation lands that implement conservation measures benefitting these species.

Disturbance Regime

Pine rockland habitat that could support or currently supports Big Pine partridge pea, wedge spurge, and sand flax depend on a disturbance regime of wild or prescribed fire to open the canopy in order to provide light levels sufficient to support these species. Fire return intervals of 5 to 7 years generate the lowest extinction and population decline probabilities for Big Pine partridge pea (Liu et al. 2005, p. 210). The historical frequency and magnitude of fire allowed for the persistence of Big Pine partridge pea, wedge spurge, and sand flax by maintaining an open canopy and understory and preventing succession (transition) of pine rocklands to hardwood-dominated community (rockland hammock). In the absence of fire, some areas of pine rockland may have closed canopies, resulting in areas lacking enough available sunlight to support Big Pine partridge pea, wedge spurge, and sand flax. Most of these areas can be enhanced if habitats are managed with a combination of mechanical hardwood removal and prescribed fire. Disturbed sites that support Big Pine partridge pea, wedge spurge, and sand flax are typically maintained by infrequent mowing. Mowing is similar in effect to fire in that

it limits encroachment of hardwood species and maintains open canopy conditions suitable for these species. We consider wildfire to be the natural disturbance factor for pine rocklands and Big Pine partridge pea, wedge spurge, and sand flax. In adjacent disturbed areas currently supporting the species, mowing serves some of the ecological function of fire and maintains suitable habitat conditions (open canopy) for these species.

Therefore, based on the information above, we identify periodic natural (
e.g.,
fire) or nonnatural (
e.g.,
prescribed fire, mowing) disturbance regimes to maintain open canopy conditions in South Florida pine rocklands, to be an important process to maintain essential features for Big Pine partridge pea, wedge spurge, and sand flax.

Summary of Physical or Biological Features Essential to the Conservation of Big Pine Partridge Pea, Wedge Spurge, and Sand Flax

Based on the best available science related to the life history and ecology of these species, as outlined in the discussion above, we have determined that the following physical or biological features are essential to the conservation of Big Pine partridge pea, wedge spurge, and sand flax:

South Florida pine rockland habitat and adjacent disturbed areas:

(1) Consisting of calcareous limestone substrate (often exposed with little soil development) that provides nutritional requirements and suitable growing conditions (
e.g.,
pH, nutrients, anchoring and drainage);

(2) Characterized by an open canopy of
Pinus elliottii
var.
densa
(South Florida slash pine) and understory with a high proportion of native pine rockland plant species to provide for sufficient sunlight to permit growth and flowering;

(3) Subjected to a monthly mean temperature characteristic of the subtropical humid classification in Miami-Dade County and tropical humid classification in Monroe County in every month of the year and short hydroperiods ranging of up to 60 days each year;

(4) Subjected to periodic natural (
e.g.,
fire) or nonnatural (
e.g.,
prescribed fire, mowing) disturbance regimes to maintain open canopy conditions; and

(5) Containing the presence of native pollinators for natural pollination and reproduction.

Blodgett's Silverbush

Space for Individual and Population Growth and for Normal Behavior

Plant Community and Competitive Ability

Blodgett's silverbush occurs in the Florida Keys in Monroe County and on the Miami Rock Ridge in Miami-Dade County in communities classified as pine rockland, rockland hammock, and coastal berm, as well as disturbed sites adjacent to these habitats, such as roadsides and mowed areas still dominated by native species (Bradley and Gann 1999, p. 3). These communities and their associated native plant species are described in the final listing rule for Blodgett's silverbush published in the
Federal Register
on September 29, 2016 (81 FR 66842). These habitats and their associated plant communities provide vegetation structure that allows for adequate growing space, moisture, sunlight, pollinators, and a competitive regime that is required for Blodgett's silverbush to persist and spread. As discussed above for Big Pine partridge pea, wedge spurge, and sand flax, pine rocklands are a fire-maintained ecosystem characterized by an open canopy and understory and a limestone substrate (often exposed). Rockland hammock is a species-rich tropical hardwood forest on upland sites in areas where limestone is very near the surface and often exposed. Coastal berms are landscape features found along low-energy coastlines in south Florida and the Florida Keys. Coastal berm is a short forest or shrub thicket found on long, narrow, storm-deposited ridges (sand dunes) of loose sediment formed by a mixture of coarse shell fragments, pieces of coralline algae, and other coastal debris.

Similar to the other species, open canopy conditions are required to allow sufficient sunlight to reach the herbaceous layer and permit growth and flowering of Blodgett's silverbush. These conditions are maintained by fire in pine rocklands. In rockland hammocks, only the edges and canopy disruption in the interior provide enough sunlight for Blodgett's silverbush. Canopy disruption on rockland hammocks can occur due to natural events such as hurricanes and storm surge. Human disturbance, especially mowing, also maintains suitable conditions in disturbed areas, as discussed above for Big Pine partridge pea, wedge spurge, and sand flax. The plant also requires a calcareous limestone substrate that varies from nearly bare to thin layers or small pockets of shallow soil in pine rocklands, to shallow organic soils over calcareous limestone in rockland hammocks, and deep, calcareous sandy soils typical of coastal berm to provide suitable growing conditions (
e.g.,
pH, nutrients, anchoring, and proper drainage). As a result of these marginal soil conditions, plants such as Blodgett's silverbush rely on sparse competition and periodic disturbance to thrive and persist. This combination of ecosystem characteristics (
i.e.,
open canopy and limestone substrate) occurs in pine rocklands, along edges and gaps in rockland hammocks, and in coastal berm.

Disturbed areas that support Blodgett's silverbush consist of sites that formerly were pine rocklands or rockland hammocks, but in most cases have no remaining pine or hardwood canopy because of previous disturbance (clearing or scraping). These include roadsides, firebreaks, and other areas that are infrequently mowed or have no tree canopy but retain native herbs, grass species, and substrate (Bradley 2006, p. 37: Bradley and Gann 1999, p. 61).

Loss of pine rockland habitat in Miami-Dade and Monroe County is discussed above for Big Pine partridge pea, wedge spurge, and sand flax. In addition, modification and destruction from residential and commercial development have severely impacted rockland hammocks and coastal berm that support Blodgett's silverbush. Rockland hammocks were once abundant in Miami-Dade and Monroe Counties but are now considered imperiled locally and globally (FNAI 2010b, pp. 24-26). The tremendous development and agricultural pressures in south Florida have resulted in significant reductions of rockland hammock (Phillips 1940, p. 167; Snyder et al. 1990, pp. 271-272; FNAI 2010b, pp. 24-26).

The extreme rarity of high-quality pine rockland, rockland hammock, and coastal berm habitat supporting Blodgett's silverbush in Miami-Dade and Monroe Counties elevates the importance of disturbed remnant sites that still retain some habitat values.

We consider pine rocklands, edges or gaps in rockland hammocks, and coastal berm to be the primary habitats for Blodgett's silverbush. However, adjacent disturbed areas currently supporting the species are considered more important when adjacent pine rocklands, rockland hammocks, or coastal berm do not support an existing population, or are of insufficient size or connectivity to support a population of Blodgett's silverbush. Therefore, based on the information above, we identify upland

habitats consisting of pine rocklands, rockland hammocks, coastal berms, and adjacent disturbed areas to be physical or biological features essential to the conservation of Blodgett's silverbush.

Food, Water, Air, Light, Minerals, or Other Nutritional or Physiological Requirements

Climate (Temperature and Precipitation)

Blodgett's silverbush requires adequate rainfall and does not tolerate prolonged freezing temperatures. The climate of south Florida where Blodgett's silverbush occurs is classified as subtropical humid (Miami-Dade County) and tropical humid (Monroe County), as described above for Big Pine partridge pea, wedge spurge, and sand flax. Rainfall within the range of Blodgett's silverbush varies from an annual average of 60-65 in (153-165 cm) in the northern portion of the Miami Rock Ridge to an average of 35-40 in (89-102 cm) in the lower Florida Keys (Snyder et al. 1990, p. 238). Areas of pine rockland that are adjacent to wetlands may experience prolonged flooded periods lasting up to 60 days, while those at higher elevation have shorter or no annual flooding period (FNAI 2010a, p. 2). Freezes can occur in the winter months but are very infrequent at this latitude in Florida. Therefore, based on the information above, we determined this type of climate to be an essential physical feature for Blodgett's silverbush.

Soils

Substrates supporting Blodgett's silverbush are composed of oolitic limestone that is at or very near the surface. Solution holes occasionally form where the surface limestone is dissolved by organic acids. In pine rocklands, there is typically very little soil development, consisting primarily of accumulations of low-nutrient sand, marl, clayey loam, and organic debris found in solution holes, depressions, and crevices on the limestone surface (FNAI 2010a, p. 62). However, extensive sandy pockets can be found at the northern end of the Miami Rock Ridge, beginning from approximately North Miami Beach and extending south to approximately SW 216 Street (which runs east-west approximately one-half mile south of Quail Roost Pineland) (Service 1999, p. 3-162). Rockland hammock occurs on a thin layer of highly organic soil covering limestone on high ground that does not regularly flood (FNAI 2010b p. 1). In coastal berms, deep, calcareous sandy soils are the typical substrate of this habitat.

These substrates provide anchoring, nutrients, moisture regime, and suitable soil chemistry for Blodgett's silverbush; and facilitate a community of associated plant species that create a competitive regime that allows Blodgett's silverbush to persist and spread. Therefore, based on the information above, we identify substrates derived from calcareous limestone (often exposed with little soil development in pine rocklands; with a thin to thick organic soil layer in the case of rockland hammocks; deep, calcareous soils in coastal berm) that provide nutritional requirements and suitable growing conditions (
e.g.,
pH, nutrients, anchoring and drainage) to be an essential physical feature for Blodgett's silverbush.

Cover or Shelter

As previously mentioned, Blodgett's silverbush occurs in pine rockland, rockland hammock, and coastal berm habitats in the lower Florida Keys in Monroe County and the Miami Rock Ridge in Miami-Dade County; and adjacent disturbed areas (Bradley and Gann, 1999, p. 3). Pine rocklands of the Florida Keys are characterized by an open canopy of South Florida slash pine. The shrub/understory layer is also characteristically open, although the height and density of the shrub layer varies based on fire frequency, with understory plants growing taller and denser as time since fire increases. The open canopy and understory of pine rocklands are required to allow sufficient sunlight to reach the herbaceous layer and permit growth and flowering of Blodgett's silverbush (Ross and Ruiz 1996, pp. 5-6; Bradley and Saha 2009, p.4).

Rockland hammock forest floor is largely covered by leaf litter and may have an organic soil layer of variable depth. Rockland hammocks typically have larger, more mature trees and deep organic soil layer in the interior, while the margins can be almost impenetrable in places with dense growth of smaller shrubs, trees, and vines and shallow organic soil layer. Mature hammocks may be open beneath a tall, well-defined canopy and subcanopy. More commonly, in less mature or disturbed hammocks, dense woody vegetation of varying heights from canopy to short shrubs is often present. Herbaceous species are occasionally present and generally sparse in coverage (FNAI 2010b p. 1).

Coastal berm is a short forest or shrub thicket found on long, narrow, storm-deposited ridges (sand dunes). Structure and composition of the vegetation is variable depending on height and time since the last storm event. The most stable berms may share some tree species with rockland hammocks, but generally have a greater proportion of shrubs and herbs. This is a structurally variable community that may appear in various stages of succession following storm disturbance, from scattered herbaceous beach colonizers to a dense stand of tall shrubs (FNAI 2010c, p. 2).

Disturbed areas that are adjacent to pine rocklands, rockland hammocks, and coastal berms that support Blodgett's silverbush may have little to no pine or hardwood canopy, but an herbaceous layer dominated by native herbs and grasses. Usually these are former (remnant) pine rocklands or rockland hammocks that have a history of disturbance (clearing or scraping). These sites tend to be infrequently (every 2-3 months) mowed areas adjacent to existing pine rocklands or rockland hammocks, such as roadsides and fields. These areas provide the open conditions required by Blodgett's silverbush (Bradley 2006, p. 37).

Therefore, based on the information above, we identify vegetation composition and structure characterized by an open canopy and understory that allows for sufficient sunlight, and space for individual growth and population expansion, to be an essential feature for Blodgett's silverbush.

Sites for Breeding, Reproduction, or Rearing (or Development) of Offspring

Little is known about the life history of Blodgett's silverbush, including pollination biology, seed production, or dispersal. Blodgett's silverbush reproduction is sexual, with new plants generated from seeds. This species likely requires insect visitation for pollination, although there is limited information on this.

The pine rocklands, rockland hammocks, coastal berms, and adjacent disturbed habitats identified above as physical or biological features provide a plant community with associated plant species that foster a competitive regime suitable to Blodgett's silverbush and contain adequate open space for the recruitment of new plants. Associated plant species in these habitats attract and provide cover for insect pollinators required for Blodgett's silverbush pollination.

Therefore, based on the information above, we identify pine rockland, rockland hammock, and coastal berm habitat and adjacent disturbed areas containing the presence of native pollinators for natural pollination and reproduction to be an essential feature for Blodgett's silverbush.

Habitats Representative of the Historical, Geographic, and Ecological Distributions of the Species

Blodgett's silverbush continues to occur in habitats that are representative of the species' historical, geographical, and ecological distribution although its range has been reduced. The species is currently found in pine rocklands, rockland hammocks, and coastal berms, and it also occurs in adjacent disturbed areas. As described above, these habitats provide a community of associated plant and animal species that are compatible with Blodgett's silverbush, vegetation structure that provides adequate sunlight levels and open space for plant growth and regeneration, and substrates with adequate moisture availability and suitable soil chemistry. Representative communities are located on Federal, State, local, and private conservation lands that implement conservation measures benefitting the species.

Disturbance Regime

Pine rockland habitat that could or currently support Blodgett's silverbush depend on a disturbance regime of wild or prescribed fire to open the canopy and provide light levels sufficient to support Blodgett's silverbush. The historical frequency and magnitude of fire allowed for the persistence of Blodgett's silverbush, maintaining an open canopy and understory, and preventing succession (transition) of pine rocklands to hardwood-dominated community (rockland hammock). In the absence of fire, some areas of pine rockland may have closed canopies, resulting in areas lacking enough available sunlight to support Blodgett's silverbush. Most of these areas can be restored if habitats are managed with a combination of mechanical hardwood removal and prescribed fire.

Rockland hammock is susceptible to fire, frost, canopy disruption, and ground water reduction. Rockland hammock can be the advanced successional stage of pine rockland, especially in cases where rockland hammock is adjacent to pine rockland. In such cases, when fire is excluded from pine rockland for 15 to 25 years, it can succeed to rockland hammock vegetation. Historically, rockland hammocks in south Florida evolved with fire in the landscape, fire most often extinguished near the edges when it encountered the hammock's moist microclimate and litter layer. However, rockland hammocks are susceptible to damage from fire during extreme drought or when the water table is lowered. In these cases, fire can cause tree mortality and consume the organic soil layer. Rockland hammocks are also sensitive to the strong winds and storm surge associated with hurricanes (FNAI 2010b p. 2).

Coastal berms are deposited by storm waves along low-energy coasts. Their distance inland depends on the height of the storm surge. Coastal berms that are deposited far enough inland and remain undisturbed may in time succeed to hammock. This is a structurally variable community that may appear in various stages of succession following storm disturbance, from scattered herbaceous beach colonizers to a dense stand of tall shrubs (FNAI 2010c, p. 2).

The sparsely vegetated edges or interior portions laid open by canopy disruption are the areas of rockland hammock and coastal berm that have light levels sufficient to support Blodgett's silverbush. However, the dynamic nature of the habitat means that areas not currently open may become open in the future as a result of canopy disruption from hurricanes, while areas currently open may develop denser canopy over time, eventually rendering that portion of the hammock unsuitable for Blodgett's silverbush.

Disturbed sites that support Blodgett's silverbush are typically maintained by infrequent mowing. Mowing is similar in effect to fire in that it limits encroachment of hardwood species and maintains open canopy conditions suitable for Blodgett's silverbush. We consider wildfire to be the natural disturbance factor for pine rocklands. Periodic hurricanes and storm surge are the natural disturbance factors for rockland hammock and coastal berm. In adjacent disturbed areas currently supporting the species, mowing serves some of the ecological function of fire and maintains suitable habitat conditions (open canopy) for the species.

Therefore, based on the information above, we identify periodic natural (
e.g.,
fire, hurricanes) or nonnatural (
e.g.,
prescribed fire, mowing) disturbance regimes that maintain open canopy conditions to be essential features for Blodgett's silverbush.

Summary of Physical or Biological Features Essential to the Conservation of Blodgett's Silverbush

Based on the best available science related to the life history and ecology of the species, as outlined in the discussion above, we have determined that the following physical or biological features are essential to the conservation of Blodgett's silverbush:

South Florida pine rockland, rockland hammock, or coastal berm habitats and adjacent disturbed areas:

(1) Consisting of limestone substrate that provides nutritional requirements and suitable growing conditions (
e.g.,
pH, nutrients, anchoring and drainage);

(2) Characterized by an open canopy and understory with a high proportion of native plant species to provide for sufficient sunlight to permit growth and flowering;

(3) Subjected to a monthly mean temperature characteristic of the subtropical humid classification in Miami-Dade County and tropical humid classification in Monroe County in every month of the year, with short hydroperiods ranging of up to 60 days each year;

(4) Subjected to periodic natural (
e.g.,
fire, hurricanes, storm surge) or nonnatural (
e.g.,
prescribed fire, mowing) disturbance regimes to maintain open canopy conditions; and

(5) Containing the presence of native pollinators for natural pollination and reproduction.

Special Management Considerations or Protection

When designating critical habitat, we assess whether the specific areas within the geographical area occupied by the species at the time of listing contain features which are essential to the conservation of the species and which may require special management considerations or protection. The features essential to the conservation of Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush may require special management considerations or protection to reduce threats related to habitat loss, fragmentation, and modification primarily due to development; inadequate fire management; nonnative plants; hurricanes and storm surge; changes in disturbance regime; and sea level rise. For an in-depth discussion of threats, see Summary of Factors Affecting the Species in our September 29, 2015, proposed listing rule (80 FR 58536) and September 29, 2016, final listing rule (81 FR 66842).

Some of these threats (
e.g.,
habitat loss, inadequate fire management) can be addressed by special management considerations or protection while others (
e.g.,
sea level rise, hurricanes, storm surge) may be beyond the control of landowners and managers. However, even when landowners or land managers may not be able to control all the threats, they may be able to address or ameliorate the effects of the threats. Habitat loss is a primary threat to Big Pine partridge pea, wedge spurge, sand

flax, and Blodgett's silverbush. Loss of pine rocklands, rockland hammock, and coastal berm to development has reduced these habitats in Monroe and Miami-Dade Counties.

Habitat fragmentation can have negative effects on populations, especially rare plants, and can affect survival and recovery (Aguilar et al. 2006, pp. 968-980; Aguilar et al. 2008, pp. 5177-5188; Potts et al. 2010, pp. 345-352). In general, habitat fragmentation causes habitat loss, habitat degradation, habitat isolation, changes in species composition, changes in species interactions, increased edge effects, and reduced habitat connectivity (Fahrig 2003, pp. 487-515; Fischer and Lindenmayer 2007, pp. 265-280). Habitat fragments are often functionally smaller than they appear because edge effects (such as increased nonnative, invasive species or wind speeds) impact the available habitat within the fragment (Lienert and Fischer 2003, p. 597). For example, decreases in Big Pine partridge pea seed production near urban areas due to increased seed predation, compared with areas away from development have been reported (Liu and Koptur 2003, p. 1184).

Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush occur on a mix of private and publicly owned lands, most of which are managed for conservation. Populations that occur on private land or non-conservation public land are vulnerable to habitat loss, while populations on conservation lands are vulnerable to the effects of habitat degradation if disturbance regimes are disrupted (
e.g.,
through inadequate fire management or change in management practices on disturbed sites that support the species). Prolonged lack of fire in pine rockland typically results in succession to rockland hammock, and displacement of native species by invasive, nonnative plants often occurs. Changes in management practices at disturbed sites may include changes in mowing frequency or height, herbicide use, deposition of fill material, and sodding. Further development and degradation of pine rockland, rockland hammock, and coastal berm increase fragmentation and decrease the conservation value of the remaining functioning habitats. In addition, pine rocklands are expected to be further degraded and fragmented due to anticipated sea level rise, which would fully or partially inundate most pine rocklands and increase salinity of the water table and soils. These impacts are likely to cause vegetation shifts in additional pine rocklands, particularly in the lower Florida Keys. Some existing pine rockland, rockland hammock, and coastal berm areas are also projected to be developed for housing as the human population grows and adjusts to rising sea levels.

In summary, the features essential to the conservation of Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush may require special management considerations or protection to reduce threats and conserve these features. Actions that could ameliorate threats include, but are not limited to:

(1) Increase habitat restoration and management efforts, including fire management and nonnative plant control;

(2) Protect, restore, or enhance inland or higher elevation habitats where these species occur and are predicted to be unaffected or less affected by sea level rise;

(3) Augment existing small populations; and

(4) Conduct annual or seasonal monitoring efforts, or monitoring conducted prior to, but coordinated with habitat and fire management planning to refine management efforts over time.

Criteria Used To Identify Critical Habitat

As required by section 4(b)(2) of the Act, we use the best scientific data available to designate critical habitat. In accordance with the Act and our implementing regulations at 50 CFR 424.12(b), we review available information pertaining to the habitat requirements of the species and identify specific areas within the geographical area occupied by the species at the time of listing and any specific areas outside the geographical area occupied by the species to be considered for designation as critical habitat.

We are proposing to designate critical habitat in areas within the geographical area occupied by these species at the time of listing in 2016. At this time, we have not identified specific areas outside the geographical range occupied by the species that are essential for the species' conservation. However, as discussed below, we are considering whether areas outside the geographical range of the Big Pine Partridge Pea, wedge spurge, and sand flax at the time of listing meet the definition of critical habitat. If we determine some or all of those areas are critical habitat for these species, we will include them in our final designation.

We anticipate that full recovery for Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush will require continued protection of the remaining extant populations and habitat and augmenting existing small populations. Recovery of Big Pine partridge pea, wedge spurge, and sand flax may also require reestablishing populations in additional areas (
i.e.,
unoccupied areas) to approximate more closely the species' historical distribution to ensure adequate numbers of plants exist in stable populations and these populations occur over their entire geographic range. This scenario could help to reduce the chance that catastrophic events, such as storms, will simultaneously affect all known populations. However, some of the historical locations no longer contain suitable habitat, and thus are not proposed.

Small plant populations or those with limited distributions, such as Big Pine partridge pea, wedge spurge, and sand flax, are vulnerable to relatively minor environmental disturbances (Frankham 2005, pp. 135-136) that could result in the loss of genetic diversity from genetic drift, the random loss of genes, and inbreeding (Ellstrand and Elam 1993, pp. 217-237; Leimu et al. 2006, pp. 942-952). Plant populations with lowered genetic diversity are more prone to local extinction (Barrett and Kohn 1991, pp. 4, 28). Smaller plant populations generally have lower genetic diversity, and lower genetic diversity may in turn lead to even smaller populations by decreasing the species' ability to adapt, thereby increasing the probability of population extinction (Newman and Pilson 1997, p. 360; Palstra and Ruzzante 2008, pp. 3428-3447). Because of the dangers associated with small populations or limited distributions, the recovery of many rare plant species, such as Big Pine partridge pea, wedge spurge, and sand flax, may include the creation of new sites or reintroductions to ameliorate these effects.

In considering our proposal of critical habitat, we identified the following conservation strategy and goals for Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush:

(1) Conserve existing viable populations with sufficient native habitat;

(2) Work with partners to conserve existing populations, and implement efforts that will benefit the species and its habitat; and

(3) Augment existing populations and facilitate establishment/reestablishment of populations into suitable protected habitat.

To facilitate the application of our conservation strategy and goals for these species, we utilized the Shaffer and Stein (2000, entire) methodology for

conserving the resiliency, representation, and redundancy of imperiled species. Resiliency is the ability to sustain populations through the natural range of favorable and unfavorable conditions. Representation ensures adaptive capacity within a species and allows it to respond to environmental changes. This can be facilitated by conserving not just genetic diversity, but also the species' associated habitat type and plant communities. Redundancy ensures an adequate number of sites with resilient populations such that the species has the ability to withstand catastrophic events. Implementation of this methodology has been widely accepted as a reasonable conservation strategy (Tear et al. 2005, p. 841).

Big Pine Partridge Pea

Big Pine partridge pea is endemic to the lower Florida Keys in Monroe County, Florida. Historical records exist for occurrences in pine rocklands on five islands: Big Pine Key, Ramrod Key, Cudjoe Key, No Name Key, and Lower Sugarloaf Key (Hodges and Bradley 2006, pp. 20-21). At the time of listing and currently, native populations of the plant occur only on Big Pine Key and Cudjoe Key since the species has been extirpated from Ramrod Key and Lower Sugarloaf Key (Bradley and Gann 1999, p. 18; Hodges and Bradley 2006, p. 21; Lange et al. 2019). In 2019, a population was successfully introduced in NKDR on No Name Key. Except for Ramrod Key, all these Keys still contain pine rockland habitat. While the Big Pine Key population is relatively large, estimated at 313,914 plants in 2013 (Bradley et al. 2015, p. 21), the Cudjoe Key population was relatively small, consisting of approximately 150 individuals ((Hodges and Bradley 2006, p. 21), and recent surveys did not find the species there (Lange et al. 2019, p. 16). Therefore, if the species is not found at Cudjoe Key during future surveys, reintroductions may be needed at Cudjoe Key.

Given the species occurs only within the lower Florida Keys, it has inherently low redundancy; with only two extant populations at the time of listing, the current redundancy of native populations has been even further reduced from historical levels. In addition, because there currently are three populations (two native and one reintroduced) across the naturally limited historical range of the species, Big Pine partridge pea is vulnerable to stochastic extinction events from natural or other disturbances (such as hurricanes or storm surge) that could affect the entire geographic range of the species. Both natural populations occur on small islands where the amount of suitable remaining habitat is limited (low resiliency), and much of the remaining habitat may be lost to sea level rise over the next century. Therefore, we are proposing critical habitat units that contain the physical or biological features essential to the conservation of the species and that support both extant populations at the time of listing.

Additionally, we acknowledge that areas unoccupied at the time of listing may be essential for the conservation of the Big Pine partridge pea. We are considering whether areas of remaining pine rockland habitat on Little Pine Key, No Name Key, and Sugarloaf Keys meet the definition of critical habitat. The area on Little Pine Key consists of approximately 97 ac (39 ha) of pine rockland habitat in Monroe County and is comprised entirely of lands in Federal ownership, 100 percent of which are located within NKDR. Pine rocklands cover about two-thirds of the interior portion of the island. We note that this area wholly overlaps with designated critical habitat for silver rice rat and Bartram's scrub-hairstreak butterfly. The area on No Name Key includes approximately 123 ac (50 ha) of pine rockland habitat in Monroe County comprised of a combination of Federal lands within NKDR, State lands, County lands, and property in private or other ownership). State lands are interspersed within NKDR lands and managed as part of the Refuge. We note that this area wholly overlaps with designated critical habitat for Bartram's scrub-hairstreak butterfly. Finally, on Sugarloaf Keys, we are considering approximately 73 ac (30 ha) of pine rockland habitat north of U.S. 1, comprised of a combination of Federal lands within NKDR, County lands, and property in private or other ownership. We note that these areas on Sugarloaf Keys wholly overlap with the areas being proposed as critical habitat for the sand flax and the endangered key deer occurs throughout this area. We will determine whether these areas are essential to protect habitat needed to recover the species and establish new populations within the range of the species such that they meet the definition of critical habitat. If we decide some or all of these areas are essential to the conservation of the Big Pine partridge pea, we will include them in our final critical habitat determination (see also Information Requested, above).

Wedge Spurge

Wedge spurge is endemic to the lower Florida Keys in Monroe County, Florida. Its historical range encompassed pine rocklands on Big Pine Key. At the time of listing and currently, the only native population of the plant currently occurs on Big Pine Key, with small groups of plants scattered widely across the island. The Big Pine population is relatively large, estimated at 368,557 individuals in 2014 (Bradley et al. 2015, pp. 24-25); the presence of this population was verified in 2019 (Lange et al. 2019, p. 16). However, since the time the species was listed, a population was successfully introduced in NKDR on No Name Key. While the Big Pine Key population is relatively large, estimated at 368,557 individuals in 2014 (Bradley et al. 2015, pp. 24-25), it is the only extant native population.

Given the species occurs within the lower Florida Keys, it has inherently low redundancy; with only one extant populations at the time of listing, the current redundancy of native population has been reduced from historical levels. Because there currently are only two populations (one native and one introduced) across the naturally limited historical range, wedge spurge is vulnerable to stochastic extinction events from natural or other disturbances (such as hurricanes or storm surge) that could affect the entire geographic range of wedge spurge. The sole natural population occurs on a small island where the amount of suitable habitat is limited (low resiliency) and much of that habitat may be lost to sea level rise over the next century. Therefore, the resiliency of the population and redundancy of the wedge spurge will continue to be limited by the amount of pine rockland habitat remaining in the lower Florida Keys. We are proposing a critical habitat unit that contains the physical or biological features essential to the conservation of the species and supports the single native population on Big Pine Key extant at the time of listing.

Additionally, we acknowledge that areas unoccupied at the time of listing may be essential for the conservation of the wedge spurge. We are considering whether areas of remaining pine rockland habitat on Little Pine Key, No Name Key, Cudjoe Key, and Sugarloaf Keys of the wedge spurge meet the definition of critical habitat. The area on Little Pine Key consists of approximately 97 ac (39 ha) of pine rockland habitat in Monroe County and is comprised entirely of lands in Federal ownership, 100 percent of which are located within NKDR. Pine rocklands cover about two-thirds of the interior portion of the island. We note that this area wholly overlaps with designated critical habitat for silver rice rat and

Bartram's scrub-hairstreak butterfly. The area on No Name Key includes approximately 123 ac (50 ha) of pine rockland habitat in Monroe County comprised of a combination of Federal lands within NKDR, State lands, County lands, and property in private or other ownership. State lands are interspersed within NKDR lands and managed as part of the Refuge. We note that this area wholly overlaps with designated critical habitat for Bartram's scrub-hairstreak butterfly. The area on Cudjoe Key consists of approximately 88 ac (33 ha) of pine rockland habitat in Monroe County and is comprised of a combination of Federal lands within NKDR, State lands, County lands, and property in private or other ownership. State lands are interspersed within NKDR lands and managed as part of the Refuge. We note that this area wholly overlaps with designated critical habitat for silver rice rat. Finally, on Sugarloaf Keys, we are considering approximately 73 ac (30 ha) of pine rockland habitat north of U.S. 1, comprised of a combination of Federal lands within NKDR, County lands, and property in private or other ownership. We note that these areas on Sugarloaf Keys wholly overlap with the areas being proposed as critical habitat for the sand flax and the endangered key deer occurs throughout this area. We will determine whether these areas are essential to protect habitat needed to recover the species and establish new populations within the range of the species such that they meet the definition of critical habitat. If we decide some or all of these areas are essential for the conservation of the wedge spurge, we will include them in our final critical habitat determination (see also Information Requested, above).

Sand Flax

Sand flax has a historical range consisting of central and southern Miami-Dade County and Monroe County in the lower Florida Keys (Bradley and Gann 1999, p. 61). At the time of listing and currently, there were twelve extant populations of sand flax, with eight extant populations in Miami-Dade County and four extant populations in the Florida Keys. In Miami-Dade County, historical records for the species were widespread from the Coconut Grove area to the southern part of the county, close to what is now the main entrance to ENP and Turkey Point (Bradley and Gann 1999, p. 61). In 2013, sand flax populations were found at six sites, containing an estimated total of 107,060 plants (Bradley and van der Heiden 2013, p. 4). In Miami-Dade County, recent observations include confirmation of the species' continued presence at the Richmond Pinelands, Martinez Pineland Preserve, Department of Defense (DoD) Special Operations Command South (SOCSO) and Homestead Air Reserve Base (HARB), and the C-102 and L-31E canal levee populations. Additionally, a new population was established at Rockdale Pineland in 2019 (Possley, pers. comm. 2019). The four largest populations of sand flax include Homestead, Florida (located on the HARB and SOCSO DoD sites), estimated at 96,037 individuals; the C-102 canal levee and L-31E canal levee sites, estimated at 1,000 to 10,000 plants, respectively; and Big Pine Key, estimated at 2,676 individuals. All other sites have fewer than 100 individuals, except Martinez pinelands (100-200 individuals) and Lower Sugarloaf Key (531 individuals). Two populations occupy levees that cannot be restored to pine rockland habitat, rendering sand flax vulnerable to stochastic extinction events from natural or other disturbances (such as hurricanes or storm surge) that could affect the entire geographic range of sand flax.

In the Florida Keys (Monroe County), there are historical records of the species from Big Pine Key, Ramrod Key, Upper and Lower Sugarloaf Keys, Park Key, Boca Chica Key, Middle Torch Key (Bradley and Gann 1999, p. 61), and Big Torch Key (Hodges 2010, p. 10). The current distribution of sand flax includes four islands: Big Pine Key, Upper and Lower Sugarloaf Keys, and Big Torch Key. Additionally, a population was successfully introduced in NKDR on No Name Key since the time of listing.

Resiliency of sand flax will continue to be limited by the reduced amount of pine rockland habitat remaining in Florida. All Miami-Dade populations are on small remnant pine rockland sites and adjacent disturbed areas, while all Monroe County populations occur on small islands. In both cases, the amount of suitable remaining habitat is limited (low resiliency) and much of the remaining habitat may be lost to sea level rise over the next century. Therefore, we are proposing critical habitat units that contain the physical or biological features essential to the conservation of the species and support the seven extant populations at the time of listing.

Additionally, we acknowledge that areas unoccupied at the time of listing may be essential for the conservation of the sand flax. We are considering whether areas of remaining pine rockland habitat on Little Pine Key, No Name Key, Cudjoe Key, and Sugarloaf Keys of the wedge spurge meet the definition of critical habitat. The area on Little Pine Key consists of approximately 97 ac (39 ha) of pine rockland habitat in Monroe County and is comprised entirely of lands in Federal ownership, 100 percent of which are located within NKDR. Pine rocklands cover about two-thirds of the interior portion of the island. We note that this area wholly overlaps with designated critical habitat for silver rice rat and Bartram's scrub-hairstreak butterfly. The area on No Name Key includes approximately 123 ac (50 ha) of pine rockland habitat in Monroe County comprised of a combination of Federal lands within NKDR, State lands, County lands, and property in private or other ownership. State lands are interspersed within NKDR lands and managed as part of the Refuge. We note that this area wholly overlaps with designated critical habitat for Bartram's scrub-hairstreak butterfly. The area on Cudjoe Key consists of approximately 88 ac (33 ha) of pine rockland habitat in Monroe County and is comprised of a combination of Federal lands within NKDR, State lands, County lands, and property in private or other ownership. State lands are interspersed within NKDR lands and managed as part of the Refuge. We note that this area wholly overlaps with designated critical habitat for silver rice rat. The area of Trinity Pinelands consists of approximately 48 ac (19 ha) of pine rockland habitat in Miami-Dade County and is comprised of a combination of State lands, County lands, and property in private or other ownership. We note that this area wholly overlaps with designated critical habitat for Carter's small-flowered flax (
Linum carteri var. carteri
) and Florida brickell-bush. The area of Nixon Smiley consists of approximately 264 ac (107 ha) of pine rockland habitat in Miami-Dade County comprised of a combination of State lands, County lands, and property in private or other ownership. We note that this area wholly overlaps with designated critical habitat for Carter's small-flowered flax and Florida brickell-bush. The area of U.S. Department of Agriculture (USDA) Subtropical Horticulture Research Station consists of approximately 297 ac (120 ha) of pine rockland habitat in Miami-Dade County and is comprised of a combination of Federal lands, State lands, and property in private or other ownership. We note that this area wholly overlaps with designated critical habitat for Carter's small-flowered flax and Florida brickell-bush. The area of Quail's Roost consists of approximately 256 ac (104 ha) of pine rockland habitat in Miami-Dade County and is comprised

of a combination of State lands, County lands, and property in private or other ownership. We note that this area wholly overlaps with designated critical habitat for Carter's small-flowered flax, Florida brickell-bush, and Bartram's scrub hairstreak butterfly. The area of Navy Wells consists of approximately 558 ac (226 ha) of pine rockland habitat in Miami-Dade County and is comprised of a combination of State lands, County lands, and property in private or other ownership. We note that this area wholly overlaps with designated critical habitat for Carter's small-flowered flax, Florida brickell-bush, Bartram's scrub hairstreak butterfly, and Florida leafwing butterfly. We will determine whether these areas are essential to protect habitat needed to recover the species and establish new populations within the range of the species such that they meet the definition of critical habitat. If we decide some or all of these areas are essential for the conservation of the wedge spurge, we will include them in our final critical habitat determination (see also Information Requested, above).

Blodgett's Silverbush

Blodgett's silverbush historically occurred from central and southern Miami-Dade County from Brickell Hammock to Long Pine Key in ENP, and in Monroe County throughout the Florida Keys (Monroe County) from Totten Key south to Key West (Bradley and Gann 1999, p. 2). At the time of listing and currently, the Blodgett's silverbush consists of 20 extant populations in Miami-Dade County and Monroe County in the Florida Keys. Blodgett's silverbush is currently known from central Miami-Dade County from Coral Gables and southern Miami-Dade County to Long Pine Key in ENP, and from nine islands in the Florida Keys, from Windley Key (Bradley and Gann 1999, p. 3) southwest to Boca Chica Key (Hodges and Bradley 2006, pp. 10, 43). At least eight of the 20 extant populations of Blodgett's silverbush consist of fewer than 100 individuals. These small populations are at risk of adverse effects from reduced genetic variation, an increased risk of inbreeding depression, and reduced reproductive output. Many of these populations are small and isolated from each other, decreasing the likelihood that they could be naturally reestablished if extinction from one location occurred.

Resiliency will continue to be limited by the reduced amount of pine rockland, rockland hammock, and coastal habitat remaining in Miami-Dade and Monroe Counties. All Miami-Dade County populations are on small remnant pine rockland, rockland hammock, and coastal berm sites and adjacent disturbed areas, while all Monroe County populations occur on small islands. In both cases, the amount of suitable remaining habitat is limited (low resiliency) and much of the remaining habitat may be lost to sea level rise over the next century. Therefore, we are proposing to designate critical habitat units within the historical range of Blodgett's silverbush and that contain the physical or biological features essential to the conservation of the species, where the species was extant at the time of listing.

The amount and distribution of critical habitat being proposed for designation would allow existing (native) populations of Blodgett's silverbush to:

(1) Maintain their existing distribution;

(2) Expand their distribution into suitable nearby areas (needed to offset habitat loss and fragmentation);

(3) Use habitat depending on habitat availability (response to changing nature of coastal habitat including sea level rise) and support genetic diversity;

(4) Increase the size of each population to a level where the threats of genetic, demographic, and normal environmental uncertainties are diminished; and

(5) Maintain their ability to withstand local or unit-level environmental fluctuations or catastrophes.

Sources of Data to Identify Critical Habitat Boundaries

We have determined that all areas known to be occupied at the time of listing should be proposed for critical habitat designation because all occupied sites are necessary to conserve the species. To determine the location and boundaries of occupied critical habitat, the Service used sources of data and information for Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush that include the following:

(1) Species occurrence spatial data and ArcGIS geographic information system software to spatially depict the location and extent of documented populations of the species;

(2) Reports prepared by FNAI, Fairchild Tropical Botanical Garden, Institute for Regional Conservation, National Park Service, and Florida Department of Environmental Protection;

(3) Historical records found in reports and associated voucher specimens housed at herbaria, all of which are referenced in the above-mentioned reports;

(4) Digitally produced habitat maps provided by Miami-Dade and Monroe Counties; and

(5) Aerial images of Miami-Dade and Monroe Counties. The presence of pine rocklands was determined through the use of GIS spatial data depicting the current habitat status. These habitat data for the Florida Keys were developed by Monroe County from 2006 aerial images, and ground conditions for many areas were checked in 2009. Habitat data from Monroe County identifies pine rockland habitat. Habitat data for Miami-Dade County were developed by Miami-Dade Department of Environmental Protection for the Natural Forest Community program and include pine rocklands and rockland hammocks. Pine rockland, rockland hammock, and coastal berm habitat follow predictable landscape patterns and have a recognizable signature in the aerial imagery. Aerial imagery was utilized to identify disturbed areas adjacent to pine rocklands, rockland hammock, and coastal berm.

We delineated critical habitat unit boundaries for these species using the following criteria:

(1) The delineation included space to allow for the successional nature of the habitats (
i.e.,
gain and loss of areas with sufficient light availability due to disturbance of the vegetation, driven by natural events such as inundation and hurricanes, or through natural or prescribed fire) and habitat transition or loss due to sea level rise.

(2) All areas (
i.e.,
physical or biological features) will require special management to be able to support a higher density of plants within the occupied space. These areas generally are habitats where some of the habitat features have been degraded or lost through natural or human causes. These areas would help to offset the anticipated loss and degradation of habitat occurring or expected from the effects of climate change (such as sea level rise) or development.

(3) The areal extent of a plant population is dynamic over time within suitable habitat, while a survey represents a snapshot in time. Unsurveyed areas near mapped populations likely support plants currently or did in the past.

Areas Occupied at the Time of Listing

The proposed occupied critical habitat designation for Big Pine partridge pea, wedge spurge, sand flax, and Blodgett's silverbush focuses on areas within the historical range that have retained the necessary habitat characteristics that will allow for the maintenance and expansion of existing

populations, and the establishment or reestablishment of populations through reintroduction (
i.e.,
Cudjoe Key for Big Pine partridge pea). The proposed occupied critical habitat units were delineated based on documented extant populations at the time of listing. These units include the mapped extent of the population and nearby areas that contain one or more of the physical or biological features essential to the conservation of the species.

In summary, for areas within the geographic area occupied by Big Pine partridge pea, wedge spurge, and sand flax at the time of listing, we delineated critical habitat unit boundaries using the following criteria:

(1) Pine rockland habitat that was occupied by the species at the time of listing;

(2) Presence of suitable pine rockland habitat and sufficient essential features; and

(3) Whether the pine rockland habitat is natural versus human-made habitat that was not historically pine rockland.

For Big Pine partridge pea, two occupied units (Big Pine Key and Cudjoe Key) are proposed as critical habitat. We consider pine rockland to be the primary habitat for Big Pine partridge pea. Adjacent disturbed areas currently supporting the species are also considered essential when adjacent pine rocklands do not support an existing population or are of insufficient size or connectivity to support a population of the species. While pine rockland habitat occurs on numerous other Keys, including nearby Sugarloaf Keys and Little Pine Key, none support existing populations of Big Pine partridge pea now nor did they at the time of listing. As mentioned previously, after the time of listing, a population of Big Pine partridge pea was introduced on No Name Key, which has high-quality pine rockland habitat and currently supports the reintroduced population. Plants and seeds were introduced in 2019 by Fairchild Tropical Botanical Garden, in cooperation with NKDR and the Florida Department of Agriculture and Consumer Services. This action aligns with the recovery strategy that the Service will seek to implement for this species. We are considering whether areas on these Keys may be essential for the conservation of the Big Pine partridge pea. If we determine they are, they will be included in our final designation.

For wedge spurge, one unit (one population: Big Pine Key) is proposed as critical habitat. We consider pine rockland to be the primary habitat for wedge spurge. Adjacent disturbed areas currently supporting the species are also considered essential when adjacent pine rocklands do not support an existing population or are of insufficient size or connectivity to support a population of the species. Even though pine rockland habitat is present on numerous other Keys, including nearby Little Pine Key, Cudjoe Key, and Sugarloaf Keys, none support existing populations of the species now, nor did they at the time of listing or historically. As mentioned previously, after the time of listing, a population of wedge spurge was introduced on No Name Key. We are considering whether areas on these Keys may be essential for the conservation of the wedge spur. If we determine they are, they will be included in our final designation.

For sand flax, five units containing seven populations are proposed for critical habitat. We consider pine rockland to be the primary habitat for sand flax. While pine rockland habitat occurs on numerous other keys in Monroe County and other areas in Miami-Dade County, these do not support existing populations of sand flax now, nor did they historically or at the time of listing, and are therefore not proposed as critical habitat. Adjacent disturbed areas currently supporting the species are also considered essential when adjacent pine rocklands do not support an existing population or are of insufficient size or connectivity to support a population of sand flax. Such is the case for the area we are proposing as critical habitat on Sugarloaf Key (see below).

Two well-maintained levees in Miami-Dade County support large populations of sand flax, which were established when fill used to construct the levees included pine rockland substrate and the seeds of pine rockland species, such as sand flax. While these levees support robust populations of sand flax, they are not included in proposed critical habitat because the habitat is human-made, and these populations are not natural populations or purposefully established. In addition, we do not expect these areas to support the needs of the species long-term, as the maintenance of these areas may not be compatible with the species over time. In addition, there are roadside areas on Middle Torch Key, Big Torch Key, and Lower Sugarloaf Keys that support sand flax, but are not associated with an adjacent pine rockland. These populations may also have been established at these sites through the deposition of fill. Because these areas are mowed occasionally, they provide the open conditions required by sand flax (Bradley 2006, p. 37). However, these areas are not included in proposed critical habitat, because the habitat is human-made, do not contain the physical or biological features (
i.e.,
these disturbed areas are not adjacent to native pine rockland and are not characterized by an open canopy and understory with a high proportion of native plant species occurring in pine rockland habitat), and they are not adjacent to pine rockland that would facilitate expansion of the population into natural habitat.

As mentioned previously, there is remaining pine rockland habitat on numerous other Keys, including Little Pine Key and Cudjoe Key, and areas in Miami-Dade County, including Trinity Pinelands, Nixon Smiley, Quail's Roost, Navy Wells, and USDA Horticulture Research Station, but these areas do not currently or at the time of listing support existing populations of sand flax. No Name Key currently supports a reintroduced populations of sand flax in NKDR. We are considering whether these areas may be essential for the conservation of the sand flax. If so, we will include them in our final designation.

For Blodgett's silverbush, for areas within the geographic area occupied at the time of listing, we delineated critical habitat unit boundaries using the following criteria:

(1) Pine rockland, rockland hammock, and coastal berm habitats that were occupied by Blodgett's silverbush at the time of listing;

(2) Presence of suitable pine rockland, rockland hammock, and coastal berm habitats and sufficient essential features; and

(3) Whether the pine rockland, rockland hammock, and coastal berm habitats are natural versus human-made habitat that was not historically pine rockland, rockland hammock, or coastal berm.

For Blodgett's silverbush, 13 occupied units contain 18 populations are proposed as critical habitat for the species. We consider pine rockland to be one of the primary habitats for Blodgett's silverbush. In addition, we consider rockland hammock and coastal berm to be primary habitats for the species. Adjacent disturbed areas currently supporting the species are also considered essential when adjacent pine rocklands, rockland hammocks, or coastal berms do not support an existing population or are of insufficient size or connectivity to support a population of sand flax. While pine rockland habitat, rockland hammock, and coastal berm occurs on numerous other Keys and areas in Miami-Dade County, these do not support existing populations of Blodgett's silverbush now, nor did they

historically or at the time of listing, and therefore, are not proposed as critical habitat. We have not identified any specific areas outside the geographical area occupied by the species at the time it was listed that are essential for the conservation of the species. Accordingly, we are not proposing any unoccupied areas as critical habitat.

In summary, for areas within the geographical area occupied by Big Pine partridge pea, wedge spurge, and sand flax at the time of listing, we delineated critical habitat unit boundaries by evaluating habitat suitability of pine rockland habitat within the historical range of the plant and retained those areas that contain some or all of the physical or biological features essential to the conservation of the species and that may require special management. For areas within the geographical area occupied by Blodgett's silverbush at the time of listing, we delineated critical habitat unit boundaries by evaluating habitat suitability of pine rockland, rockland hammocks, and coastal berm habitats within the historical range of the plant and retained those areas that contain some or all of the physical or biological essential to the conservation of the species and that may require special management.

When determining proposed critical habitat boundaries, we made every effort to avoid including developed areas such as lands covered by buildings, pavement, and other structures because such lands lack physical or biological features essential to the conservation of these species, nor are they essential to the conservation of the species themselves. The scale of the maps we prepared under the parameters for publication within the Code of Federal Regulations may not reflect the exclusion of such developed lands. Any such lands inadvertently left inside critical habitat boundaries shown on the maps of this proposed rule have been excluded by text in the proposed rule and are not proposed for designation as critical habitat. Therefore, if the critical habitat is finalized as proposed, a Federal action involving these lands would not trigger section 7 consultation with respect to critical habitat and the requirement of no adverse modification unless the specific action would affect the physical or biological features in the adjacent critical habitat.

We are proposing for designation as critical habitat those lands that we have determined were occupied at the time of listing and which contain one or more of the physical or biological features that are essential to support life-history processes of the species. For Big Pine partridge pea, two units are proposed for designation based on one or more of the physical or biological features being present to support the specie's life-history processes. Both units contain all of the identified physical or biological features and support multiple life-history processes. For wedge spurge, one unit is proposed for designation based on one or more of the physical or biological features being present to support wedge spurge's life-history processes. The unit contains all of the identified physical or biological features and supports multiple life-history processes. For sand flax, five units are proposed for designation based on one or more of the physical or biological features being present to support sand flax's life-history processes. Some units contain all of the identified physical or biological features and support multiple life-history processes. Some units contain only some of the physical or biological features necessary to support sand flax particular use of that habitat. For Blodgett's silverbush, 13 units are proposed for designation based on one or more of the physical or biological features being present to support Blodgett's silverbush's life-history processes. Some units contain all of the identified physical or biological features and support multiple life-history processes. Some units contain only some of the physical or biological features necessary to support Blodgett's silverbush's particular use of that habitat.

The proposed critical habitat designation is defined by the map or maps, as modified by any accompanying regulatory text, presented at the end of this document under Proposed Regulation Promulgation. We include more detailed information on the boundaries of the proposed critical habitat designation in the preamble of this document. We will make the coordinates or plot points or both on which each map is based available to the public on
https://www.regulations.gov
at Docket No. FWS-R4-ES-2022-0116, on our internet site at
https://www.fws.gov/office/florida-ecological-services/library
and at the field office responsible for the designation (see
FOR FURTHER INFORMATION CONTACT
above).

Proposed Critical Habitat Designation for Big Pine Partridge Pea

We are proposing to designate approximately 1,462 ac (592 ha) in two units as critical habitat for Big Pine partridge pea. The critical habitat areas we describe below constitute our current best assessment of areas that meet the definition of critical habitat for Big Pine partridge pea. The two areas we propose as critical habitat are:

(1) BPP1—Big Pine Key, Monroe County, Florida, and

(2) BPP2—Cudjoe Key in Monroe County, Florida.

Land ownership within the proposed critical habitat consists of Federal (67 percent), State (16 percent), County (10 percent), and private and other (7 percent). Other lands include areas for which ownership information is unclear or unavailable. Table 1 shows each critical habitat unit by area, land ownership, and occupancy.

Table 1—Proposed Critical Habitat Units for Big Pine Partridge Pea
[Includes total area, area by land ownership, and occupancy. All areas rounded to the nearest whole acre (ac) and hectare (ha)]

Critical habitat unit

Total ac
(ha)

Federal ac
(ha)

State ac
(ha)

County ac
(ha)

Private/other ac
(ha)

BPP1—Big Pine Key
1,379 (558)
912 (369)
228 (92)
144 (58)
96 (39)

BPP2—Cudjoe Key
83 (33)
66 (27)
3 (1)
1 (0.5)
12 (5)

Total
1,462 (592)
978 (396)
231 (93)
145 (59)
108 (44)

Percent of Total

67%
16%
10%
7%

Note:
Area sizes may not sum due to rounding or minor mapping discrepancies. Both units are occupied by the species.

Nearly all the lands (99.7 percent; all except approximately 4 ac (2 ha)) contained within units proposed as critical habitat for Big Pine partridge pea are designated critical habitat for other federally listed species.

We present brief descriptions of each proposed critical habitat unit and the justification for why each meets the definition of critical habitat for Big Pine partridge pea, below.

Unit BPP1: Big Pine Key, Monroe County, Florida

Unit BPP1 consists of 1,379 ac (558 ha) in Monroe County, Florida. This unit includes Federal lands within NKDR (912 ac (369 ha)), State lands (228 ac (92 ha)), County lands (144 ac (58 ha)), and property in private or other ownership (96 ac (39 ha)). State lands are interspersed within NKDR lands and managed as part of the Refuge.

This unit was occupied at the time the species was listed and is currently occupied by one Big Pine Partridge pea population. This unit contains all the physical or biological features, including suitable climate, hydrology, substrate, associated native plant species, and disturbance regimes, essential to the conservation of the species.

Special management considerations or protection may be required within this unit to address lack of fire; nonnative plant and animal species; and sea level rise. Nonnative species control, prescribed fire, and mechanical vegetation treatments are all actions that help improve habitat that supports Big Pine partridge pea.

The unit is part of lands contained within the Lower Florida Keys National Wildlife Refuges (NWRs), which includes NKDR, Key West NWR, and Great White Heron NWR. The Comprehensive Conservation Plan (CCP) for the Lower Florida Keys NWRs promotes the enhancement of wildlife populations by maintaining and enhancing a diversity and abundance of habitats for native plants and animals and provides specifically for maintaining and expanding populations of plant species including Big Pine partridge pea. The Service conducts nonnative species control and prescribed fire in areas that could support Big Pine partridge pea.

Unit BPP1 is also designated critical habitat for the Florida leafwing (
Anaea troglodyta floridalis
) and Bartram's scrub-hairstreak (
Strymon acis bartrami
) butterflies.

Unit BPP2: Cudjoe Key, Monroe County, Florida

Unit BPP2 consists of 83 ac (33 ha) in Monroe County, Florida. This unit includes Federal lands within NKDR (66 ac (27 ha)), State lands (3 ac (1 ha)), County lands (1 ac (0.5 ha)), and property in private or other ownership (12 ac (5 ha)). State lands are interspersed within NKDR lands and managed as part of the Refuge.

This unit was occupied at the time the species was listed, but the population here may have since been extirpated (Possley 2020, pers. comm.). The unit does, however, still contain all the physical or biological features, including suitable climate, hydrology, substrate, associated native plant species, and disturbance regimes, essential to the conservation of the species.

Special management considerations or protection may be required within this unit to address lack of fire; nonnative plant and animal species; and sea level rise. Nonnative species control, prescribed fire, and mechanical vegetation treatments are all actions that help improve habitat that supports Big Pine partridge pea.

The unit is part of lands contained within the Lower Florida Keys NWRs, which includes NKDR, Key West NWR, and Great White Heron NWR. The CCP for the Lower Flo

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2022-21587. Public record. Not legal advice.