Endangered and Threatened Wildlife and Plants; Withdrawal of the Proposed Rule To Remove the Valley Elderberry Longhorn Beetle From the Federal List of Endangered and Threatened Wildlife
Federal RegisterSep 17, 2014
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R8-ES-2011-0063; FXES11130900000C2-123-FF09E32000]
RIN 1018-AV29
Endangered and Threatened Wildlife and Plants; Withdrawal of the Proposed Rule To Remove the Valley Elderberry Longhorn Beetle From the Federal List of Endangered and Threatened Wildlife
AGENCY:
Fish and Wildlife Service, Interior.
ACTION:
Proposed rule; withdrawal.
SUMMARY:
We, the U.S. Fish and Wildlife Service (Service), withdraw the proposed rule to remove the valley elderberry longhorn beetle (
Desmocerus californicus dimorphus
) from the Federal List of Endangered and Threatened Wildlife under the Endangered Species Act of 1973 (Act), as amended. This withdrawal is based on our determination that the proposed rule did not fully analyze the best available information. We find the best scientific and commercial data available indicate that the threats to the species and its habitat have not been reduced to the point where the species no longer meets the statutory definition of an endangered or threatened species.
DATES:
The Service is withdrawing the proposed rule published October 2, 2012 (77 FR 60238) as of September 17, 2014.
ADDRESSES:
The withdrawal of our proposed rule, comments and materials we received, and supplementary documents are available on the Internet at
http://www.regulations.gov
at Docket No. FWS-R8-ES-2011-0063. All comments, materials, and supporting documentation that we considered in this final agency action are available by appointment, during normal business hours, at: U.S. Fish and Wildlife Service, Sacramento Fish and Wildlife Office, 2800 Cottage Way, Suite W-2605, Sacramento, California 95825; telephone 916-414-6600; or facsimile 916-414-6713.
FOR FURTHER INFORMATION CONTACT:
Jennifer Norris, Field Supervisor, Sacramento Fish and Wildlife Office (see
ADDRESSES
section). Persons who use a telecommunications device for the deaf (TDD) may call the Federal Information Relay Service (FIRS) at 800-877-8339.
SUPPLEMENTARY INFORMATION:
Executive Summary
Why we need to publish this document.
Section 4 of the Act and its implementing regulations (50 CFR part 424) set forth the procedures for revising the Federal Lists of Endangered and Threatened Wildlife and Plants. Rulemaking is required to remove a species from the Federal Lists of Endangered and Threatened Wildlife and Plants, accordingly, we issued a proposed rule and 12-month petition finding on October 2, 2012 (77 FR 60238) to remove the valley elderberry longhorn beetle as a threatened species from the List of Endangered and Threatened Wildlife and to remove the designation of critical habitat for the subspecies. Based upon our review of public comments, comments from various Federal, county, and local agencies, peer review comments, comments from other interested parties, and new information that became available since the publication of the proposal, we reevaluated information in our files and our proposed rule. This document withdraws the proposed rule because the best scientific and commercial data available, including our reevaluation of information related to the species' range, population distribution, and population structure, indicate that threats to the species and its habitat have not been reduced such that removal of this species from the Federal List of Endangered and Threatened Wildlife is appropriate.
The basis for our action.
A species may warrant protection under the Act if it is found to be endangered or threatened throughout all or a significant portion of its range. A species may be determined to be an endangered species or threatened species because of one or more of the five factors described in section 4(a)(1) of the Act: (A) The present or threatened destruction, modification, or curtailment of its habitat or range; (B) overutilization for commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) the inadequacy of existing regulatory mechanisms; or (E) other natural or manmade factors affecting its continued existence. Based on our evaluation of the best scientific and commercial data available pertinent to threats currently facing the species and threats that could potentially affect it in the foreseeable future, we determine that threats have not been reduced such that the species no longer meets the statutory definition of an endangered or threatened species.
Peer review and public comment.
We sought peer review comments from independent specialists to ensure that our proposed delisting designation was based on scientifically sound data, assumptions, and analyses. We invited these peer reviewers to comment on our proposal to remove the valley elderberry longhorn beetle from the Federal List of Endangered and Threatened Wildlife. We also considered all other comments and information received during the public comment periods.
Acronyms and Abbreviations Used in This Document
We use many acronyms and abbreviations throughout this proposed rule. To assist the reader, we provide a list of these here for easy reference:
Act = Endangered Species Act of 1973
AFB = Air Force Base
BDCP = Bay Delta Conservation Plan
Cal-IPC = California Invasive Plant Council
CCP = Comprehensive Conservation Plan
CDFG = California Department of Fish and Game (see below)
CDFW = California Department of Fish and Wildlife (formerly CDFG)
CDPR = California Department of Pesticide Regulation
CDWR = California Department of Water Resources
CEQA = California Environmental Quality Act
CFG = California Fish and Game
CFR = Code of Federal Regulations
CNDDB = California Natural Diversity Database
Corps = Army Corps of Engineers
CNLM = Center for Natural Lands Management
CVFPP = Central Valley Flood Protection Plan
CVRMP = Central Valley Riparian Mapping Project
CWA = Clean Water Act
CWP = California Water Plan
DOD = Department of Defense
EO = Element Occurrence
ETL = (Army Corps of Engineers) Engineering Technical Letter
EPA = Environmental Protection Agency
EWPP = Emergency Watershed Protection Program
FR =
Federal Register
GCM = global climate model
GHG = greenhouse gas
GIC = Geographic Information Center
GIS = Geographic Information System
HCMP = Habitat Conservation Management Plan
HCP = Habitat Conservation Plan
HRMMP = Habitat Restoration, Monitoring, and Management Program
INRMP = Integrated Natural Resources Management Plan
IPCC = Intergovernmental Panel on Climate Change
LSA = Lake and Streambed Alteration
NAIP = National Agriculture Imagery Program
NEPA = National Environmental Policy Act
NCCP = Natural Community Conservation Planning
NRCS = Natural Resources Conservation Service
NWR = National Wildlife Refuge
PG&E = Pacific Gas and Electric Company
PGL = (Army Corps of Engineers) Policy Guidance Letter
PVA = Population Viability Analysis
SAMP = Special Area Management Plan
Service = U.S. Fish and Wildlife Service
SPFC = The (California) State Plan of Flood Control
USBR = U.S. Bureau of Reclamation
USDA = U.S. Department of Agriculture
USGS = U.S. Geological Survey
WRCC = Western Regional Climate Center
WRP = Wetland Reserve Program
WRRDA = Water Resources Reform and Development Act
Summary of Changes From the Proposed Rule
Based upon our review of public comments, comments from various Federal, county, and local agencies, peer review comments, comments from other interested parties, and new information that became available since the publication of the proposal (77 FR 60238; October 2, 2012), we reevaluated information in our files and our proposed rule, making changes as appropriate in this document. Where appropriate, we incorporated new information that became available since publishing the proposed rule, information received during the public comment periods, and in some cases provided additional discussion of information in our files that may not have been presented in adequate detail in the proposed rule. This document also provides important clarifications on the species' biology and threats to the species. Thus, this determination differs from the proposed rule as outlined below.
(1) Based on the results of the information received from peer reviewers and the public, we concluded that some species distribution information in the proposed rule was incorrectly presented. As a result, we reevaluated the quality of distribution information (occurrences) for the valley elderberry longhorn beetle that was included in our previous summaries (e.g., Valley Elderberry Longhorn Beetle Recovery Plan (Recovery Plan) (Service 1984, entire); proposed and final listing rules (43 FR 35636; August 10, 1978; 45 FR 52803; August 8, 1980); 5-year review (Service 2006a); and proposed delisting rule (77 FR 60238; October 2, 2012)). This required a reanalysis of the original data sets in our files throughout the range of the species.
(2) As a result of (1) above and our review of additional sources of information received during the open public comment periods, we reexamined existing information in our files. In this document, we provide either clarifications where necessary, additional or revised discussions where appropriate (e.g.,
Population Distribution
and
Current Distribution
sections under Background), or incorporate and discuss new information received (e.g., Climate Change and Pesticide discussion under
Factor E,
preliminary survey results using aggregation pheromones under
Population Structure
in Background).
(3) As a result of (1) and (2) above, as well as information received after the proposed rule published, we reevaluated and revised our description of the valley elderberry longhorn beetle's life history, and its population distribution, range, and occupancy. Our revised discussions are provided throughout the Background section.
(4) We revised the Summary of Factors Affecting the Species section, incorporating new or revised information, where appropriate, in our assessments for these factors. The substantial changes to the Background section required us to complete a detailed examination of the five-factor analysis information presented in the proposed rule for each threat to determine whether the discussions were still valid or required revisions. Thus, our threats analysis and associated summaries may differ, where appropriate, from that presented in the proposed rule.
The primary changes to this document as compared to the proposed rule are the result of our reanalysis of occurrence and distribution information of the valley elderberry longhorn beetle. Specifically, we restructured the five-factor analysis from our proposed rule to reflect our reanalysis of threats, including additional and more detailed information (e.g., invasive plants in
Factor A
and pesticides under
Factor E
). We provide a more extensive discussion of effects related to climate change in
Factor A,
and incorporate predictions from several regional climate models for the Central Valley region. We also incorporate detailed results of several studies (e.g., metapopulation analysis) and use this information to evaluate the current threats to the species. Finally, threats related to the effects of pruning (briefly mentioned in our proposed rule under a
Factor E
threat (Human Use) (77 FR 60263; October 2, 2012)) are discussed in this withdrawal under
Factor A.
(5) Based on our reanalysis and the changes described above under (1) through (4), and primarily as a result of the revised occurrence and distribution information that affects our evaluation of the factors impacting the species, we determined that the current and future threats are of sufficient imminence, intensity, or magnitude to indicate that the valley elderberry longhorn beetle is likely to become endangered within the foreseeable future throughout all of its range. Therefore, the valley elderberry longhorn beetle currently meets the definition of a threatened species, and we are withdrawing the proposed rule to delist the valley elderberry longhorn beetle.
Background
Previous Federal Actions
Please refer to the
Previous Federal Actions
section of the valley elderberry longhorn beetle proposed delisting rule (77 FR 60238, October 2, 2012) for a detailed description of the previous Federal actions concerning this species. On October 2, 2012, we proposed to remove the designation of the valley elderberry longhorn beetle as a threatened species under the Act (77 FR 60238). We opened a 60-day public comment period on the proposed rule that closed on December 3, 2012. On January 23, 2013 (78 FR 4812), we announced a 30-day reopening of the public comment period for our October 2, 2012, proposed delisting rule for the species.
Taxonomy and Species Description
The valley elderberry longhorn beetle,
Desmocerus californicus dimorphus,
is a member of the family Cerambycidae, subfamily Lepturinae, and genus
Desmocerus
(Chemsak 2005, pp. 6-7); adults are approximately 0.5 to 0.8 inches (in) (13 to 21 millimeters (mm)) long (Chemsak 2005, p. 6). In North America, the genus
Desmocerus
includes three species (
D. palliatus, D. californicus,
D. aureipennis
) and six subspecies (
D. c. californicus, D. c. dimorphus, D. a. aureipennis, D. a. cribripennis, D. a. piperi, D. a. lacustris
) in the United States and Canada (Chemsak 2005, pp. 4-12). Members of the genus
Desmocerus
are brightly colored and sexually dichromatic with antennal tubules that are not prominently produced at the apex (Chemsak 2005, pp. 2-3). The protonum (upper surface of the prothorax segment; the midsection (Evans and Hogue 2006, p. 293)) of the two
Desmocerus californicus
subspecies differ from the other two North American species (
D. palliatus, D. aureipennis
) with a disk that is densely, confluently punctate (with small depressions on the disk that flow or run together), but without large, irregular, and transverse rugae (ridges) that are about twice as long as broad (Chemsak 2005, p. 3).
Along the foothills of the eastern edge of the California coast range and in the southern San Joaquin Valley, the valley elderberry longhorn beetle range may overlap or abut portions of its range with the similar-looking California elderberry longhorn beetle (
Desmocerus californicus californicus
) (Talley
et al.
2006a, p. 5). Prior to 1972, the valley elderberry longhorn beetle was considered a separate and valid species (Halstead and Oldham 2000, p. 74). The two elderberry longhorn beetles are now considered two subspecies (Linsley and Chemsak 1972, pp. 7-8; Chemsak 2005, pp. 5-6). Valley elderberry longhorn beetle experts indicate that the small number of available specimens limits the ability to distinguish between the two types based on characteristics such as body length, elytra length and width, and antennal hair color (Talley
et al.
2006a, p. 5). Thus, the two subspecies can be identified with certainty only by the adult male coloration, such that valley elderberry longhorn beetle males have predominantly red elytra (wing cases) with four dark spots, while California elderberry longhorn beetle males have dark metallic green to black elytra with a red border; females of the two subspecies are similar in appearance (Talley
et al.
2006a, p. 4). Atypically colored (mostly dark) male elderberry longhorn beetles have been observed in both the center and eastern edge of the valley elderberry longhorn beetle's range (Talley
et al.
2006a, p. 5). Talley
et al.
(2006a, p. 7) recommend a systematic geographic morphological and genetic study to determine the degree of overlap and interbreeding between the two subspecies.
The obligate larval host plants for both elderberry longhorn beetles have been described as blue elderberry (
Sambucus mexicana
) and, to a lesser extent for the valley elderberry longhorn beetle, red elderberry (
Sambucus racemosa
) (Collinge
et al.
2001, p. 104; Holyoak 2010, p. 1). However, the current treatment of
Sambucus
in California (Family Adoxaceae) describes three taxa: Blue elderberry (
S. nigra
subsp.
caerulea
), black elderberry (
S. racemosa
var.
melanocarpa
), and red elderberry (
S. racemosa
var.
racemosa
) (Bell 2012, p. 160). As noted previously by others (e.g., Talley
et al.
2006a, p. 15), the taxonomic status of
Sambucus
is imprecise, and blue elderberry is currently described as “variable” and in need of further study (Bell 2012, p. 160). In this rule, we use the more general term, elderberry, to describe the host plant for the valley elderberry longhorn beetle since many of the elderberry surveys and their reported results do not distinguish, or do not identify, the two taxa known to be occupied by the valley elderberry longhorn beetle (i.e., blue elderberry and red elderberry). Local climate differences between the more coastal region occupied by the California elderberry longhorn beetle and the California Central Valley occupied by the valley elderberry longhorn beetle may promote different phenologies (e.g., flowering time) of the host plant and, therefore, differences in time of emergence for the two subspecies (Talley
et al.
2006a, p. 6).
Life History
Similar to other beetles, the valley elderberry longhorn beetle goes through several developmental stages. These include an egg, four larval stages (known as “instars,” with each instar separated by molting), pupa, and adult (Greenberg 2009, p. 2).
As reported by Arnold (1984, p. 4), females lay eggs singly on elderberry leaves and at the junction of leaf stalks and main stems, with all eggs laid on new growth at the outer tips of elderberry branches. Based on observations of
Desmocerus californicus
females along the Kings River, Halstead and Oldham (1990, p. 24) stated that females laid eggs at locations on the elderberry branch where the probing ovipositor (i.e., the female's egg-laying organ) could be inserted. In a laboratory setting, Barr (1991, p. 46) found that the majority of eggs laid by a female valley elderberry longhorn beetle were attached to leaves and stems of foliage (provided as food), with a preference for leaf petiole-stem junctions, leaf veins, and other areas containing crevices and depressions. Eggs are approximately 0.09 to 0.12 in (2.3 to 3.0 mm) long and reddish-brown in color with longitudinal ridges (Barr 1991, p. 4). Eggs are initially white to bright yellow (Talley
et al.
2006a, p. 8) and then darken to brownish white and reddish brown (Burke 1921, p. 451). Results of captive studies of
Desmocerus californicus
indicate the number of eggs produced per female vary, ranging from 8 to 110 (Burke 1921, p. 25; Arnold 1984, p. 4; Barr 1991, p. 51). Talley (2003, pp. 153-157) recorded a total of 136 larvae (and an additional 44 eggs that did not hatch) from one captive female valley elderberry longhorn beetle collected in 2002. Hatching success has been estimated at 50 to 67 percent of eggs laid, but survival rates of larvae are unknown (Talley
et al.
2006a, p. 7).
In a laboratory setting eggs hatched within a few days of oviposition (Talley 2003, p. 145), but in the natural setting, the time to eclosing (development from egg to first instar larvae) is unknown (Barr 1991, pp. 4-5). Based on laboratory observations, the first instar larvae may bore immediately into the green tissue of the elderberry stem at or near the egg site, or larvae may persist on the shrub surface for several hours (Halstead and Oldham 1990, p. 26). Previous studies of both subspecies of
Desmocerus californicus
(Burke 1921, p. 450; Linsley and Chemsak 1972, p. 4) estimated that the larval development rate inside the plant is 2 years, but laboratory observations have indicated that a 1-year cycle is possible (Halstead and Oldham 1990, p. 26). The boring of the larva creates a feeding gallery (set of tunnels) in the pith at the stem center (Burke 1921, p. 450; Barr 1991, pp. 4-5). While only one larva is found in each feeding gallery, multiple larvae can occur in one stem if the stem is large enough to accommodate multiple galleries (Talley
et al.
2006a, p. 8). Prior to pupation, the final (fifth) instar larva chews a larger pupal cavity in the pith of the stem and creates an exit burrow through the hardwood just below the surface of the bark of the plant, creating an exit hole (Halstead and Oldham 1990, p. 23), but then returns inside the plant stem, plugging the hole with wood shavings (also known as frass) (Talley
et al.
2006a, p. 8). These larvae move back down the feeding gallery to the enlarged pupal chamber packed with frass, where they metamorphose into pupae between January and April (Burke 1921, p. 452). Approximately 1 month later, they metamorphose into an adult, although the adult form may remain in the cavity for several weeks (Burke 1921, p. 452). The adults chew through the outer bark and emerge in the spring or early summer through the exit hole, generally coinciding with the flowering season of the elderberry (Burke 1921, p. 450; Halstead and Oldham 1990, p. 23).
Several studies or surveys have documented the presence of potential predators (e.g., earwigs, native and nonnative ants) of valley elderberry longhorn beetle larvae on elderberry shrubs or within stems (Barr 1991, p. 44; Huxel 2000, pp. 83-84; Holyoak and Graves 2010, pp. 16-17). The Argentine ant (
Linepithema humile
) is an invasive, nonnative species that has successfully colonized many areas of California (Vega and Rust 2001, p. 5), including permanent stream systems in parts of the Central Valley (Ward 1987, pp. 7-8; Huxel 2000, p. 84; Klasson
et al.
2005, pp. 7-8). Nectar and honeydew are important food sources for Argentine ants, but studies of feeding behavior have found that Argentine ants are opportunistic feeders that readily forage on protein sources such as insect larvae
or pupae, when available (Rust
et al.
2000, p. 209). For example, Way
et al.
(1992, pp. 428-431) found that Argentine ants easily located and removed exposed eggs laid by another arboreal insect borer (
Phoracantha semipunctata
(Coleoptera: Cerambycidae)) in studies conducted in eucalyptus stands in Portugal. See Summary of Factors Affecting the Species section below for additional discussion of predation threats to the valley elderberry longhorn beetle.
Collection records indicate that adult valley elderberry longhorn beetles can be observed from mid-March until early-June, though most records are from late-April to mid-May (Service 1984, p. 7). However, the adult stage is rare, both in space and time (Talley
et al.
2006b, p. 649); adults likely die within 3 months (Halstead and Oldham 1990, p. 22). In a laboratory setting, Arnold (1984, p. 4) recorded females living up to 3 weeks, but males lived no more than 4 or 5 days. Similarly, Barr (1991, p. 46) described a life span of 17 days for a captive male and 25 days for two captive females. Halstead and Oldham (1990, p. 25) recorded caged adults living from 4 to 66 days in their experimental studies.
The exit holes created in elderberry stems by the emerging adult eventually heal, but distinct scars remain on the plant stem (Talley
et al.
2006a, p. 9). Although the presence of exit holes is used to survey and estimate population size for the valley elderberry longhorn beetle (Talley
et al.
2006a, p. 10) (see additional discussion in
Population Distribution
section), this survey technique can be problematic as an estimate of occupancy for several reasons. First, the exit holes of both the valley elderberry longhorn beetle and the California elderberry longhorn beetle are reported to be identical and both beetles use the same elderberry taxa as their host plants (Arnold 2014b, pers. comm.), making it difficult to determine occupancy of the two subspecies in areas where their ranges may overlap. Second, surveys may have included observations of exit holes in dead stems, rather than only those found in live elderberry stems even though the species uses only live host plants. Third, once an elderberry stem is abandoned by the valley elderberry longhorn beetle, other species can occupy the holes and fill them with frass, making it difficult to confirm that the feeding chamber was created by the valley elderberry longhorn beetle (Talley
et al.
2006a, p. 10). Finally, birds may also enlarge or rework valley elderberry longhorn beetle exit holes making them difficult to identify as such (Jones and Stokes Associates 1987, p. 38).
Adult Behavior and Ecology
Because of the species' rarity, its short-lived adult form, and difficulty in observing adults in the field, few studies document the behavior of adult valley elderberry longhorn beetles. Where observed, adults have been described as feeding on the nectar, flowers, and leaves of the elderberry plant (Arnold 1984, p. 4; Collinge
et al.
2001, p. 105), or flying between trees (Service 1984, p. 7). Mating likely begins fairly quickly upon emergence. In field studies conducted in the north Sacramento area, Arnold (1984, p. 4) noted that male adult valley elderberry longhorn beetles appear more active than female adults, and males were observed taking short flights both within elderberry shrubs or to another shrub.
Dispersal distances for the valley elderberry longhorn beetle are unknown. Based on site occupancy and patterns of colonization and extinction from 1991 to 1997, Collinge
et al.
(2001, p. 111) concluded that the valley elderberry longhorn beetle has limited dispersal ability. In this and following sections (i.e.,
Adult Behavior and Ecolo
gy,
Population Structure,
and
Summary
under Background), the term “extinction” refers to the observations defined and described in the original citations (e.g., Collinge
et al.
2001, entire, and Zisook 2007, entire), and does not refer to extinction of the valley elderberry longhorn beetle. Talley
et al.
(2007, p. 28) concluded the abundance of exit holes was spatially clustered over distances of 33 to 164 feet (ft) (10 to 50 meters (m)) in alluvial plain, riparian corridors, and upper riparian terrace habitats along portions of the American River Basin. In this same study, the average distance between the nearest neighboring (recent) exit hole was estimated at 141 ft (43 m); however, there was a wide range in the distances measured (plus or minus 144 ft (44 m)) (Talley
et al.
2007, p. 28), making it difficult to draw definitive conclusions for this spatial relationship. Based on these data, Talley
et al.
(2007, p. 28) estimated the dispersal distance of an adult valley elderberry longhorn beetle from its emergent site to be 164 ft (50 m) or less (Talley
et al.
2007, p. 28). However, Arnold (2014a, pers. comm.) has observed males flying at least 1 mile (mi) (1.6 kilometers (km)) in areas of good habitat. Given the varying results of these studies (i.e., Collinge
et al.
2001; Talley
et al.
2007; Arnold 2014a, pers. comm.) and lack of comprehensive studies of adult behaviors (e.g., mark and recapture studies), we are not able to accurately define a precise dispersal distance or assess how dispersal or other behaviors affect population persistence for this species. However, we believe that the dispersal ability for this species range is fairly limited.
Habitat
The valley elderberry longhorn beetle occupies portions of the Central Valley of California (also known as the Great Valley of California). The Central Valley is bounded by the Cascade Range to the north, the Sierra Nevada to the east, the Tehachapi Mountains to the south, and the coastal ranges and San Francisco Bay to the west. The valley is a large agricultural region drained by the Sacramento and San Joaquin Rivers and represents one of the more notable structural depressions in the world with much of the valley close to sea level in elevation with very low land surface relief, though elevations are higher along the valley margins (U.S. Geological Survey (USGS) 2013a). The climate in the Sacramento Valley and the San Joaquin Basin, which comprise the northern two-thirds of the Central Valley, can be characterized by cool, rainy winters and hot, dry summers (USGS 2013a). The average annual rainfall for the Central Valley ranges from 5 inches (12.7 centimeters (cm)) at the southern end to over 30 inches (76.2 cm) at the northern end (U.S. Bureau of Reclamation (USBR) 2014). With more than three-quarters of this rain coming during a 5-month period (December through April), seasonal floods are common in the valley due to heavy winter and spring runoffs. This precipitation pattern often creates water shortages in the summer and fall when rain is most needed for irrigation purposes; in low rainfall years, drought conditions are often observed in the valley (USBR 2014).
In addition to rain falling within the valley itself, snowpack in the Sierra Nevada Mountains to the east historically provided flows from numerous rivers and streams into both the Sacramento Valley and the San Joaquin Valley through late spring (Katibah 1984, p. 24). These river systems have been altered by artificial levees, river channelization, dam construction, and water diversions (Katibah 1984, p. 28).
The primary host plant of the valley elderberry longhorn beetle, blue elderberry, is an important component of riparian ecosystems in California (Vaghti
et al.
2009, p. 28). As part of the remnant riparian forests in the Central Valley, elderberry provides wintering, foraging, and nesting habitat for birds (Gaines 1974, entire; Gaines 1980,
entire) and supporting habitat for other boring insects and spiders (Barr 1991, p. 44). Its berries, leaves, and flowers provide food for wildlife, particularly during dry summer months (Vaghti
et al.
2009, pp. 28-29). Elderberry seeds are likely dispersed by vertebrates, particularly birds (Talley 2005, p. 57). Elderberry seedlings have shallow roots, and high rates of mortality have been observed in the field (Talley 2005, p. 57). Lower seedling mortality rates (about 25 percent in the first year of planting) have been reported from areas where elderberry plants have been transplanted or where new elderberry seedlings have been planted (i.e., mitigation sites) where site conditions are managed (Holyoak
et al.
2010, p. 48).
A 1991 survey for the valley elderberry longhorn beetle between the Central Valley and adjacent foothills recorded elderberry plants (i.e., both red and blue elderberry) in habitats ranging from lowland riparian forest to foothill oak woodland, with elevation ranges from 60 to 2,260 ft (18.3 to 689 m) (Barr 1991, p. 37). Historically, the riparian forests in the Central Valley consisted of several canopy layers with a dense undergrowth and included Fremont cottonwood (
Populus fremontii
), California sycamore (
Platanus racemosa
), willows (
Salix
sp.), valley oak (
Quercus lobata
), box elder (
Acer negundo
var.
californicum
), Oregon ash (
Fraxinus latifolia
), and several species of vines (e.g., California grape (
Vitis californica
) and poison oak (
Toxicodendron diversilobum
)) (Service 1984, p. 6). These plant communities encompass several remaining natural and semi-natural floristic vegetation alliances and associations within the Great Valley Ecoregion of California (see Buck-Diaz
et al.
2012, pp. 12-23). The 1991 survey conducted by Barr noted that elderberry was found most frequently in mixed plant communities, and in several types of habitat, including non-riparian locations, as both an understory and overstory plant (Barr 1991, pp. 40-41) with adults and exit holes created by the valley elderberry longhorn beetle found most commonly in riparian woodlands and savannas (Barr 1991, p. 41). Based on surveys completed along the Sacramento River, Gilbart (2009, p. 51) concluded that the valley elderberry longhorn beetle shows a preference for moderate amounts of cover, but that its occupancy is reduced with some canopy-producing plants, such as box elders, cottonwoods, and willows.
Nonnative plants observed in vegetation communities containing elderberry include giant reed (
Arundo donax
), brome (
Bromus
spp.), and bur chervil (
Anthriscus caucalis
) (Vaghti
et al.
2009, pp. 33-35). Black locust (
Robinia pseudoacacia
) and black walnut (
Juglans hindsii
) have been identified as important invasive species that can displace native plants in riparian floodplains in the Central Valley (Hunter 2000, p. 275; Vaghti
et al.
2009, pp. 33-35) (see Summary of Factors Affecting the Species section below).
Talley
et al.
(2006a, p. 10) stated that the valley elderberry longhorn beetle is found most frequently and most abundantly in areas that support significant riparian zones (see also Talley
et al.
2007, discussed below). In a study to evaluate the occupancy of the valley elderberry longhorn beetle (based on exit hole observations) in roadside habitats in the northern Central Valley (2006-2008), Talley and Holyoak (2009, p. 8) found that site occupancy rates and rates of elderberry shrub occupancy within occupied sites were higher in riparian vegetation compared with non-riparian vegetation. Hydrological processes, specifically inundation duration and frequency, when measured by relative elevation above a river or creek floodplain, were found to significantly influence the distribution of elderberry in the lower alluvial reaches of the American River, Cache Creek, Cosumnes River, and Putah Creek (Talley 2005, pp. 52, 55, 66). The highest frequency of elderberry shrubs was found within an intermediate relative elevation gradient, that is, between areas influenced by flooding processes (low elevations) and water availability (higher elevations) (Talley 2005, pp. 45, 66). Talley (2005, pp. 56-58) also noted that the differences in relationships between elderberry abundance (number of shrubs within each elderberry patch), lateral size (shrub diameter), and stress level (proportion of dead stems per shrub) within the four river systems studied were attributed to stochastic (random) processes related to seed dispersal patterns and seedling mortality.
Several studies have evaluated specific elderberry plant characteristics (e.g., size of stems, density of stems, and height above ground) relative to the valley elderberry longhorn beetle's life-history requirements and its abundance or presence (Jones and Stokes Associates 1987, pp. 27-32; Barr 1991, pp. 37-42; Collinge
et al.
2001, pp. 107-109; Talley 2005, pp. 14-15, 17-19; Talley
et al.
2007, entire; Holyoak and Koch-Munz 2008, entire). A detailed analysis of habitat and habitat quality for the valley elderberry longhorn beetle was completed based on surveys from 2002 to 2004 within one section of the American River Basin (American River Parkway) (Talley
et al.
2007, entire). The study identified several predictors of habitat occupancy in the area surveyed and found that, in general, density of elderberry shrubs and shrub size, number of stems, and range of branch sizes were the most influential predictor variables (Talley
et al.
2007, p. 30). Valley elderberry longhorn beetle exit holes were observed most frequently in elderberry stems or branches with a diameter of 0.8 to 2.76 inch (2 to 7 cm) and at a height of 0 to 3.28 ft (0 to 1 m) above ground, which may be the result of the size of the main stems of elderberry shrubs (Talley
et al.
2007, p. 30). Of the four types of habitats evaluated within the study area, riparian cover types contained the greater quality of habitat, specifically upper riparian terrace and lower alluvial plain habitats (Talley
et al.
2007, p. 30).
There are limited studies on the relationship of the valley elderberry longhorn beetle's life-history features and those of its host plants, and the significance of this relationship to the ecology of riparian or other native plant communities where the species is found. Based on comprehensive surveys of elderberry taxa surveyed within the Central Valley in 1991, Barr (1991, p. 50) concluded that the presence of the valley elderberry longhorn beetle was not a factor in the health of elderberry host plants, nor were unhealthy host plants a factor determining the presence of the beetle. Gilbart (2009, entire) evaluated the relationship between the occupancy of the valley elderberry longhorn beetle and the health of blue elderberry planted at restoration sites along the Sacramento River (within the Sacramento River National Wildlife Refuge (NWR)). Results from this study found a correlation between occupancy and dead biomass (versus between occupancy and age), which supports results from other studies regarding the valley elderberry longhorn beetle's preference for plants with partial bark damage or that are otherwise stressed (e.g., low to moderate levels of damaged stems from pruning or burning), or for shrubs with, on average, 25 to 50 percent dead stems (Arnold 1984, p. 4; Holyoak and Koch-Munz 2008, pp. 447-448).
Gilbart (2009, p. 54) stated that valley elderberry longhorn beetles likely use olfaction to locate host plants and mates, and volatiles released from the stressed tissue in elderberry shrubs are likely to be the initial cue used for host plant and mate location. This analysis also found that, although the exit holes
created by the valley elderberry longhorn beetle may increase the dead biomass of elderberry shrubs, an increase in plant cover has a greater effect on dead biomass and is independent of the occupancy of the beetle (Gilbart 2009, pp. 53-54). Additional studies are needed to determine the relationships between the valley elderberry longhorn beetle's occupancy and: (1) The regenerative ability and timing of elderberry stem growth; (2) the beetle's observed preference for elderberry stems of a certain minimum diameter relative to the host plants' life history; and (3) other factors related to the ecological role of elderberry found in the species' range in the Central Valley.
In an unpublished evaluation of environmental factors important to the valley elderberry longhorn beetle, Zisook (2007, entire) evaluated colonization and extinction events based on survey data from the Talley
et al.
(2007, entire) study along the American River Parkway. Zisook (2007, p. 5) found that colonization events were more likely to occur on shrubs located on north-facing slopes and on relatively large and previously occupied shrubs. Extinction events were more likely to be associated with relatively small elderberry shrubs, shrubs with stem damage, and in areas with larger floodplain widths (Zisook 2007, p. 5). In their evaluation of elderberry characteristics at mitigation sites compared with natural sites, Holyoak and Koch-Munz (2008, pp. 449-450) noted that, within mitigation sites, the abundance of the valley elderberry longhorn beetle
per elderberry shrub
was positively related to the size and age of the mitigation site, and the species was more likely to be present in elderberry shrubs with low levels of damage (e.g., partial bark damage) at these sites (see also discussion in
Adult Behavior and Ecology
section above). Relatedly, Talley
et al.
(2007, p. 28) found that the presence of recent exit holes was correlated with previous occupancy (that is, 73 percent of elderberry shrubs with recent holes also had old holes). A similar result was found in a 2010 survey effort, in which all but one watershed sampled had both new holes and old holes (in both dead and live wood) (Holyoak and Graves 2010, p. 12). Additional habitat characteristics relative to spatial relationships of elderberry shrubs and occupancy of the valley elderberry longhorn beetle are summarized in our metapopulation structure discussion (see
Population Distribution
section below).
Population Distribution
There are few recorded observations of adult valley elderberry longhorn beetles; many of the locations for this species in various references, including previous Service documents, are based exclusively on observations of exit holes. The population distribution of the valley elderberry longhorn beetle described in our proposed delisting rule (77 FR 60238; October 2, 2012) relied heavily on the records provided in the California Natural Diversity Database (CNDDB) as Element Occurrences (EOs). The CNDDB, maintained by the California Department of Fish and Wildlife (CDFW; formerly known as California Department of Fish and Game (CDFG)), is an ongoing effort to include observations and survey reports for separate EOs of all of the species and subspecies tracked by the database. However, because contribution to the database is not mandatory, some observations or surveys as well as negative survey results for plants and animals (including the valley elderberry longhorn beetle) are not included in the database; therefore, the CNDDB should not be considered an exhaustive or comprehensive inventory of all rare species in California (CDFW 2014c). For animals with limited mobility, which includes most invertebrates, an EO is defined as a location where a specimen was collected or observed, and is assumed to represent a sample of a breeding population (CDFG 2007, p. 1). Sequential surveys are accumulated in EO reports for each location of a species.
There are important limitations to consider when using the CNDDB records to examine the population distribution and abundance of the valley elderberry longhorn beetle. First, despite the date (year) of the observations, CNDDB considers all occurrences of the valley elderberry longhorn beetle as presumed extant, even though many of these records are more than 20 years old. Second, the occurrence rank (a measure of the condition and viability of a particular occurrence that takes into account population size, viability, habitat quality, and disturbance) used by CNDDB (based on NatureServe definitions; NatureServe 2014) for many of the valley elderberry longhorn beetle EOs are considered “poor” (occurrence has a high risk of extirpation) or “unknown” (rank not assigned due to lack of sufficient information on the occurrence). In addition, many of the records described in the CNDDB report represent only observations of exit holes. As noted above in
Life History
section, these observations may represent: (1) Old exit holes created by the valley elderberry longhorn beetle; (2) exit holes created by the California elderberry longhorn beetle within areas where their ranges overlap; or (3) holes created by other species.
Our review of the 2013 CNDDB EO report for the valley elderberry longhorn beetle found that 72 percent (142 of 196) of the EOs represent observations of only exit holes, and 23 percent (46 of 201) of the EOs are described as adult beetles (male, female, or unknown sex) (CNDDB 2013, entire; Arnold 2014a, pers. comm.). Only 12 percent (24 of 201) of the EOs identify observations of adult males (CNDDB 2013, entire; Arnold 2014a, pers. comm.), and four of these records (within Tulare County) are likely to be observations of the California elderberry longhorn beetle since no typically colored male specimens have been observed or collected from this County (Talley
et al.
2006a, p. 5).
Presumed Historical Range
Prompted by comments received from peer reviewers, local agencies, the public, and other interested parties during our two open comment periods on the proposed delisting rule (77 FR 60238; October 2, 2012: 78 FR 4812; January 23, 2013), and our reassessment of the CNDDB occurrences (CNDDB 2013, entire), and other references (e.g., elderberry mitigation or conservation banks, biological opinions prepared by the Service, and other unpublished reports), we are defining in this withdrawal notice the presumed historical range of the valley elderberry longhorn beetle based on:
(1) A georeferenced version (Service 2014, Geographic Information System (GIS) analysis) of the distribution map illustrated in Chemsak (2005, p. 7).
(2) The distribution defined in Talley
et al.
(2006a, pp. 4-6), which was based on museum specimens and sightings of adult males.
(3) The distribution map (also georeferenced) of museum and other specimens depicted in Halstead and Oldham (1990, p. 51 (Figure 22)).
(4) Locations of observations of adult male valley elderberry longhorn beetles described in the CNDDB report (CNDDDB 2013, entire) or in other survey results not recorded in CNDDB (River Partners 2010, entire; Arnold and Woollett 2004, p. 8; Arnold 2014a, pers. comm.).
We did not use the locations presented in Halstead and Oldham (2000, p. 75) to develop this presumed historical range since their publication did not distinguish between the two subspecies.
The presumed historical range of the valley elderberry longhorn beetle represents a patchy distribution from Tehama County to Fresno County, as shown in Figure 1 below (Service 2014, GIS analysis). Observations of adult beetles have been reported from Shasta County in 2008 and 2009 (CNDDB EO 218), as well as exit holes in 1991 and 2007 through 2012 (CNDDB EO 218; Holyoak and Graves 2010, p. 23), and an unconfirmed adult male valley elderberry longhorn beetle in 2013 (Souza 2014, pers. comm.). We did not include Shasta County within our presumed historical range because of the difficulty in distinguishing female valley elderberry longhorn beetle from female California elderberry longhorn beetle, the unconfirmed observation of an adult male valley elderberry longhorn beetle, and the absence of museum specimens from this area. However, we acknowledge that the recent observations of exit holes in portions of Shasta County (along the Sacramento River) may represent an expansion of the historic range of the valley elderberry longhorn beetle to this location. With regard to recorded CNDDB observations of valley elderberry longhorn beetle in Tulare County, it is important to note that there is significant uncertainty as to whether the male and female adult beetles observed in that area represent observations of the valley elderberry longhorn beetle or the California elderberry longhorn beetle (CNDDB EOs 63, 66, 128, 154). Based on the distribution map prepared by Chemsak (2005, pp. 6-7) and the discussion (and map) presented in Talley
et al.
(2006a, pp. 5-6), it is reasonable to conclude that the Tulare County observations likely represent the California elderberry longhorn beetle.
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Current Distribution (Since 1997)
The most recent, comprehensive rangewide survey by observers known to be qualified to detect occupancy of the valley elderberry longhorn beetle was conducted in 1997 (see Collinge
et al.
2001, entire). Collinge
et al.
(2001, entire) resampled 65 of 79 sites surveyed by Barr in 1991 and 7 additional sites within the Central Valley in 1997.
Within the last 10 years, surveys in the Central Valley for the valley
elderberry longhorn beetle have included the following:
(1) Examining 4,536 elderberry shrubs in the Lower American River (14.9 mi) (24 km) and Putah Creek (28 km (17.4 mi)) (Talley 2005, entire).
(2) Conducting exit hole surveys in 2010 of both elderberry shrubs (441) and stems (4,247) in 10 watersheds from Shasta to Tulare Counties (34 sites) (Holyoak and Graves 2010, entire).
(3) Conducting surveys of potential and occupied valley elderberry longhorn beetle habitat within riparian areas along the Stanislaus River (59 mi (95 km)) and San Joaquin River (12 mi (19.3 km)) in 2006 (River Partners 2007, entire).
It should be noted that some of the surveys described above were conducted within areas located adjacent to public roads or within accessible areas such as public parks (i.e., “convenience” sampling) in order to more easily access and examine shrubs for exit holes, or to better observe adults. Therefore, survey results should not be considered as a complete representation of the entire population distribution (or occupancy) of the valley elderberry longhorn beetle at the time of the particular survey.
In this withdrawal, we provide a reevaluation of the valley elderberry longhorn beetle occurrence records described in our proposed rule, and we also incorporate new information received since the proposed delisting rule was published on October 2, 2012 (77 FR 60238). This reanalysis now provides the most accurate assessment of the presumed extant occurrences of the valley elderberry longhorn beetle (based on the best available commercial and scientific information) as compared to what was presented in the proposed rule. Specifically, we started with identifying CNDDB EOs (adults or exit holes, any age) observed since 1997 (past 16 years), as this was the year in which the most recent, comprehensive rangewide survey by observers known to be qualified to detect occupancy of the species was conducted (Collinge
et al.
2001). Next, a subset of these CNDDB EO records were used if they had an Occurrence Rank of “fair” (occurrence characteristics are non-optimal, and occurrence persistence is uncertain in current conditions), “good” (occurrence has favorable characteristics and is likely to persist for the foreseeable future (20-30 years), if current conditions prevail) or “excellent” (occurrence has optimal or exceptionally favorable characteristics and is very likely to persist in foreseeable future (20-30 years), if current conditions prevail) (NatureServe 2014).
In addition, we incorporated into our reanalysis records from:
(1) Observations of exit holes (recent holes only based on level of detail available) from surveys conducted in 1997 (Collinge
et al.
2001, entire; Collinge 2014 pers. comm.).
(2) Exit hole (any age) and adult beetle locations in four watersheds (Lower American River, Putah Creek, Cache Creek, Cosumnes River) from 2002-2005 surveys (Talley 2014a, pers. comm.).
(3) Exit hole (any age) locations from 10 watersheds as described in Holyoak and Graves (2010, entire).
(4) Exit hole (any age) locations along the Stanislaus and San Joaquin Rivers from River Partners (2007, entire).
(5) Adult beetle observations along the Feather and Sacramento Rivers from River Partners (2010 and 2011; entire).
(6) Exit hole (any age based on detailed information available from recent data sets) locations recorded at Beale Air Force Base (Department of Defense (DOD 2014, unpublished GIS data)).
Of the currently described 201 CNNDB records (CNDDB 2013, entire) for the valley elderberry longhorn beetle, 142 EOs represent observations of only exit holes, 52 EOs represent observations from 1997 to 2013, and 25 EOs represent observations from 1997 to 2013 with an Occurrence Rank of “fair,” “good,” or “excellent.”
We then selected the locations of observations (exit holes or adults) found within our defined presumed historical range (as shown in Figure 1) for the valley elderberry longhorn beetle. These locations (which represent 17 EOs) are summarized in Table 1 by their geographical location (e.g., hydrological feature) and illustrated in Figure 2. Of note, we could not locate (using GIS software (Service 2014, GIS analysis) with an acceptable level of accuracy the six mitigation site survey locations (2005 and 2006) from Holyoak and Koch-Munz (2008, Appendix A1); thus, these six locations were not included in Table 1 or Figure 2. However, many, if not all, of these six mitigation site locations are within watersheds where occupancy (exit holes) of the valley elderberry longhorn beetle has been observed within the last 16 years, or are locations that were reported in the CNDDB EO report (CNDDB 2013, entire).
Table 1—Geographical Locations of Valley Elderberry Longhorn Beetle Occurrences Since 1997 in California, Grouped by Hydrologic Unit. Based on Observations (Adults or Exit Holes), Including CNDDB EOS With an Occurrence Rank of “Fair, Good, or Excellent,” and Other Survey Results Within the Valley Elderberry Longhorn Beetle's Presumed Historical Range
[See Figure 1]
[Sources: Collinge
et al.
2001; Holyoak and Graves 2010; River Partners 2007, 2010, 2011; CNDDB 2013; Collinge 2014, pers. comm.; Talley 2014a, pers. comm.; DOD 2014.]
Hydrologic unit
Geographical location
Type of observation
(adult,
1
exit holes)
Year last
observed
Thomes Creek-Sacramento River:
Millrace Creek
Adult (unknown), Exit Holes
2001
Salt Creek
Adult (both), Exit Holes
2001
Sacramento River (SSE of Red Bluff)
Adult (both), Exit Holes
2001
Big Chico Creek-Sacramento River:
Sacramento River (E of Corning)
Exit Holes
2010
Sacramento River (Glenn-Colusa Irrigation District Mitigation Site)
Adult (male)
2002
Sacramento River Mitigation Area (aggregation of shrubs, many exit holes
2
)
Exit Holes
2003
Big Chico Creek (two locations)
Exit Holes
1997
Sacramento-Stone Corral:
Sacramento River (N of Colusa)
Exit Holes
2010
Honcut Headwaters-Lower Feather:
Feather River (SW of Oroville) (three locations)
Exit Holes
2010
Feather River (Feather River Elderberry Transplant Area)
Adult (both)
2010
Feather River (5 mi N of Marysville)
Exit Holes
1997
Feather River (Star Bend Elderberry Mitigation Site) (two locations)
Adult (both)
2010
Feather River (10 mi SW of Wheatland) (two locations)
Exit Holes
2010
Reeds Creek (Beale AFB)
Exit Holes
2012
Upper Bear:
Bear River (SSE of Wheatland)
Adult (unknown), Exit Holes
2003
Bear River (4 mi SW of Wheatland) (three locations)
Exit Holes
2010
Best Slough/Dry Creek (Beale AFB)
Exit Holes
2005
North Fork American:
Folsom Lake (NW Shore)
Exit Holes
1997
Folsom Lake
Exit Holes
2010
Lower American:
Miners Ravine (tributary of Dry Creek)
Exit Holes
1997
American River Parkway (aggregation of shrubs, many exit holes)
Adult (female), Exit Holes
2010
Upper Cache:
Cache Creek (many locations)
Exit Holes
2003
Lower Sacramento:
Willow Slough (SW of Esparto)
Adult (male), Exit Holes
2001
RD-900 Canal (W of Sacramento River)
Adult (both)
2006
Sacramento River (SW of Sacramento)
Adult (male)
2005
Upper Putah:
Putah Creek (aggregation of shrubs, many exit holes)
Adult (unknown), Exit Holes
2010
Upper Cosumnes:
Cosumnes River (24 locations)
Exit Holes
2003
Upper Mokelumne:
South of Mokelumne River
Exit Holes
2006
Upper Calaveras:
Calaveras River
Exit Holes
2000
Upper Stanislaus:
Stanislaus River (N of Modesto) (two locations, several areas)
Exit Holes
2010
Bear Creek (tributary of Stanislaus River)
Adult (female)
2002
South of Mountain Pass Creek (S of Yosemite Jct.; tributary of Stanislaus River)
Adult (female)
2007
Upper Tuolumne:
Tuolumne River
Exit Holes
1999
Algerine Creek (tributary of Tuolumne River)
Exit Holes
2007
Upper Merced:
Merced River (S of Modesto)
Exit Holes
2010
Tulare Lake Bed:
Kings River (E of Centerville)
Adult (both), Exit Holes
1998
1
Some adult valley elderberry longhorn beetle observations were not identified as either male or female, and some observations were identified to include both males and females.
2
The term “many” in this table is defined as a value greater than 50.
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Table 1 represents a reevaluation of the 26 “locations” listed in the proposed rule (77 FR 60242-60243 (Table 1); October 2, 2012) based on our assessment of observations since 1997, while incorporating our current description of the presumed historical range of the valley elderberry longhorn beetle (see
Presumed Historical Range
section above). This revision of presumed extant occurrences (as
compared to Table 1 in the proposed delisting rule) is based on: (1) A review of the quality of the CNDDB EOs (type of observation, the year of last observation, and occurrence rank); (2) additional data sets (as discussed above and represented in Figure 2); (3) comments received from the peer reviewers, Federal, County, and local agencies, the public, and other interested parties relative to occupancy; and (4) a new grouping of geographical locations based on hydrologic units defined by a national watershed boundary dataset (USGS 2013b). Since some observations did not distinguish between old and recent exit holes, we include observations of both old (greater than 1 year old) and recent (i.e., greater than or equal to 1 year) exit holes for most survey results.
Taken together, these data (presented in Table 1 and Figure 2) describe an uncommon or rare, but locally clustered, occupancy of the valley elderberry longhorn beetle within the presumed historical range over the past 16 years within approximately 18 hydrologic units (USGS 2013b) and 36 geographical locations within the Central Valley. The 36 geographical locations are considered to be discrete from each other based on a presumed maximum dispersal distance of approximately 1 mi (1.6 km) based on observations of male beetles from Arnold (2014a, pers. comm.), but in some areas (e.g., Putah Creek) they include several areas of elderberry habitat within that location. As shown in Table 1, 61 percent (22 of 36) of the geographical locations are areas where only exit holes have been used to define occupancy, which is the result of both the survey methods used and the difficulty in observing adult valley elderberry longhorn beetles. Twenty-five percent (9 of 36) of the geographical locations within 4 hydrologic units represent observations of adult males recorded since 1997.
Restoration and Mitigation Sites
A large amount of monetary resources has been invested in floodplain restoration along sections of the Sacramento River for the purpose of restoring riparian areas that serve as habitats for native plants and wildlife, including the valley elderberry longhorn beetle (Golet
et al.
2008, p. 2; Golet
et al.
2013, entire). Holyoak
et al.
(2010, p. 50) estimated that an average of 2.5 mitigation sites were initiated per year, with more than 1,000 elderberry and 6,000 native plants planted per year for the 1989-1999 time period. Our proposed rule described a number of conservation easements or banks, mitigation and restoration sites, and other conserved areas that have been established within the current range of the valley elderberry longhorn beetle, which we estimated to be approximately 21,536 ac (8,715 ha) (77 FR 60256-60258; October 2, 2012).
Mitigation for the valley elderberry longhorn beetle generally consists of planting elderberry seedlings and associated native plants and transplanting mature elderberry shrubs from impacted sites to mitigation sites (Holyoak
et al.
2010, pp. 44, 46). In our proposed rule, we provided an estimate (642 to 1,900 ac (260 to 769 ha)) of valley elderberry longhorn beetle habitat protected through measures associated with section 7 consultations or through conservation or mitigation measures established through Habitat Conservation Plans permitted under section 10 of the Act (see
Factor D
discussion below) (77 FR 60258; October 2, 2012). We also identified another large riparian area (4,600 ac (1,862 ha)) along the American River (the American River Parkway) that contains critical habitat for the valley elderberry longhorn beetle, but the amount of occupied elderberry habitat is not known (77 FR 60258; October 2, 2012). However, we indicated in the proposed rule that an unknown proportion within these areas (i.e., conservation easements, mitigation sites, restoration sites, etc.) actually contain elderberry shrubs and only a proportion of that (unknown) estimate contains habitat occupied by the valley elderberry longhorn beetle.
By mid-2013, approximately 2,698 elderberry shrubs (covering 1,000 ac (405 ha)) were expected to be planted by Pacific Gas and Electric Company (PG&E) in conservation areas located near or adjacent to existing elderberry populations in the Central Valley (Ross-Leech 2012, pers. comm.). Valley elderberry longhorn beetle exit holes have been recorded at five locations where PG&E is conducting biannual monitoring (Ross-Leech 2012, pers. comm.). PG&E has established mitigation sites in several counties to compensate for project-specific effects to the valley elderberry longhorn beetle. Fifteen sites are located in Tehama and Yolo Counties, with approximately 1,228 elderberries successfully established (as of 2002), and occupancy of the valley elderberry longhorn beetle (adults or exit holes) has been observed at 11 of the 15 sites (Ross-Leech 2012, pers. comm.).
The Center for Natural Lands Management (CNLM) manages four preserves in the Central Valley where naturally occurring or planted elderberry are found; CNLM owns three and holds a conservation easement on the other (Rogers 2012, pers. comm.). Management practices being implemented at these sites appear to be consistent with maintaining elderberry habitat; however, the protection and stabilization of the valley elderberry longhorn beetle is not the primary management objective for the preserves, and funding is limited for management activities to specifically support valley elderberry longhorn beetle conservation (Rogers 2012, pers. comm.) Two of these preserves (Pace and Keeney in San Joaquin and Butte Counties, respectively) have recorded valley elderberry longhorn beetle exit holes within the past 3 to 10 years; however, no monitoring for the species has been conducted within the other two preserves (Oxbow in San Joaquin County and Dublin Ranch in Alameda County) or within the Mehrton conservation bank (Sacramento County) that CNLM neither owns nor manages (Rogers 2012, pers. comm.). We describe restoration efforts of elderberry habitat located within National Wildlife Refuges in the Central Valley below, under
Factor D,
Other Conservation Programs.
Transplanted elderberry shrubs appear to be important in the colonization of mitigation sites by the valley elderberry longhorn beetle. For those sites where there was no potential introduction of the species via transplanted shrubs, one study found a 13.4 percent colonization rate for transplanted areas as compared to 2.3 percent for seedlings (Holyoak
et al.
2010, p. 49). As noted in this study, it can take approximately 7 years for elderberry shrubs to grow large enough to support the life-history requirements of the valley elderberry longhorn beetle, but monitoring is generally required only for 10-15 years (Holyoak
et al.
2010, p. 51). Thus, the observed low colonization rates are not unexpected, and the authors suggest that prescribed monitoring periods may not be of long enough duration for the species to find and use its host plant (Holyoak
et al.
2010, p. 51). The study found that the occupancy for the valley elderberry longhorn beetle was 43 percent for all sites through either introduction associated with transplanted elderberry shrubs or through colonization (Holyoak
et al.
2010, pp. 49-50). Overall, the conclusions from this study suggest that transplantation of elderberry is important for the species because the transplanted shrubs can contain the larval stage of the valley elderberry longhorn beetle or the shrubs are large
enough for the species to be able to recolonize areas within its range.
Small mitigation sites may not be of sufficient size to support recolonization of the valley elderberry longhorn beetle. The mitigation study conducted by Holyoak and Koch-Munz (2008, entire) highlighted the size differential between mitigation sites established for the valley elderberry longhorn beetle (mean 1.83 ac (1.74 ha) versus natural areas (mean 7.5 ac (3 ha)), and the authors concluded that the smaller sites established for mitigation are contributing to the habitat fragmentation for this species (Holyoak and Koch-Munz 2008, p. 452). The mitigation review by Holyoak
et al.
(2010, p. 51) also emphasized the importance of using transplants in reproducing populations of the valley elderberry longhorn beetle, and they recommended shrubs be transplanted to older mitigation sites that already contain elderberry plants of sufficient size such that the valley elderberry longhorn beetle species does not have to rely solely on transplanted shrubs for its survival. Holyoak
et al.
(2010, p. 49) reported that the valley elderberry longhorn beetle most frequently entered mitigation sites within elderberry shrubs that were transplanted from the site that was impacted. Their study found that the valley elderberry longhorn beetle was found at 28 percent of all mitigation sites, but at 88 percent of mitigation sites to which elderberry shrubs potentially containing valley elderberry longhorn beetles were transplanted; thus, only 16 percent of sites were colonized by the valley elderberry longhorn beetle on their own (Holyoak
et al.
2010, p. 51). In addition, Holyoak
et al.
(2010, p. 51) suggested using transplanted elderberry shrubs within (not between) watersheds to avoid disruption of potential genetic population structures. However, we are unaware of studies that have investigated valley elderberry longhorn beetle genetics between populations.
Perhaps more importantly, in addition to incorporating appropriate measures of size and appropriate elderberry characteristics in achieving successful occupancy of the valley elderberry longhorn beetle at restoration and mitigation sites, restoring natural riverine processes is also necessary to achieve functional restoration of remnant riparian ecosystems (e.g., Golet
et al.
2013, entire). Restoring riverine processes typically requires maintaining a hydrologic connection of floodplain areas with river systems and managing a flow regime for both ecological and human needs (Golet
et al.
2008, p. 20). The continued planting of seedlings or transplantation of shrubs at unsuitable mitigation or restoration sites is not only costly in resources, but represents a strategy that will likely not successfully achieve an elderberry shrub age class that provides a viable conservation value for the valley elderberry longhorn beetle and other wildlife.
Population Structure
The concepts of metapopulations, metapopulation theory, and the modeling of metapopulations have become increasingly useful tools for applying principles of landscape ecology to biological conservation. Metapopulations are defined as a system of discrete subpopulations that may exchange individuals through dispersal, migration, or human-mediated movement (Breininger
et al.
2002, p. 405; Nagelkerke
et al.
2002, p. 330). Metapopulation models can provide a way to analyze and predict the response of individual species to habitat fragmentation and other landscape elements (Beissinger
et al.
2006, p. 15).
The effects of spatial diversity (heterogeneity) on the distribution of the valley elderberry longhorn beetle were assessed using survey data collected at Central Valley study sites over 2 years (2002-2004) by Talley (2007, entire) that integrated patch (fine scale), gradient (broad scale), and hierarchical (mosaic of discrete multi-scale patches) spatial frameworks. The analysis revealed that a hierarchical spatial framework explained the most variance in the occupancy of the valley elderberry longhorn beetle (for the three river systems in which a spatial framework for the species was identified) (Talley 2007, p. 1484). However, an integrative approach of all three spatial frameworks (patch, gradient, and hierarchical) best defined a population structure for the valley elderberry longhorn beetle (Talley 2007, p. 1486). This population structure can be characterized as patchy-dynamic, with regional distributions made up of local aggregations of populations (Talley 2007, p. 1486). These localized populations are defined by both broad-scale or continuous factors associated with elderberry shrubs (e.g., shrub age or densities) and environmental variables associated with riparian ecosystems (e.g., elevation, associated trees) that themselves have patch, gradient, and hierarchical structures (Talley 2007, p. 1486).
Based on surveys conducted from 2002-2004, Talley (2005, pp. 25-26) concluded that the valley elderberry longhorn beetle vulnerable developmental stages (i.e., exposure of eggs and larvae) and its rarity (i.e., low local numbers, low occupancy) are important elements of the observed metapopulation structure of the species. Talley (2005, pp. 25-26) further concluded that large-scale catastrophic events and local changes in random processes or events (i.e., environmental stochasticity) have the potential to negatively affect riparian systems and, therefore, the species' vulnerability. Results from several other surveys of exit holes support the rarity traits such as low local numbers and low site-occupancy exhibited by the valley elderberry longhorn beetle:
(1) Estimates of occupancy, as measured by recent (new) exit hole observations
per elderberry groups
(or site), in the Central Valley were reported by Collinge
et al.
(2001, p. 105), based on surveys conducted in 1991 and 1997 (see Barr 1991, entire; Collinge
et al.
2001, entire). From these two surveys, Collinge
et al.
(2001, p. 105) estimated an occupancy rate of approximately 20 percent for both 1991 and 1997.
(2) A 2003 survey of planted elderberry shrubs (planted from 1993 to 2001) within restoration sites on the Sacramento River NWR found 0.6 to 7.9 percent shrubs contained exit holes (average per refuge unit) (River Partners 2004, pp. 2-3).
(3) A 2007-2008 survey of restoration sites within eight units of the Sacramento River NWR reported 21 percent occupancy based on observations of new exit holes (Gilbart 2009, p. 40).
(4) A 2010 survey of valley elderberry longhorn beetle exit holes within both elderberry shrubs and stems at 34 sites in 10 watersheds (American River to Tule River) determined the following occupancy (abundance) estimate information (Holyoak and Graves, 2010, entire; Holyoak and Graves 2010, Appendix 1):
• Forty-seven percent, or 16 of 34 sites, had new exit holes in elderberry shrubs.
• Ninety percent of the watersheds surveyed had new exit holes (elderberry stem or shrub).
• Sixteen percent, or a total of 71 new holes, were found out of a total of 441 elderberry shrubs surveyed (all sites).
(5) A June 2002 to September 2004 survey of a 14.9-mi (24-km) riparian corridor along the American River (lower American River Basin) estimated occupancy rates of the valley elderberry longhorn beetle ranging from 11.2 percent in lower alluvial plain, to 10.5 percent in mid-elevation riparian, to 8.7 percent in upper riparian terrace, to 2.9 percent in non-riparian scrub habitat (Talley
et al.
2007, pp. 25-26).
Although the surveys outlined above are not identical in their survey sites and sampling methods, the 16 percent abundance estimate from 2010 (new exit holes for all sites surveyed) and the 21 percent occupancy estimate from 2007 to 2008 (new exit holes from restoration sites at the Sacramento River NWR) (Gilbart 2009, p. 40) align closely with the 20 percent occupancy estimates for 1991 and 1997 presented in Collinge
et al.
(2001, p. 105).
Based on a spatial analysis of valley elderberry longhorn beetle populations in the Central Valley, Talley (2007, p. 1487) concluded that the several hundred meter (hundreds of feet) distances observed between local aggregations of the species supports a limited migration distance for this species, as noted above (see
Adult Behavior and Ecology
section). Talley (2007, p. 1487) further concluded that the clustering of valley elderberry longhorn beetle populations at smaller scales, tens of meters (tens of yards), is likely due to aggregation behaviors of this species, and is not the result of: (1) Environmental variables that occur at larger scales (less than 328 ft (less than 100 m), such as detection of elderberry plants (via plant volatiles); or (2) distances relevant to mate attraction, which occur at even smaller scales (few inches (centimeters)). However, additional studies of movement patterns are needed in order to better describe these observations of clustering and how these patterns relate to habitat availability (see
Adult Behavior and Ecology
section above).
Further support for the clustering or aggregations pattern of valley elderberry longhorn beetle populations can be found in colonization and extinction rates developed by Collinge
et al.
(2001, pp. 107-109) and Zisook (2007, p. 5). Collinge
et al.
(2001, p. 107) found in a comparison of 1991 and 1997 surveys of both old and recent exit holes in 14 drainages (65 sites, 111 groups of elderberry shrubs), that two sites (6.5 percent) had
long-term
extinctions (i.e., no holes found in 1997 and exit holes of any age observed in 1991) and four sites (12.9 percent) had
long-term
colonizations (i.e., recent exit holes observed in 1997, but no exit holes of any age found in 1991). The comparative study also described short-term events (extinctions and colonizations) based only on observations of recent exit holes for both survey years. Nine sites (29 percent) exhibited
short-term
extinctions and six sites (19.4 percent) had
short-term
colonizations (Collinge
et al.
2001, p. 108). One area (near Black Butte Lake; Stony Creek drainage) that was occupied in 1991 was found to be unoccupied in the 1997 survey (Collinge
et al.
2001, p. 108). The study concluded, based on observations of only recent exit holes, that 77 percent of the sites had the same occupancy status for the 2 years, with 23 percent of sites showing some turnover between the two surveys (Collinge
et al.
2001, p. 108). Zisook (2007, entire) presented an unpublished analysis of extinction and colonization rates for the valley elderberry longhorn beetle based on elderberry shrub sampling along a 14.9-mi (24-km) section of the Lower American River. The analysis compares the 2000 to 2004 surveys to re-sampling efforts in 2005. In this study, extinction was defined when no new (recent) holes were found on the same shrub in 2005 but where any age holes were recorded in 2000-2004; a colonization event was recorded when there were no new holes found on a shrub in 2000-2004, but a recent hole was found on the same shrub in 2005 (Zisook 2007, p. 4). The analysis estimated an extinction rate of about 57 percent and a colonization rate of 19.1 percent for the population sampled (Zisook 2007, p. 3).
These evaluations suggest that occupied sites of the valley elderberry longhorn beetle tend to remain occupied (i.e., 77 percent), but also exhibit variable long-term extinction rates (between 6.5 to 57 percent), and slightly higher short-term extinction rates. These occupancy patterns result in a local clustering or aggregations of regional, but patchy, populations within its range. We caution that these extinction evaluations/results are from short-term studies at different locations; therefore, these rates may not be suitable to illustrate past or current conditions, especially for areas that have not been recently surveyed for occupancy or colonization.
Rangewide surveys that utilize recent (new) exit holes as a measure of valley elderberry longhorn beetle occupancy continue to be challenging, given the species' low population densities and wide, but discontinuous distribution. Monitoring methods for valley elderberry longhorn beetle sites were evaluated from surveys conducted in 2010 at 10 watersheds (34 sites), from Shasta County to Kern County (Holyoak and Graves 2010, entire). The study determined that an occupancy rate of 1.5 percent of elderberry stems and a sample size of at least 600 elderberry stems for each watershed was needed to detect large (50 to 80 percent) declines in populations of the valley elderberry longhorn beetle, a condition not met in many areas of the Central Valley (Holyoak and Graves 2010, p. 2). However, using a sampling rate of 500 elderberry stems and 50 elderberry shrubs per watershed, the study found that a good estimate of population density (based on the number of new exit holes present) could be determined for 4 of the 10 watersheds surveyed (or 23 of 34 sites) (Holyoak and Graves 2010, p. 2). The authors recommended that a monitoring program for the valley elderberry longhorn beetle in the Central Valley include a core group of sites with the necessary number of elderberry stems to determine occupancy, in combination with sampling other watershed locations for presence or absence of new exit holes rather than abundance (Holyoak and Graves 2010, p. 20).
Pheromone traps using aggregation pheromones (male-produced sex attractants) (see, for example, Lacey
et al.
2004, entire) may provide an important survey tool for future distribution or taxonomic studies. In April 2013, after the proposed rule published, field trials were conducted at a riparian forest restoration site within the Sacramento River NWR to test the efficacy of synthesized female valley elderberry longhorn beetle sex pheromone (Arnold 2013, entire). Male valley elderberry longhorn beetles were attracted almost exclusively to traps baited with the (
R
)-desmolactone sex pheromone (33 of 34 males captured); no female adult beetles were found in the traps (Arnold 2013, p. 4). This pheromone has also been found (under laboratory conditions and in the field) to be an attractant for male California elderberry longhorn beetles in San Bernardino County (Ray
et al.
2012, pp. 163-164). In both studies, no other cerambycid species were caught in traps baited with either (
R
)- or (
S
)-desmolactone, which suggests that (
R
)-desmolactone may be a pheromone specific to only these two subspecies (Ray
et al.
2012, p. 166; Arnold 2013, p. 4). Observations of male beetles (confirmed through their sexually dimorphic characteristics) attracted to these traps could also be used to confirm the taxonomic identity of the valley elderberry longhorn beetle where the two subspecies may co-occur (Arnold 2013, p. 4).
Vulnerability Factors
Collinge
et al.
(2001, p. 111) described the observed distribution and abundance pattern of the valley elderberry longhorn beetle as an unusual type of rarity, with small and localized populations where it occurs within its presumed historical range. Rare species are generally considered more vulnerable to extinction than
common species (Sodhi
et al.
2009, p. 517). In general, three criteria of rarity can be used to evaluate a species' vulnerability to extinction risk when applied to its entire geographic range or to its distribution and abundance in a specific area: (1) Narrow geographic range; (2) specific habitat requirements; and (3) small population size, although within a limited geographical range, a rare species may be locally abundant (Primack 2006, pp. 155-156).
There is not always a consistent relationship between rarity and extinction risk resulting from human influences, since the risk of extinction is a function of more complex interrelationships between the ecology of a species, its life history, and human activities (Pullin 2002, pp. 199-200). Nevertheless, vulnerability measures (e.g., Kattan index (Kattan 1992, entire)) have been shown to be good proxies for extinction risk, as observed for a study of beetles in an Italian region of the Mediterranean (Fattorini 2013, p. 174).
The valley elderberry longhorn beetle exhibits several life-history traits that may limit its distribution and population growth, which can provide an extinction vulnerability profile. These attributes include:
(1) Restriction of the species to specific host plant taxa within the Central Valley of California (i.e., specialized niche).
(2) Dependence on riparian ecosystems that have been reduced in size and modified by human activities.
(3) Locally clustered populations with limited dispersal ability that can be affected by natural and human disturbances.
All of these attributes, but particularly habitat specificity, represent vulnerabilities for the valley elderberry longhorn beetle. Vulnerability to extinction can be further complicated by the effects of a changing climate. Numerous traits associated with climate change vulnerability have been identified and consolidated into trait sets by Foden
et al.
(2013, entire), based on a global assessment of bird, amphibian, and coral species. Although the trait sets were not specific to insect taxa, they are similar to variables considered in climate change vulnerability assessment indices for vertebrate species (Bagne
et al.
2011, entire) and for plant and animal species (Glick
et al.
2011, pp. 40-43, 48-50; Young
et al.
2011, entire). The trait sets are as follows: specialized habitat and/or microhabitat specialization; narrow environmental tolerances; potential for disruption of environmental triggers if they are important aspects in the life cycle; disruption of important interspecific interactions; rarity; poor dispersal potential due to low inherent dispersal ability and/or extrinsic barriers to dispersal; and poor micro-evolutionary potential due to low genetic diversity, long generation lengths and/or low reproductive output (Foden
et al.
2013, e65427). In addition to the effect of any one trait, interactions between life history and spatial traits also can influence extinction risk due to climate change (Pearson
et al.
2014, entire; Guisan 2014, entire).
Vulnerabilities may separately, or together, exacerbate the risk of the threats described below in the Summary of Factors Affecting the Species section.
Population Viability Analysis
Greenberg (2009, entire) developed a population viability analysis (PVA) for the valley elderberry longhorn beetle using, in part, demographic information provided from personal communications from previous researchers. A metapopulation model was constructed to examine how the spatial arrangement of habitat, dispersal range of adults, and regulation of local populations (density dependence) based on age structure affect the persistence of the valley elderberry longhorn beetle. The results of this PVA model provide useful insights into how the number and configuration of patches affect population persistence and highlight the need to better understand migration distance between patches (Greenberg 2009, p. 55). However, the predictions of population persistence probabilities for this limited PVA analysis should be used with caution given the incomplete empirical information and choice of parameter values used in constructing this particular model. In addition, this model did not incorporate potential effects related to climate change. Thus, in this withdrawal, we do not provide additional discussion of this PVA (and note this analysis has not been peer reviewed); however, we anticipate using this modeling tool to help direct future management options.
Summary
When we consider the low estimates of occupancy (Talley
et al.
2007, pp. 25-26) and observed extinction and colonization patterns (Collinge
et al.,
2001, pp. 107-108; Zisook 2007, p. 5), combined with our re-evaluation of available data sets describing the distribution of observations over the past 16 years (since 1997) (see Table 1, Figure 2), it is apparent that the distribution and abundance of the valley elderberry longhorn beetle is clustered in regional aggregations and locally uncommon or rare, which is consistent with our understanding of its rare, patchy distribution pattern across its presumed historical range in the Central Valley. Although evidence of occupancy (primarily observations of exit holes) for the species has been documented in additional locations to those recorded at the time of listing in 1980, the best available data indicate this is a result of limited data available at the time of listing and the subsequent surveys conducted in: (1) The late 1980s (Jones and Stokes 1987, entire); (2) 1991 (Barr 1991, entire); (3) 1997 (Collinge
et al.
2001, entire); (4) 2002-2005 (Talley 2014a, pers. comm.); and (5) 2010 (Holyoak and Graves 2010, entire). These surveys have better defined the presumed historical range of both elderberry longhorn beetles found in California (see also Chemsak 2005, pp. 6-7; Figure 1, above). Additional comprehensive surveys within the Central Valley, particularly locations of adult male beetles, and the development of long-term population data sets for this species are needed in order to provide a more complete assessment of current population size and distribution.
As noted above, the valley elderberry longhorn beetle exhibits several attributes that may limit its distribution and population size. These include small numbers in localized populations, low estimates of occupancy within its range (see
Population Structure
discussion), limited dispersal, and dependence on two host plants for its entire life cycle that are currently found within ecological communities that have been reduced, fragmented, or otherwise degraded through human-caused alterations. These attributes, particularly habitat specificity (i.e., increased specialization), represent important vulnerabilities for the valley elderberry longhorn beetle, that separately, or together, may exacerbate any of the threats described below in our five-factor analysis. Furthermore, environmental factors (e.g., additional habitat loss, unfavorable hydrological conditions) or other types of stressors (e.g., predation) are likely to significantly influence the species' vulnerability to extinction (see Summary of Factors Affecting the Species discussions below).
Summary of Factors Affecting the Species
Section 4 of the Act and its implementing regulations (50 CFR part 424) set forth the procedures for adding species to the Federal Lists of Endangered and Threatened Wildlife and Plants. A species may be determined to be an endangered species
or threatened species because of one or more of the five factors described in section 4(a)(1) of the Act: (A) The present or threatened destruction, modification, or curtailment of its habitat or range; (B) overutilization for commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) the inadequacy of existing regulatory mechanisms; or (E) other natural or manmade factors affecting its continued existence. Listing actions may be warranted based on any of the above threat factors, singly or in combination. Each of these factors is discussed below.
The five factors listed under section 4(a)(1) of the Act and their analysis in relation to the valley elderberry longhorn beetle are presented below. This analysis of threats requires an evaluation of both the threats currently facing the species and the threats that could potentially affect it in the foreseeable future. The Act defines an endangered species as a species that is in danger of extinction throughout all or a significant portion of its range (16 U.S.C. 1632(6)). A threatened species is one that is likely to become an endangered species in the foreseeable future throughout all or a significant portion of its range (16 U.S.C. 1632(20)).
In considering what factors might constitute threats, we must look beyond the exposure of the species to a particular factor to evaluate whether the species may respond to the factor in a way that causes actual impacts to the species. If there is exposure to a factor and the species responds negatively, the factor may be a threat, and during the status review, we attempt to determine how significant a threat it is. The threat is significant if it drives or contributes to the risk of extinction of the species, such that the species warrants listing as endangered or threatened as those terms are defined by the Act. However, the identification of factors that could impact a species negatively may not be sufficient to compel a finding that the species warrants listing. The information must include evidence sufficient to suggest that the potential threat is likely to materialize and that it has the capacity (i.e., it should be of sufficient magnitude and extent) to affect the species' status such that it meets the definition of endangered or threatened under the Act.
The information presented in the five-factor analysis in this withdrawal differs from that presented in the proposed rule. Specifically, we restructured the five-factor analysis from our proposed rule (77 FR 60238; October 2, 2012) to reflect our reanalysis of threats, including additional and more detailed information (e.g., invasive plants in
Factor A
and pesticides under
Factor E
). We provide a more extensive discussion of effects related to climate change in our analysis of threats (under
Factors A
and
E
), including incorporation of predictions from several regional climate models for the Central Valley region. We also incorporate detailed results of several studies (e.g., metapopulation analysis) and use this information to evaluate the current threats to the species. We also reiterate our discussion contained in the proposed rule of small population size under
Factor E,
but do not include in this withdrawal an evaluation of loss of populations resulting from habitat fragmentation because we find that additional data are needed to adequately or appropriately assess this threat. Threats related to the effects of pruning, briefly mentioned in our proposed rule under a
Factor E
threat (Human Use) (77 FR 60263; October 2, 2012), are discussed in this withdrawal under
Factor A.
Factor A. The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range
Historical Loss of Riparian Ecosystems
In our final rule listing the valley elderberry longhorn beetle as threatened and designating critical habitat (45 FR 52803; August 8, 1980), we identified loss of habitat as a significant impact to the valley elderberry longhorn beetle due to the threats of agriculture conversion, levee construction, and stream channelization within its “former” range. In our proposed rule to delist the valley elderberry longhorn beetle (77 FR 60250; October 2, 2012), we reviewed the impacts, or potential impacts, of agricultural and urban development to the species, primarily in the context of the loss of riparian vegetation in the Central Valley, as well as impacts, or potential impacts, related to the effects of levee construction and other flood protection measures, and road maintenance and dust. In this withdrawal, we provide a revised description of the impact of habitat loss to the valley elderberry longhorn beetle based on our analysis of recently mapped elderberry habitat within the Central Valley (Service 2014, GIS analysis), in conjunction with new discussion related to the success of restoration and mitigation sites intended to provide habitat for the species. Similar to the proposed rule (77 FR 60250-60258; October 2, 2012), we also include separate discussions for
Factor A
threats that may result in the destruction or modification of habitat (i.e., levee and flood protection infrastructure, road and trail use and maintenance, pruning, effects of climate change, and invasive plants). Additionally, we note that pruning was only briefly discussed in the proposed rule under
Factor E—
Human Use; we have expanded that discussion and are now including it under
Factor A
because we consider pruning activities to be a potential threat related to destruction or modification of habitat.
Loss of habitat is the leading cause of species extinction (Pimm and Raven 2000, p. 843). Insects that are considered specialized plant-feeders or those restricted to one (monophagous) or a few (oligophagous) plant taxa are especially vulnerable to habitat loss, as their survival may depend on their ability to make improbable or impossible host plant shifts (Fonseca 2009, p. 1508). The valley elderberry longhorn beetle can be considered an oligophage, and is dependent exclusively on two elderberry taxa (see Habitat section) for all aspects of its life history.
Prior to settlement by Anglo-Americans, the Central Valley contained extensive riparian plant communities along unaltered river systems, including riparian forests comprised primarily of sycamore, cottonwood, willow, and oak trees and a thick understory of shrubs, including elderberry (Roberts
et al.
1980, pp. 7, 10). A detailed summary of historical observations (circa 1800s) of riparian forests along the Sacramento River is presented in Thompson (1961, pp. 301-307). The majority of this “timber belt” was cut as early as 1868 (Tehama County) to supply fuel and timber (e.g., fencing) as the valley was settled (Thompson 1961, p. 311). In addition to supplying lumber to a largely treeless valley, the trees that comprised the historic riparian forests of the Sacramento Valley (and likely other parts of the Central Valley) provided reinforcement to river banks and greater stability to stream channels (Thompson 1961, p. 315). These forests also served as windbreaks, reducing the effects of wind and evapotranspiration, while providing important wildlife habitat (Thompson 1961, p. 315).
Much of the historically occurring riparian forests were lost in the Central Valley prior to the listing of the valley elderberry longhorn beetle (see summary for the Sacramento Valley by Thompson 1961, pp. 310-315). Katibah (1984, pp. 27-28) estimated approximately 102,000 ac (41,300 ha) of riparian forest remained in the Central Valley in 1984, a reduction of about 89 percent from an estimated total of 921,600 ac (373,100 ha) of pre-
settlement riparian forest area. A Central Valley mapping effort, initiated in 1978 with legislation that provided funding to study the riparian resources of the Central Valley and desert (Riparian Mapping Team 1979, p. 1), presented an initial evaluation of the condition of riparian vegetation using remote sensing methods in 1981 (Katibah
et al.
1981, entire; see also Katibah
et al.
1984, entire), or 1 year after the listing of the valley elderberry longhorn beetle as threatened (45 FR 52803; August 8, 1980). This assessment used a qualitative condition index for each sample site and concluded that the conditions of riparian systems at that time were either disturbed, degraded, or severely degraded (85 percent), with 15 percent considered to be in good or “apparently unaltered” condition (Katibah
et al.
1981, p. 245). About 34 percent of riparian systems were considered to be recovering or stable (Katibah
et al.
1981, p. 245). Adjacent land uses (primarily agriculture), stream channelization, and livestock grazing were reported as important negative influences on riparian systems (Katibah
et al.
1981, p. 244). Specifically, artificial levees, river channelization, dams, and water diversions were identified as factors in reducing the original riparian forests to the remnant habitat described at that time for the Central Valley (Katibah 1984, p. 28).
Since that initial assessment, the Central Valley Historic Mapping Project has refined their estimates of historic natural vegetation for the Central Valley and has developed an accessible GIS-based analysis of vegetation changes over the past 100 years (Geographical Information Center (GIC) 2003, entire). Four maps (pre-1900, 1945, 1960, 1995) were created to illustrate eras in which significant land use changes occurred in the Central Valley, such as Anglo-American settlement and water diversion projects (GIC 2003, p. 3). Using a variety of methods and sources, this analysis estimated that 1,021,584 ac (413,420 ha) of riparian vegetation were found within the valley pre-1900, and about 132,586 ac (53,656 ha) of riparian vegetation remained in the Greater Central Valley in 2000, a reduction of 87 percent (GIC 2003, p. 14).
Based on results from a 2003 survey of 16 waterways (47 plots) in the Sacramento Valley (i.e., upper portion of the extant occurrences observed for the valley elderberry longhorn beetle), Hunter
et al.
(2003, p. 41) described the riparian vegetation along these waterways as “relatively narrow bands with an open, discontinuous canopy.” This survey described many of these riparian zones as disturbed, with evidence of channel incision, overbank flows, and dumping of trimmed/cut tree branches, and they frequently contained some type of infrastructure (Hunter
et al.
2003, p. 41). Surrounding land use (within 820 ft (250 m)) was characterized as 43 percent natural, 38 percent agricultural, and 18 percent developed; only 17 percent of the plots were surrounded entirely by natural vegetation (Hunter
et al.
2003, p. 41).
The Sacramento River represents one river system in the Central Valley within the northern range of the valley elderberry longhorn beetle that has been severely degraded through channelization, bank protection (e.g., levees and riprap), and effects related to the construction of the Shasta Dam and other foothill storage reservoirs (Golet
et al.
2013, p. 3). Natural, but fragmented, habitats (e.g., riparian, grasslands, sloughs, and valley oak woodlands) remain along the Sacramento River (Golet
et al.
2013, p. 5). The middle section of the river (Red Bluff to Colusa) has been the focus of restoration efforts following the passage of State legislation in 1986 (Senate Bill 1086), which mandated the development of a management plan to protect, restore, and enhance riparian vegetation along the river (Sacramento River Conservation Area Forum 2003, p. v). A comprehensive evaluation of the success of these efforts indicated that, while progress has been made in achieving goals related to plant species and communities (including an increase in elderberry shrubs) and some wildlife taxa, progress towards restoring stream flows and natural floodplain and flood processes has been poor (Golet
et al.
2013, pp. 19-21). In addition, this evaluation found that the status of natural riverine habitats in this portion of the Sacramento River was, in general, poor and declining, which was attributed to continued human alterations that constrain the river's hydrologic and geomorphic processes (Golet
et al.
2013, p. 22). One of the major factors identified as responsible for the continued degradation of riverine habitats was the installation of riprap, which the study indicated has been steadily increasing along the Sacramento River since the 1930s (Golet
et al.
2013, p. 22).
Assessment of Current Elderberry Habitat Relative to Metapopulation Structure of the Valley Elderberry Longhorn Beetle
As part of the Central Valley Flood protection efforts, Chico State University, the GIC, and CDFW's Vegetation Classification and Mapping Program have developed both a medium-scale and fine-scale dataset for riparian vegetation in the Central Valley (CDWR 2012b, pp. 5-1—5-9). The medium-scale map illustrates the extent of riparian vegetation using about 20 general vegetation classes (see CDFW 2014a and Central Valley Riparian Mapping Project (CVRMP) 2014 for Web site addresses). The fine-scale version provides a more detailed plant community resolution such that vegetation associations and alliances containing a range of probability of elderberry shrub occurrence within those associations and alliances can be identified; this map is nearly complete for the entire Central Valley. Both maps were created using imagery from the U.S. Department of Agriculture (USDA) National Agriculture Imagery Program (NAIP) from 2009 and current field sampling (USDA NAIP 2014).
In our proposed rule, we presented an estimate of 46,936 ac (18,994 ha) of protected riparian vegetation, which we stated may or may not contain elderberry shrubs (77 FR 60256, October 2, 2012). Rather than infer the amount of elderberry habitat from this gross estimate of riparian vegetation (which is what was presented in the proposed rule), we instead use the mapped
Sambucus nigra
Alliances (described as blue elderberry) defined in the 2009 Central Valley fine-scale riparian vegetation data set (CDFW and GIC 2013) to better define the current extent of elderberry habitat in the Central Valley. We also assess the size of the defined polygons of elderberry and their location in the Central Valley relative to the presumed metapopulation structure identified for the valley elderberry longhorn beetle (Talley
et al.
2006a, pp. 10-11). We acknowledge that elderberry shrubs likely occur in varying degrees of cover and constancy within other mapped vegetation alliances, but we are unable to accurately determine the extent and location of these areas based on the spatial information in these data sets and descriptions provided in Buck-Diaz
et al.
(2012, Appendix 4) for these other plant alliances; thus, our estimate of elderberry habitat is likely to be conservative.
The CDFW/GIC data set contains 39 blue elderberry polygons (124 ac (50 ha)) located within our presumed historical range for the valley elderberry longhorn beetle (see Figure 1). Using the metapopulation spatial parameters presented in Talley
et al.
(2006a, p. 11) (i.e., extent of 1,968-2,625 ft (600-800 m) defined as a cluster), we identified potential metapopulation clusters in our data set. We first determined which of the mapped elderberry polygons were less than 1,968 ft (600 m) from their
nearest neighbor (16 of the 39 polygons), and merged these together to redefine these larger polygons. This resulted in 16 polygons merging into 4, for a new total of 27 mapped elderberry polygons. We then conducted a “bounding containers” GIS analysis (Service 2014, GIS analysis) for these 27 polygons to identify those (now rectangular) polygons where the diagonal was at least 1,968 ft (600 m), as this is the minimum distance (i.e., 1,968-2,625 ft (600-800 m)) to meet Talley
et al.'
s (2006a, p. 11) criteria as a metapopulation cluster.
Based on this analysis, 3 of the 27 polygons had a longest length (i.e., diagonal) greater than 1,968 ft (600 m) and, therefore, could be considered as metapopulation clusters supporting a regional population of the valley elderberry longhorn beetle (Talley
et al.
2006a, p. 11). These three elderberry clusters were located: (1) Along the Cosumnes River; (2) south of Marysville at the southern end of Clark's Slough; and (3) near an unnamed tributary of the Yuba River. All other mapped elderberry polygons were less than 1,968 ft (600 m) in extent.
We then evaluated the location of exit holes or beetle observations from 1997 to 2012 (Figure 2) relative to all 39 elderberry polygons. Based on the level of precision of the mapped locations, we find that 38 survey points out of a total of 1,422 (or less than 3 percent) were located within the 39 elderberry polygons.
These results could be interpreted in several ways (or in combination): (1) Relatively few stands of elderberry habitat remain within the Central Valley and their small size (average of 2.9 ac (1.17 ha)) and spatial arrangement may be insufficient to support the metapopulation structure defined for the valley elderberry longhorn beetle (Talley
et al.
2006a, p. 11); (2) areas within the species' range have not been adequately surveyed; (3) the mapping methods used did not identify all areas of elderberry habitat; or (4) the parameters that define the presumed metapopulation structure or the life-history requirements for the species need to be reevaluated. Occupancy surveys within the mapped elderberry polygons are needed to assess these or other possibilities.
Occupancy of Restoration and Mitigation Sites
As noted in our proposed rule (77 FR 60256-60258; October 2, 2012), efforts to establish areas of riparian vegetation (though not necessarily elderberry habitat) through restoration projects or mitigation requirements under the Act have been conducted in order to provide additional areas of habitat for the species. Rather than present rough estimates of the number of acres of protected riparian vegetation, as was done in the proposed rule, we are instead providing in this document a review of assessments of these areas conducted in the past 10 years. We modified this discussion from what was presented in the proposed rule based on comments received, as well as evaluated the success of some of these restoration and mitigation sites based on estimates of occupancy of the valley elderberry longhorn beetle.
An evaluation of restoration of riparian vegetation along 106 river km (66 river mi) of the Sacramento River included an assessment of valley elderberry longhorn beetle occupancy (exit holes) at five restoration sites (surveys conducted in 2003) (Golet
et al.
2008, pp. 7-8). Older restoration sites (greater than 8 years) had a larger percentage (approximately 10 to 21 percent) of shrubs with exit holes (River Partners 2004, p. 3), likely due to the size class differential and observed preferences of the valley elderberry longhorn beetle for larger stem sizes.
A limited evaluation of (blue) elderberry and other riparian planting efforts at 30 mitigation sites over approximately 485 ac (196 ha) in the Central Valley (from Tehama County to Madera County) was undertaken in 2005 and 2006 to evaluate their success in establishing occupancy of the valley elderberry longhorn beetles (Holyoak and Koch-Munz 2008, entire). A spatial analysis of exit holes of all ages determined that the valley elderberry longhorn beetle was present at 16 of the 30 mitigation sites (53 percent) (Holyoak and Koch-Munz 2008, p. 447). As noted above, the abundance of the valley elderberry longhorn beetle per elderberry shrub and per stem in this study was also found to be positively related to the age of the mitigation site (Holyoak and Koch-Munz 2008, p. 449).
Holyoak
et al.
(2010, entire) reviewed publicly available mitigation monitoring reports (total of 60) to evaluate the success of mitigation sites in conserving the valley elderberry longhorn beetle, as measured by the survival of elderberry plants and how frequently the species colonized mitigation sites. Although this review noted that many expected mitigation reports were missing and thus highlighted the need for better data management practices, they found that the survival of both elderberry seedlings and transplants was highly variable and declined over time after planting (Holyoak
et al.
2010, p. 48). Specifically, by year seven, 57 to 64 percent of transplanted elderberry survived, with 71 percent survival of seedlings (Holyoak
et al.
2010, pp. 48-49). The study also found that the mitigation site (e.g., location, age) accounted for 25 percent of the variability in proportion of seedlings that survived, which suggested that the mitigation site choice can have an important effect on the ability to establish elderberry plants (Holyoak
et al.
2010, p. 49).
Summary of Available Habitat
There has been a significant loss and degradation of riparian and other natural habitats in the presumed historical range of the valley elderberry longhorn beetle, much of which occurred prior to the listing of the species. In our proposed rule, we noted that we could not accurately determine the potential lost historical range of valley elderberry longhorn beetle habitat, and that coarse estimates have been attempted based on historical losses of riparian vegetation (77 FR 60241; October 2, 2012). Rather than infer lost elderberry habitat from estimates of lost riparian forests, we include here a summary of current elderberry habitat (based on 2009 imagery) mapped within the Central Valley, and assess how these mapped areas conform to the metapopulation structure of the valley elderberry longhorn beetle as defined by species' experts. This preliminary assessment indicates that elderberry habitat remains limited in extent within the Central Valley and may not support the spatial requirements of sustainable metapopulations presumed for the valley elderberry longhorn beetle. We note that the results of this assessment do not allow us to draw definitive conclusions on the valley elderberry longhorn beetle metapopulation given the limitations of these data.
Occupancy rates of valley elderberry longhorn beetle in riparian vegetation at some mitigation sites provide some indication that the species has been successful in colonizing these areas; however, monitoring is incomplete in both these areas and within restoration sites. Given the life-history traits defined for the valley elderberry longhorn beetle, as discussed in the Background section (i.e., habitat specialist, with limited mobility and a short adult life span, and low local numbers within a population structure), and the limited and fragmented habitat within its current range, we reaffirm our conclusion in the proposed rule that loss of habitat continues to remain a threat to the species. For this withdrawal, we reevaluated this threat in combination with the other threats
described below and determined threats to the species and its habitat have not been reduced such that delisting is appropriate.
Levee and Flood Protection Infrastructure
As described in our proposed rule, the Central Valley contains an extensive flood protection system, much of which predates the listing of the valley elderberry longhorn beetle (77 FR 60251; October 2, 2012). The (California) State Plan of Flood Control (SPFC) represents a portion of the Central Valley flood management system for which the State has special responsibilities, as described in the California Water Code Section 9110(f) (CDWR 2011, pp. 1-7). The SPFC Descriptive Document provides a detailed inventory and description of the levees (approximately 1,600 mi (2,575 km)), weirs, bypass channels, pumps, dams, and other structures included in the SPFC (CDWR 2010, entire). This flood protection system comprises federally and State-authorized projects for which the Central Valley Flood Protection Board or the California Department of Water Resources (CDWR) has provided assurances of cooperation to the Federal Government. Other flood protection facilities in the Sacramento River and San Joaquin River watersheds that are not covered by these assurances are not part of this State-Federal system (CDWR 2010, p. Guide-1). Thus, the SPFC represents a portion of the larger system that provides flood protection for the Central Valley (CDWR 2010, p. Guide-1).
As noted in the proposed rule, ongoing and future maintenance of these flood protection elements may result in losses of riparian vegetation and elderberry shrubs in addition to what has been historically lost; however, we stated that we had no estimate of the acreage of riparian vegetation (or elderberry shrubs within these areas) on the flood protection levees or lands that provide additional flood facilities (77 FR 60252; October 2, 2012).
We also described in our proposed rule new flood control system maintenance requirements being implemented by the U.S. Army Corps of Engineers (Corps), specifically, the 2009
Guidelines for Landscape Planting and Vegetation Management at Levees, Floodwalls, Embankment Dams, and Appurtenant Structures
(Engineering Technical Letter (ETL) 1110-2-571) (Corps 2009, entire). In general, this ETL establishes a vegetation-free zone for the top of all levees and levee slopes, and 15 ft (4.5 m) on both the water and land sides of levees (Corps 2009, pp. 2-1—2-2, 6-1—6-2), which are practices that could eliminate occupied or unoccupied elderberry shrubs. On April 30, 2014, the Corps issued a new
Guidelines for Landscape Planting and Vegetation Management at Levees, Floodwalls, Embankment Dams, and Appurtenant Structures
(ETL) 1110-2-583), superseding the 2009 ETL (Corps 2014, entire). The 2014 guidelines maintains the previous ETL guidelines of a vegetation-free zone for the top of all levees and levee slopes, and 15 ft (4.5 m) on both the water and land sides of levees (Corps 2014, pp. 2-1—2-3, A2-A3).
At the time of our proposed rule, we indicated that the final policy guidance for the issuance of variances from the ETL vegetation standards for levees and floodwalls had not been released; therefore, we were unable to determine if this variance process would have an effect on levee segments containing woody vegetation (77 FR 60253; October 2, 2012). In this document, we provide an update to our discussion of this threat and include additional information relative to policies being implemented by CDWR to address levee vegetation management.
On February 17, 2012 (77 FR 9637), the Corps issued a notice for a Policy Guidance Letter (PGL) outlining the process for requesting this variance. The PGL applies to levees within the Corps' Levee Safety Program including those operated or maintained by the Corps, those that are federally authorized and locally operated and maintained, and those locally constructed and locally operated and maintained, but associated with the Corps' Rehabilitation and Inspection Program (77 FR 9637; February 17, 2012). However, in practice, the variance process has been described as time intensive and costly, even for just a few miles of levee (Qualley 2014, pers. comm.). Therefore, securing variances for the protection of elderberry shrubs or other riparian vegetation found on levees under the Corps' jurisdiction may not be a practical option at this time.
The CDWR's Central Valley Flood Protection Plan (CVFPP) includes a Levee Vegetation Management Strategy to address the vegetation-free guidelines set out within the Corps' ETL (CDWR 2011, pp. 4-13—4-16). The approach states that it “reflects a flexible and adaptive management strategy that meets public safety goals, and protects and enhances sensitive habitats in the Central Valley” (CDWR 2012a, p. 1). Specifically, new levees would be constructed and managed consistent with the new policy, however, those levees with “legacy” trees would be managed to allow existing large trees and other woody vegetation to continue their normal life cycle unless they were considered to be an unacceptable threat to levee integrity (CDWR 2012a, p. 1). The CVFPP strategy also allows for the retention of waterside vegetation below the vegetation management zone (generally beyond the 20-ft (6.1-m) slope length from the levee crown) (CDWR 2011, p. 4-14). This CVFPP strategy is likely to provide, at least in the short term, a more protective mechanism for riparian vegetation, including elderberry shrubs, than the variance process outlined in the PGL (which as stated above is intensive, costly, and likely not practical).
The potential for the Corps to issue variances under the ETL guidance along with CDWR's strategy to address levee vegetation management do not change CDWR's obligation to meet Federal and State law with regard to valley elderberry longhorn beetle habitat and riparian vegetation (see
Factor D
) (Qualley 2014, pers. comm.).
The Water Resources Reform and Development Act (WRRDA) of 2014 (Pub. L. 113-121) contains a vegetation management policy provision (Title III, Subtitle B-Levee Safety, Section 3013) that requires the Corps to conduct a comprehensive review of its policy guidelines (i.e., ETL 1110-2-583 and PGL for requesting variances, as noted above) for management of vegetation on levees in consultation with other applicable Federal agencies, representatives of State, regional, local, and tribal governments, appropriate nongovernmental organizations, and the public. This may allow for more appropriate regional variances from the single national ETL standard currently outlined in the Corps' vegetation management policies. The WRRDA 2014 vegetation management policy provision also includes a requirement for the Corps to solicit and consider the views of independent experts on the engineering, environmental, and institutional considerations underlying the guidelines.
In summary, as we concluded in our proposed rule (77 FR 60254; October 2, 2012) and reaffirm in this document, levee vegetation management actions are expected to continue to impact elderberry shrubs within the range of the valley elderberry longhorn beetle. Threats related to removal of elderberry vegetation may be reduced in the future in some locations within the Central Valley based on revisions to the Corps' vegetation management policies as outlined in the 2014 WRRDA. Long-
term impacts of levee vegetation management actions may be offset with implementation of mitigation (e.g., establishment of mitigation sites or restrictions on pruning); however, as described above and in our Background section, the success of mitigation sites in establishing occupancy of the valley elderberry longhorn beetle has not been fully evaluated, so its success is currently indeterminable.
Road and Trail Use and Their Maintenance
Road and trail use and their maintenance and the effects of dust related to these activities are identified in our Recovery Plan and in Biological Opinions as threats to the quality of valley elderberry longhorn beetle habitat (Service 1984, p. 41; Service 2002, p. 3). As described in our proposed rule, machinery used in road maintenance activities can crush adjacent elderberry shrubs, or cause indirect stress to plants (e.g., leaf shading, blocked stomata) through the raising of dust (77 FR 60254; October 2, 2012). Similarly, dust can originate from access roads and recreational trails within riparian corridors where elderberry habitat is often found (Talley
et al.
2006b, p. 648). Dust could also affect the survival and behavior of the valley elderberry longhorn beetle by smothering adults or larvae, disrupting chemical cues important for mating and detecting host plants, or creating unpalatable leaves or flowers (Talley
et al.
2006b, p. 649).
As noted in our proposed rule (77 FR 60254, October 2, 2012), a rangewide study on the effects of dust to the valley elderberry longhorn beetle or its host plant has not been conducted. To better address this topic, we provide a summary of a study that evaluated dust effects that was not described in the proposed rule.
A study to test the effects of dust from dirt trails relative to paved trails was conducted along the American River Parkway in 2003 (Talley
et al.
2006b, entire). The study found similar dust settlement rates and leaf dust accumulation along dirt and paved trails, but when data from all sites were pooled, elderberry plants tended to be more stressed (e.g., shorter plants, lower percent leaf water content, thicker leaves, higher percentage of dead stems) near dirt trails than paved surfaces (Talley
et al.
2006b, p. 651), a result the authors attributed to factors other than dust (Talley
et al.
2006b, p. 653). Talley
et al.
(2006b, p. 653) concluded the difference in elderberry characteristics near dirt trails was likely due to reduced water availability (less surface runoff than near paved surfaces) and less soil water (further distances from water sources). The authors also suggested that the effects of dust may be more significant over larger spatial scales given the variability of dust levels among and between the sites studied (Talley
et al.
2006b, p. 653).
The study also looked at the relationships between the presence or absence of valley elderberry longhorn beetle and distances from dirt and paved surfaces. The authors found that the presence of new and 1-year-old valley elderberry longhorn beetle exit holes was independent of both trail location and surface type (Talley
et al.
2006b, p. 654). Further, the study noted that valley elderberry longhorn beetle exit holes were found at all sites despite higher dust levels at some study sites, and concluded that levels of dust from dirt trails, paved trails, and access roads did not have a negative association with the presence of the species, despite the variability in condition of elderberry plants (Talley
et al.
2006b, pp. 654-655).
In another study, Talley and Holyoak (2009, entire) evaluated how the proximity to highways and highway construction activities affects the occupancy of the valley elderberry longhorn beetle and condition of elderberry shrubs. Field surveys from 2006 to 2008 were used to evaluate the effects of particulates, pollutants, and noise along portions of several highways in the northern Central Valley of California (Talley and Holyoak 2009, pp. 2-3). The study included a laboratory analysis of effects to elderberry leaves (i.e., dust levels, leaf area, carbon to nitrogen ratios, and exhaust elements) and an evaluation of statistical relationships between the distances from either a construction site or highway edge and both dust accumulation rates and elderberry characteristics (Talley and Holyoak 2009, p. 4). The study found no effect of the proximity of highways on dust accumulations and few effects related to potentially toxic elements in elderberry leaves (Talley and Holyoak 2009, p. 9). Noise levels were found to decrease with distance from highways; however, noise levels were similar at sites located immediately adjacent to highways, despite differences in traffic volume (Talley and Holyoak 2009, p. 6).
The researchers determined that the type of habitat and availability of elderberry shrubs were the primary factors influencing the likelihood of the presence of either recent or total (recent and old) valley elderberry longhorn beetle exit holes; no relationships were observed between distance from highways and distribution of exit holes (Talley and Holyoak 2009, p. 6). However, the
amount
of available elderberry habitat was found to be significantly lower along roadsides, and elderberry stem densities were smaller in sites immediately adjacent to highways when compared to riparian or control sites, or compared to remnant riparian and non-riparian scrub areas (Talley and Holyoak 2009, pp. 8-9). This was attributed to right-of-way management activities (e.g., mowing, pruning) rather than a direct stress effect of being located adjacent to highways (Talley and Holyoak 2009, p. 9).
These findings reinforce results of other studies in which a range of both elderberry quality and quantity characteristics have been found to influence the presence and abundance of the valley elderberry longhorn beetle (Talley and Holyoak 2009, p. 8; see
Habitat
discussion above in Background section). The authors of the highway study noted the need for additional larger scale studies as well as controlled experimental studies to test specific effects on valley elderberry longhorn beetle survival (e.g., an evaluation of whether roadside patches act as population sinks that attract individuals into areas that are not able to sustain populations (Pulliam 1988, pp. 658-660)) (Talley and Holyoak 2009, p. 11).
In summary, threats related to road and trail uses, and the effects of dust, do not represent significant impacts to the valley elderberry longhorn beetle. However, removal of elderberry shrubs along the roadways (for right-of-way management activities) is a more important factor and is discussed in more detail below (see discussion under
Pruning
).
Pruning
In our proposed rule, we briefly discussed pruning as part of a
Factor E
threat, termed Human Use (77 FR 60263; October 2, 2012). Because we consider pruning activities to be a potential threat related to destruction or modification of habitat, we discuss pruning as a separate
Factor A
threat and include results from a study that was not discussed in the proposed rule. Pruning or trimming of elderberry shrubs for highway or trail maintenance, or other purposes, is a common activity within the presumed extant occurrences of the valley elderberry longhorn beetle. Talley and Holyoak (2009, entire) conducted an experimental study to measure the effects of pruning of elderberry shrubs on the valley elderberry longhorn beetle and its host plant. Two experimental techniques (pruning and topping) were used within elderberry habitat found along portions
of the American River Parkway (Talley and Holyoak 2009, p. 29). The pruning experiment was designed to mimic the trimming (i.e., 50 percent of all branches 1 in (2.5 cm) or less in diameter) of elderberry shrubs that overhang roads and trails, while the topping experiment was designed to evaluate the removal of the top 3.28 ft (1 m) of a shrub or group of shrubs that often occurs beneath power lines and overhead obstructions (Talley and Holyoak 2009, p. 30). The experiments used measures of elderberry survival, growth, and condition as well as the presence and abundance of new valley elderberry longhorn beetle exit holes (Talley and Holyoak 2009, p. 30). The study found no “short-term” (2-4 weeks) changes in the survival, growth, or condition in response to the two experiments (Talley and Holyoak 2009, p. 32).
In addition, laboratory analyses to evaluate nutrient and defense chemical content indicated that neither experimental treatment had detectable effects on elderberry nutrition (Talley and Holyoak 2009, p. 32). The study also found that neither colonization nor loss of valley elderberry longhorn beetles from elderberry shrubs was affected by pruning or topping experiments; that is, the declines and increases in occupied shrubs was independent of trimming, and, if anything, was likely related to the initial presence of the species (Talley and Holyoak 2009, p. 31). The only negative effect reported from this experimental study was a temporary loss of habitat from the removal of stems, but these stems regrew, on average, within 3 to 4 years (Talley and Holyoak 2009, p. 33).
Based on the potential impacts from pruning described in the proposed rule, the pruning of elderberry shrubs, when conducted in accordance with the findings of experimental studies presented by Talley and Holyoak (2009, pp. 29-33), will likely have temporary impacts to the valley elderberry longhorn beetle. Additional experimental studies of the effects of pruning (e.g., at mitigation or restoration sites) would provide a more complete evaluation of the magnitude of this threat to the species.
Effects Related to Climate Change
In our proposed rule, we discussed the effects of climate change under
Factors A
and
E
(77 FR 60254-60255, 60262; October 2, 2012). We stated that we did not have information that would allow us to make meaningful predictions of the effects of changes in temperature and precipitation patterns relative to potential changes in elderberry habitat (77 FR 60255; October 2, 2012). We concluded in
Factor E
that climate change was not a significant factor affecting the persistence of the valley elderberry longhorn beetle (77 FR 60262; October 2, 2012).
In this withdrawal, we discuss threats related to the effects of climate change in
Factors A
and
E.
In
Factor A,
we provide a more robust discussion of both observed and predicted effects to hydrological patterns related to climate change effects for the Central Valley based on state-wide and regional probabilistic estimates of temperature and precipitation changes for California (using downscaled data from both global circulation models and nested regional climate models), and also present results of climate assessment tools to illustrate these predicted effects. In
Factor E,
we discuss the effects of climate change related to the survivorship and reproductive success of the valley elderberry longhorn beetle.
Our analyses under the Act include consideration of observed or likely environmental changes resulting from ongoing and projected changes in climate. As defined by the Intergovernmental Panel on Climate Change (IPCC), the term “climate” refers to the mean and variability of different types of weather conditions over time, with 30 years being a typical period for such measurements, although shorter or longer periods also may be used (IPCC 2013a, p. 1450). The term “climate change” thus refers to a change in the mean or the variability of relevant properties, which persists for an extended period, typically decades or longer, due to natural conditions (e.g., solar cycles) or human-caused changes in the composition of atmosphere or in land use (IPCC 2013a, p. 1450).
Scientific measurements spanning several decades demonstrate that changes in climate are occurring. In particular, warming of the climate system is unequivocal and many of the observed changes in the last 60 years are unprecedented over decades to millennia (IPCC 2013b, p. 4). The current rate of climate change may be as fast as any extended warming period over the past 65 million years and is projected to accelerate in the next 30 to 80 years (National Research Council 2013, p. 5). Thus, rapid climate change is adding to other sources of extinction pressures, such as land use and invasive species, which will likely place extinction rates in this era among just a handful of the severe biodiversity crises observed in Earth's geological record (American Association for the Advancement of Sciences (AAAS) 2014, p. 17).
Examples of various other observed and projected changes in climate and associated effects and risks, and the bases for them, are provided for global and regional scales in recent reports issued by the IPCC (2013c, 2014), and similar types of information for the United States and regions within it can be found in the National Climate Assessment (Melillo
et al.
2014, entire).
Results of scientific analyses presented by the IPCC show that most of the observed increase in global average temperature since the mid-20th century cannot be explained by natural variability in climate and is “extremely likely” (defined by the IPCC as 95 to 100 percent likelihood) due to the observed increase in greenhouse gas (GHG) concentrations in the atmosphere as a result of human activities, particularly carbon dioxide emissions from fossil fuel use (IPCC 2013b, p. 17 and related citations).
Scientists use a variety of climate models, which include consideration of natural processes and variability, as well as various scenarios of potential levels and timing of GHG emissions, to evaluate the causes of changes already observed and to project future changes in temperature and other climate conditions. Model results yield very similar projections of average global warming until about 2030, and thereafter the magnitude and rate of warming vary through the end of the Century depending on the assumptions about population levels, emissions of GHGs, and other factors that influence climate change. Thus, absent extremely rapid stabilization of GHGs at a global level, there is strong scientific support for projections that warming will continue through the 21st century, and that the magnitude and rate of change will be influenced substantially by human actions regarding GHG emissions (IPCC 2013b, 2014; entire).
Global climate projections are informative, and, in some cases, the only or the best scientific information available for us to use. However, projected changes in climate and related impacts can vary substantially across and within different regions of the world (e.g., IPCC 2013c, 2014; entire) and within the United States (Melillo
et al.
2014; entire). Therefore, we use “downscaled” projections when they are available and have been developed through appropriate scientific procedures, because such projections provide higher resolution information that is more relevant to spatial scales used for analyses of a given species (see Glick
et al.
2011, pp. 58-61, for a discussion of downscaling).
Various changes in climate may have direct or indirect effects on species. These may be positive, neutral, or negative, and they may change over time, depending on the species and other relevant considerations, such as interactions of climate with other variables such as habitat fragmentation (for examples, see Franco
et al.
2006; Forister
et al.
2010; Galbraith
et al.
2010; Chen
et al.
2011; Bertelsmeier
et al.
2013, entire). In addition to considering individual species, scientists are evaluating potential climate change-related impacts to, and responses of, ecological systems, habitat conditions, and groups of species (e.g., Deutsch
et al.
2008; Berg
et al.
2010; Euskirchen
et al.
2009; McKechnie and Wolf 2010; Sinervo
et al.
2010; Beaumont
et al.
2011; McKelvey
et al.
2011; Rogers and Schindler 2011; Bellard
et al.
2012).
As an example, Hickling
et al.
(2006, entire) analyzed the changes in distributions of groups of vertebrates and invertebrates, including longhorn beetles, in Great Britain to determine whether range shifts (both in latitude and elevation) have occurred over an approximately 25-year time span. For 11 species of longhorn beetles, the study found that, for grid squares (6.2 mi (10 km)) considered to be well-recorded (i.e., those that had at least 10 percent of that group recorded present in both study time periods), there was an average shift northward of 27 mi (43 km) and an average elevational shift of 86 ft (26 m) from 1960-1970 to 1985-1995 (Hickling
et al.
2006, pp. 451-453). The authors stressed the importance of recognizing that observed distribution shifts due to climate change are occurring concurrently with changes in land use and other environmental factors (Hickling
et al.
2006, p. 454).
Effects from climate change in California, with its watersheds dominated by snowmelt hydrology, are expected to have important impacts to hydrological processes that will cascade into human and ecological systems at many scales (Kiparsky
et al.
2014, p. 1). Likely effects include a reduction in snowpack and stream flow as well as changes in stream flow patterns, all of which present significant challenges in a State in which water, energy, agricultural, and ecological systems are linked together (Barnett
et al.
2008, p. 1082). These effects have recently been summarized by hydrologic region in the California Department of Water Resources Public Review Draft of the
California Water Plan
(CWP)
Update 2013
(CDWR 2013). The CWP describes future actions that are intended to move California toward a more sustainable management of water resources and more resilient water management systems, and identifies objectives to support environmental stewardship (CDWR 2013, p. ES-1). Two hydrologic regions—the Sacramento River and the San Joaquin River—defined in the CWP encompass nearly all of our presumed extant occurrences (Figure 2) of the valley elderberry longhorn beetle (Fresno County not included). A summary of climate change effects projected for these two regions is described in the paragraphs below.
Regional temperature observations for assessing climate change are often used as an indicator of how climate is changing, and the Western Regional Climate Center (WRCC) has defined 11 climate regions for evaluating various climate trends in California (Abatzoglou
et al.
2009, p. 1535). These climate regions have different boundaries for California than the CWP hydrologic regions, but are considered to be more representative of California's diverse climatic regimes than standard climate divisions (Pierce
et al.
2013, p. 843). The relevant WRCC climate regions for the distribution of the valley elderberry longhorn beetle are the Sacramento-Delta and the San Joaquin Valley regions.
Two indicators of temperature, the increase in mean temperature and the increase in maximum temperature, are important for evaluating trends in climate change in California. For the Sacramento-Delta climate region, linear trends (evaluated over a 100-year time period) indicate an increase in mean temperatures (Jan-Dec) of approximately 1.96 °F (1.09 °C) since 1895, and 3.0 °F (1.67 °C) since 1949 (WRCC 2014a). For the San Joaquin Valley climate region, the 100-year trend in mean temperature (Jan-Dec) indicates an increase of approximately 1.4 °F (0.78 °C) since 1895, and 2.62 °F (1.45 °C) since 1949 (WRCC 2014c). Similarly, the maximum temperature 100-year trend for the Sacramento-Delta region shows an increase of about 1.42 °F (0.8 °C) since 1895, and 1.92 °F (1.07 °C) since 1949 (WRCC 2014b). The maximum temperature 100-year trend for the San Joaquin Valley climate region shows an increase of about 0.38 °F (0.21 °C) since 1895, and 1.09 °F (0.60 °C) since 1949 (WRCC 2014d). It is logical to assume the rate of temperature increase for both regions is higher for the second time period (since 1949) than for the first time period (since 1895) due to the increased use of fossil fuels in the 20th century.
Although these observed trends provide information relative to how climate has changed in the past, climate science models are used to simulate and develop future climate projections (CDWR 2013, p. SR-76). Pierce
et al.
(2013, entire) presented both state-wide and regional probabilistic estimates of temperature and precipitation changes for California (by the 2060s) using downscaled data from 16 global circulation models and 3 nested regional climate models. The study looked at a historical (1985-1994) and a future (2060-2069) time period using the IPCC Special Report on Emission Scenarios A2 (Pierce
et al.
2013, p. 841), which is an IPCC-defined scenario used for the IPCC's Third and Fourth Assessment reports, and is based on a global population growth scenario and economic conditions that result in a relatively high level of atmospheric GHGs by 2100 (IPCC 2000, pp. 4-5; see Stocker
et al.
2013, pp. 60-68, and Walsh
et al.
2014, pp. 25-28, for discussions and comparisons of the prior and current IPCC approaches and outcomes). Importantly, the projections included daily distributions and natural internal climate variability (Pierce
et al.
2013, pp. 852-853).
Simulations using these downscaling methods project an increase in yearly temperature for the Sacramento-Delta climate region ranging from 1.9 °C (3.42 °F) to 2.8 °C (5.04 °F) by the 2060s time period (Pierce
et al.
2013, p. 844), compared to 1985-1994. For the San Joaquin Valley climate region, the simulations show an increase in average yearly temperature ranging from 3.6 °F (2.0 °C) to 5.04 °F (2.8 °C) by the 2060s (Pierce
et al.
2013, p. 844). The simulations indicated an upper temperature increase of 4.14 °F (2.3 °C) from 1985-1994 to 2060-2069 (averaged across models) for both the Sacramento-Delta and San Joaquin Valley regions (Pierce
et al.
2013, p. 842).
We also reviewed projections from Cal-Adapt, a web-based, climate adaptation planning tool that synthesizes existing downscaled climate change scenarios and climate impact research, and presents the predictions in an interactive, graphical layout (California Energy Commission 2011). Projections of changes in annual averages in temperature for the Central Valley using the Cal-Adapt Climate tool indicate an increase in temperature ranging from about 3.4-3.8 °F (2.0-2.1 °C) under the IPCC low emissions scenario (B1), to an increase in temperature ranging from 6.0-6.6 °F (3.4-3.7 °C) under the IPCC higher emissions scenario (A2) (Cal-Adapt 2014a). Both of these scenarios represent comparisons between the baseline period (1961-1990) and the end-of-century period (2070-2090). The
Cal-Adapt projection of an increase of about 2.0 °C (3.4 °F) in annual average temperature is very similar to the lower end of the range of yearly temperature simulations presented by Pierce
et al.
(2013, entire) for both regions with the A2 emissions scenario.
Precipitation patterns for California are quite variable year to year. Based on paleoclimatic data (e.g., tree-ring reconstructions of streamflow and precipitation), hydrologic conditions in California (and the west) are naturally widely varying, and include a pattern of recurring and extended droughts (CDWR 2008, p. 3). However, the 100-year trends for the Sacramento-Delta and San Joaquin Valley regions indicate a large change in the rate of increase (or, in some cases, a decrease) in precipitation over the winter months (December-February), which is generally when the Central Valley receives the bulk of its rainfall for the year. For the Sacramento-Delta region, rainfall data from WRCC show a 100-year linear trend in winter of an increase in precipitation of 2.26 in (5.74 cm) from 1895 to present (February 2014), but an increase of only 0.53 in (1.35 cm) from 1975 to present (WRCC 2014e). Similar precipitation patterns are found in the San Joaquin Valley region; that is, in winter months, there is an increase in precipitation of 0.52 in (1.35 cm) for the 100-year trend beginning in 1895 to present, but a 1.05 in (2.67 cm) decrease for the 100-year trend beginning in 1975 to present (WRCC 2014f). The 100-year trends beginning in 1975 and ending at present (February 2014) for both regions show great variability, which is likely due, in part, to the shorter time period being evaluated. However, observed changes in hydrologic patterns (i.e., low-frequency changes in the hydrological cycle such as river flow, temperature, and snowpack) over the western United States from 1950 to 1999 have been found to be partially attributed to the effects of climate change (Barnett
et al.
2008, p. 1080).
Downscaled probabilistic climate models were also used by Pierce
et al.
(2013, pp. 848-852) to evaluate changes in precipitation patterns for California resulting from the effects of climate change. Annual averages show different patterns in precipitation changes than those by season; that is, model results indicate increases in winter (December-February) precipitation for the Sacramento-Delta and San Joaquin Valley climate regions of 5 percent and 1 percent, respectively (averaged across all models, comparing the mean over the 1985-1994 time period to the mean over 2060-2069) (Pierce
et al.
2013, p. 849). However, these wetter conditions in winter are largely offset by drier conditions predicted for the remainder of the year (e.g., 4 to 20 percent decrease in precipitation for the Sacramento-Delta region) (Pierce
et al.
2013, p. 849). Model results for the yearly change in precipitation indicate a 3 percent decrease in precipitation for the Sacramento-Delta, and a 6 percent decrease for the San Joaquin Valley region (averaged across all models, using mean changes over the 1985-1994 time period compared to 2060-2069) (Pierce
et al.
2013, pp. 848-849).
Changing precipitation patterns and resultant changes in hydrologic conditions are already being observed for California. In the last century, the average early spring snowpack in the Sierra Nevada decreased by about 10 percent, which represents a loss of 1.5 million acre-feet of snowpack storage (CDWR 2008, p. 3). We reviewed Cal-Adapt projections for snowpack for the western Sierra Nevada region of California, which supplies water to many of the river systems within the eastern portion of the Central Valley. Projected changes in April snow water equivalence across the western Sierra Nevada region (eastern edge of the Central Valley) indicate about an 80 percent reduction in snow moisture under a low emissions scenario (B1); and about a 90 percent reduction in snow moisture under a high emissions scenario (A2), between a baseline time period (1961 to 1990) and an end-of-century period (2070 to 2090) (Cal-Adapt 2014b).
A downscaled simulation of the potential impacts of climate warming on hydrology and water supply operations was developed expressly for the Tuolumne and Merced River basins in California (Kiparsky
et al.
2014, entire), which includes the southeastern portion of the valley elderberry longhorn beetle's current range. Although the simulation model (based on a Water Evaluation and Planning model) was developed primarily to evaluate water supply concerns for urban, agricultural, and environmental uses, the results are important as they relate to predicted effects to streamflow and timing of hydrological events in this portion of the Central Valley. In response to climate warming scenarios (2 °C, 4 °C, and 6 °C increases), the simulation indicated a shift in timing and magnitude of seasonal flows for these two basins; that is, earlier snowmelt and a subsequent 3-month earlier shift in the water year for peak flows (Kiparsky
et al.
2014, p. 10).
Finally, Huang
et al.
(2012, entire) conducted a hydrologic and sensitivity analysis specifically for a portion of the Sacramento River climate region, the Upper Feather River watershed, which represents another snow-dominated watershed in California. Using six global climate models (GCMs) with two IPCC emissions scenarios (A2 and B1), the results of a model based on a Precipitation-Runoff Modeling System indicate significant changes in streamflow timing and increases in both frequency and magnitude of extreme flows (Huang
et al.
2012, p. 138). Although the authors stress the uncertainty in the model results, the simulation found, for example, that with a 4 °C (7.2 °F) warming, there was an 11 percent increase in the 100-year annual maximum daily flow and a 35 percent decrease in the 10-year minimum 7-day flow (i.e., drought condition) (Huang
et al.
2012, p. 147). The increase in annual peak flow was attributed to the combined effect of more rainfall and less snowmelt with climate warming during winter months (January-March) (Huang
et al.
2012, p. 147).
As described above, the survival and reproduction of the valley elderberry longhorn beetle, is dependent on two elderberry taxa, which in turn are dependent upon ecological processes supported by climatic conditions (precipitation and temperature) and other environmental factors (e.g., elevation). Effects from climate change on the riparian ecosystems upon which the valley elderberry longhorn beetle depends are expected to include an increase in the intensity of both wet and dry periods due to changes in hydrologic conditions within those California watersheds driven by snowmelt, which is likely to alter streamflow patterns for the riverine systems that occupy the Sacramento-Delta and San Joaquin Valley regions (CDWR 2013, pp. SJR-73-SJR-75, SR-76-SR-78 and references cited therein). Altered flow regimes (both volume and timing) will influence the mechanisms that support riparian plant communities, including elderberry habitat. Shifts in location and species composition of riparian vegetation can occur due to changes in groundwater and surface water levels (Kløve
et al.
2013, p. 3).
The effects of climate change are also expected to result in increased temperatures for the Central Valley, and, when combined with current trends and future changes in hydrologic patterns (e.g., timing of snowmelt and peak flows), will result in an increase in the frequency and duration of drought conditions in California. Hanson
et al.
(2012, entire) presented a supply and demand modeling framework to
simulate and analyze potential climate change effects on conjunctive uses of water resources within California's Central Valley from 2000-2100. This simulation and analysis (linking downscaled GCM simulation results, the A2 or rapidly increasing GHG emissions scenario, with regional hydrologic models) includes the demands, uses, and movements of water for irrigation and natural vegetation, runoff from local mountains, and the responses of supply from groundwater and streamflow (Hanson
et al.
2012, p. 3).
Results from the simulation include intermittent climatic droughts from 2000-2050 and sustained droughts in 2050-2100 due to reduced precipitation (Hanson
et al.
2012, p. 11). The drought events were found to have significant effects on surface water and groundwater deliveries and are likely to produce secondary effects, including a reduction in water for riparian vegetation and surface water deliveries (Hanson
et al.
2012, pp. 11, 19). The simulated changes also produce large declines in flows draining into the Central Valley from the surrounding mountain watersheds, with a decline of over 45 percent of potential total basin discharge by 2100 (Hanson
et al.
2012, p. 11). Reductions in streamflow diversions in this scenario are, therefore, expected for riparian vegetation and irrigation uses, including the Tuolumne River, the San Joaquin Basin, and Bear River in the Sacramento Valley Tulare Basin (Hanson
et al.
2012, p. 12). Additionally, the reduction in surface water diversions increases the demand for groundwater pumping, negatively affecting groundwater levels (Hanson
et al.
2012, p. 12) and further reducing water levels within riparian systems, and likely causing significant land subsidence along the southeastern San Joaquin and Sacramento Valleys (Hanson
et al.
2012, p. 20).
Other predictions of riparian vegetation changes related to climate-driven hydrological changes have found reductions in species-rich riparian forests (boreal river system in northern Sweden) (Ström
et al.
2012, pp. 54-56) or shifts in successional phases of riparian vegetation (Mediterranean rivers) (Rivaes
et al.
2013, entire).
Predicted effects on both surface and groundwater availability are likely to negatively affect the regeneration and sustainability of riparian vegetation, including elderberry shrubs, though we are unaware of any comprehensive evaluation of specific responses of this host plant. The predicted changes in hydrologic conditions are also likely to favor the spread of invasive plants.
In summary, the best available data indicate that climate change effects will add to the destruction and modification of habitat for the valley elderberry longhorn beetle both currently and in the future. Although, we are unable to assess in specific quantitative terms the magnitude of the impact due to the uncertainty relative to climate change effects that will occur and the degree to which hydrology and water diversions will be affected, the best available data indicate long-term climate change effects will continue to have an overall negative effect on the available habitat throughout the range of the valley elderberry longhorn beetle.
Invasive Plants
Competition for resources between elderberry plants and invasive plants and effects to elderberry habitat from invasive plants were not included as potential threats in our 2006 5-year review (Service 2006a, entire) or in our proposed rule, though we concluded in the proposed rule that these threats were not well-studied and had not been identified as widespread threats to the species or its habitat (77 FR 60250, October 2, 2012). However, the natural plant communities of the Central Valley have been altered by removal of native trees, as described above, and by the rapid spread of invasive plants following the influx of immigrants and livestock into the area during the gold rush era (Mack 1989, p. 165). As an example, the replacement of native plants, particularly within grassland communities, by nonnative annual grasses was nearly complete by 1880 (Mack 1989, p. 166). Based on comments received from peer reviewers and additional information not assessed in the proposed rule, we include here an updated and more detailed discussion of effects to the valley elderberry longhorn beetle from invasive plants to better assess this potential threat.
The Central Valley, as with other parts of California, continues to experience new invasions (e.g., California Invasive Plant Council Symposium 2003, entire). The California Invasive Plant Council (Cal-IPC) has developed an interactive Web site (CalWeedMapper 2014) that illustrates invasive plant distributions based on occurrence data and suitable range modeling using climate data. CalWeedMapper was designed as a strategic tool to identify management opportunities for control and eradication of invasive plants. County and regional species maps and associated reports can be created for individual invasive species that describe their abundance, trends, and spatial distribution. Although the information may contain errors (i.e., misidentifications or imprecise location information), the maps provide useful information on current distributions and trends of invasive plants in California.
Talley (2005, p. 18) observed a short-term positive effect to the valley elderberry longhorn beetle from the invasive black locust (
Robinia pseudoacacia
) (a nitrogen-fixing tree); however, this plant has the potential to displace native plants in riparian communities (Hunter 2000, p. 275), which can negatively affect the long-term survival of elderberry plants (Talley 2005, p. 33). Using CalWeedMapper, we were able to create a regional (Central Valley) report and map for black locust (Cal-IPC 2014b). Within the presumed extant occurrences of the valley elderberry longhorn beetle, there is a spreading trend for this invasive plant in Butte County (Cal-IPC 2014b). This invasive plant is also considered to be “medium” in abundance in parts of Sacramento County and is “low” in several other areas within the northern portion of the Central Valley where the valley elderberry longhorn beetle has been observed (Cal-IPC 2014a). Black locust is also illustrated as “spreading” in several areas of California outside of the Central Valley (Cal-IPC 2014b).
The spread of invasive plant species is expected to become more severe in association with future changes in climate, such as drought (e.g., Bradley
et al.
2010, entire). For example, the black locust is described as being drought tolerant, and as propagating easily from seeds and having seeds that spread easily (Benesperi
et al.
2012, p. 3556; see also Temperate Climate Permaculture 2014). In studies elsewhere, forest plant diversity has been shown to decrease in areas where the black locust has spread Benesperi
et al.
2012, pp. 3560-3561), and a recent experimental study concluded that its nitrogen-fixing ability appears to give this species a competitive advantage under drought conditions (Wurzburger and Miniat 2013, pp. 1120-1125). A commercial horticulture Web site describes black locust as a species that is suitable for use in times of climate change due to its adaptability to heat and water stress (SilvaSelect 2014). As noted above, the CalWeedMapper provides maps with general information on current distributions and trends of invasive plants in California; the maps do not, however, include projections of future distribution in relation to climate change projections. Based on the available scientific information about the black locust, we expect that its range
will continue to expand in response to increased temperatures and drought projected for the range of the valley elderberry longhorn beetle (see above for climate change projections).
Black walnut (
Juglans hindsii
), an invasive plant found on riparian floodplains along the Sacramento River, is strongly associated with elderberry and may also be invading formerly open elderberry habitat (Vaghti
et al.
2009, pp. 33-35). Black walnut is also considered a nonnative woody plant in the Sacramento Valley, having become established in riparian zones since its introduction into the valley in the latter 19th and early 20th centuries as an ornamental plant or as root stock for English walnut (
Juglans regia
) (Hunter
et al.
2003, p. 41). As such, black walnut has been described as the most widespread nonnative in the Sacramento Valley, based on 47 plots surveyed along 16 streams in the valley and adjacent foothills in 2003 (Hunter
et al.
2003, pp. 39-46), including many areas where the valley elderberry longhorn beetle has been observed (e.g., Feather River, American River, Butte Creek, Big Chico Creek).
Chinese tallowtree (
Triadica sebifera,
formerly
Sapium sebiferum
) is a deciduous tree native to east Asia that has become a major invasive species in the southeastern United States and, since its introduction as a shade tree in urban areas of California, has now begun to spread in riparian areas of California (Cal-IPC 2014c). This invasive plant has been difficult to eradicate once established (Bower
et al.
2009, p. 393). Bower
et al.
(2009, entire) evaluated the invasion potential of Chinese tallowtree in California's Central Valley. This study found that this invasive species can colonize areas that are immediately adjacent to water sources; though drought-intolerant seedlings appear to restrict colonization in drier (higher elevation) areas (Bower
et al.
2009, pp. 387, 393). CalWeedMapper illustrates a spreading trend of Chinese tallowtree for areas within Butte, Yuba, Sutter, and Sacramento Counties (Cal-IPC 2014c). Bower
et al.
(2009, p. 387) reported naturalizing populations of this invasive species along the Sacramento, San Joaquin, and American Rivers.
Hunter
et al.
(2003, pp. 42, 45) also described a patchy distribution of a large number of other woody nonnative plants (i.e., not including black walnut) in these riparian zones, but with relatively low abundance (less than 1 to 15 percent mean cover). However, the study indicated that some species (e.g., tree-of-heaven (
Ailanthus altissima
), Chinese tallowtree, scarlet wisteria (
Sesbania punicea
), tamarisk (
Tamarix
sp.)) are likely expanding their ranges and increasing in abundance in the Central Valley (Hunter
et al.
2003, p. 42). In addition, this study also noted that the nonnative Himalayan blackberry (
Rubus discolor
) was the typical dominant plant in the well-developed shrub layer of the riparian zones surveyed (34 percent mean cover, where present; observed in 70 percent of the plots surveyed) (Hunter
et al.
2003, p. 42). Finally, Golet
et al.
(2013, pp. 14, 17) found that the areal extent of several nonnative, invasive plants had increased in riparian zones along one section of the Sacramento River (Red Bluff to Colusa) from 1999 to 2007, including an increase in black walnut within restoration and remnant riparian sites.
Vegetation type conversion or other shifts in native plant communities due to invasive plants represents environmental changes that are likely to have a negative effect on the metapopulation dynamics of the valley elderberry longhorn beetle. Although there are reported trends of expansions of invasive and nonnative plants (e.g., black locust, black walnut) within the presumed extant occurrences of the valley elderberry longhorn beetle, we are not aware of comprehensive studies evaluating their range-wide effects on occupied or suitable habitat of the valley elderberry longhorn beetle.
In summary, at this time, the best available scientific and c
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