Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for Mount Charleston Blue Butterfly (Plebejus shasta charlestonensis)
Federal Register, Volume 79 Issue 135 (Tuesday, July 15, 2014)
Federal Register Volume 79, Number 135 (Tuesday, July 15, 2014)
Proposed Rules
Pages 41225-41245
From the Federal Register Online via the Government Printing Office www.gpo.gov
FR Doc No: 2014-16355
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
Docket No. FWS-R8-ES-2013-0105; 4500030114
RIN 1018-AZ91
Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for Mount Charleston Blue Butterfly (Plebejus shasta charlestonensis)
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Proposed rule.
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SUMMARY: We, the U.S. Fish and Wildlife Service, propose to designate critical habitat for the Mount Charleston blue butterfly (Plebejus shasta charlestonensis) under the Endangered Species Act. In total, approximately 5,561 acres (2,250 hectares) are being proposed for designation as critical habitat. The proposed critical habitat is located in the Spring Mountains of Clark County, Nevada. If we finalize this rule as proposed, it would extend the Act's protections to this species' critical habitat. We also announce the availability of a draft economic analysis of the proposed designation of critical habitat for the Mount Charleston blue butterfly.
DATES: We will accept comments on the proposed rule or draft economic analysis that are received or postmarked on or before September 15, 2014. Comments submitted electronically using the Federal eRulemaking Portal (see ADDRESSES) must be received by 11:59 p.m. Eastern Time on the closing date.
We must receive requests for public hearings, in writing, at the address shown in FOR FURTHER INFORMATION CONTACT by August 29, 2014.
Public Meeting: We will hold a public meeting on this proposed rule on August 19, 2014, from 6 to 8 p.m. at the location specified in ADDRESSES. People needing reasonable accommodations in order to attend and participate in the public meeting should contact Dan Balduini, Nevada Fish and Wildlife Office, as soon as possible (see FOR FURTHER INFORMATION CONTACT).
ADDRESSES: You may submit comments on the proposed rule or draft economic analysis by one of the following methods:
(1) Electronically: Go to the Federal eRulemaking Portal: http://www.regulations.gov. In the Search box, enter FWS-R8-ES-2013-0105, which is the docket number for this rulemaking. You may submit a comment by clicking on ``Comment Now!''
(2) By hard copy: Submit by U.S. mail or hand-delivery to: Public Comments Processing, Attn: FWS-R8-ES-2013-0105; Division of Policy and Directives Management; U.S. Fish and Wildlife Service; 4401 N. Fairfax Drive, MS 2042-PDM; Arlington, VA 22203.
We request that you send comments only by the methods described above. We will post all comments on http://www.regulations.gov. This generally means that we will post any personal information you provide us (see the Public Comments section below for more information).
Document availability: The draft economic analysis is available at http://www.fws.gov/Nevada, at http://www.regulations.gov at Docket No. FWS-R8-ES-2013-0105, and at the Nevada Fish and Wildlife Office (see FOR FURTHER INFORMATION CONTACT). The coordinates or plot points or both from which the map in the rule portion is generated, as well as any additional tools or supporting information that we may develop for this critical habitat designation, will also be available from these sources and included in the administrative record for this critical habitat designation.
Public meeting: The public meeting regarding the proposed critical habitat designation for the Mount Charleston blue butterfly will be held at the U.S. Fish and Wildlife Service office building, 4701 N. Torrey Pines Drive, Las Vegas, Nevada.
FOR FURTHER INFORMATION CONTACT: Edward D. Koch, Field Supervisor, U.S. Fish and Wildlife Service, Nevada Fish and Wildlife Office, 1340 Financial Blvd., Suite 234, Reno, Nevada 89502-7147; telephone (775) 861-6300 or facsimile (775) 861-5231. If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 800-877-8339.
SUPPLEMENTARY INFORMATION:
Executive Summary
Why we need to publish a rule. This is a proposed rule to designate critical habitat for the endangered Mount Charleston blue butterfly (Plebejus shasta charlestonensis). Under the Act, critical habitat shall be designated, to the maximum extent prudent and determinable, for any species determined to be an endangered or threatened species under the Act. Designations and revisions of critical habitat can be completed only by issuing a rule. In total, we are proposing approximately 5,561 acres (2,250 hectares) for designation as critical habitat for the Mount Charleston blue butterfly in the Spring Mountains of Clark County, Nevada. This proposal fulfills obligations to submit a proposed critical habitat rule or finalize a not prudent determination for critical habitat for the Mount Charleston blue butterfly to the Federal Register in accordance with In re: Endangered Species Act Section 4 Deadline Litig., Misc. Action No. 10-377 (EGS), MDL Docket No. 2165 (D.D.C.).
The basis for our action. Section 4(b)(2) of the Endangered Species Act states that the Secretary shall designate and make revisions to critical habitat on the basis of the best available scientific data after taking into consideration the economic impact, national security impact, and any other relevant impact of specifying any particular area as critical habitat. The Secretary may exclude an area from critical habitat if she determines that the benefits of such exclusion outweigh the benefits of specifying such area as part of the critical habitat, unless she determines, based on the best scientific data available, that the failure to designate such area as critical habitat will result in the extinction of the species.
We prepared an economic analysis of the proposed designation of critical habitat. In order to consider the economic impacts of the proposed critical habitat designation, we prepared an analysis of the economic impacts of the proposed critical habitat designation and related factors. We are announcing the availability of the draft economic analysis, and seek public review and comment.
We will seek peer review. We are seeking comments from knowledgeable individuals with scientific expertise to review our analysis of the best available science and application of that science and to provide any additional scientific information to improve this proposed rule. We have invited peer reviewers to comment on our specific assumptions and conclusions in this critical habitat designation. Because we will consider all comments and information received during the comment period, our final determinations may differ from this proposal.
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Information Requested
We intend that any final action resulting from this proposed rule will be based on the best scientific and commercial data available and be as accurate and as effective as possible. Therefore, we request comments or information from other concerned government agencies, the scientific community, industry, or any other interested party concerning this proposed rule. We particularly seek comments concerning:
(1) The reasons why we should or should not designate habitat as ``critical habitat'' under section 4 of the Act (16 U.S.C. 1531 et seq.) including whether there are threats to the species from human activity, the degree of which can be expected to increase due to the designation, and whether that increase in threat outweighs the benefit of designation such that the designation of critical habitat may not be prudent.
(2) Specific information on:
(a) The amount and distribution of Mount Charleston blue butterfly habitat;
(b) What areas, that were occupied at the time of listing (or are currently occupied) and that contain features essential to the conservation of the species, should be included in the designation and why;
(c) Special management considerations or protection that may be needed in critical habitat areas we are proposing, including managing for the potential effects of climate change;
(d) What areas not occupied at the time of listing are essential for the conservation of the species and why; and
(e) The larval host or adult nectar plants: Astragalus calycosus var. calycosus (Torrey's milkvetch), Oxytropis oreophila var. oreophila (mountain oxytrope), Astragalus platytropis (Broad keeled milkvetch) and Erigeron clokeyi (Clokey's fleabane), Hymenoxys lemmonii (Lemmon bitterweed), Hymenoxys cooperi (Cooper rubberweed), and Eriogonum umbellatum var. versicolor (sulphur-flower buckwheat).
(f) Potential effects from the Carpenter 1 Fire that occurred in July 2013 to populations and distribution of the Mount Charleston blue butterfly, and changes to the amount and distribution of habitat for the Mount Charleston blue butterfly that may have been altered by the fire, including information on the ability of the Mount Charleston blue butterfly or its habitat to recover from the effects of the Carpenter 1 Fire.
(3) Land use designations and current or planned activities in the subject areas and their possible impacts on proposed critical habitat.
(4) Whether we should remove some areas from the final designation of critical habitat due to high levels of recreational use that may have significantly diminished the presence or quality of the physical and biological features of this habitat, as discussed below in Areas Surrounding Recreation Infrastructure in the Proposed Critical Habitat Designation section. These locations are within the established boundaries or developed infrastructure (for example, roads, parking areas, fire pits, etc.) of campgrounds and day use areas that have extremely high levels of public visitation and associated recreational disturbance. We are specifically seeking public comment on whether the locations, identified in Areas Surrounding Recreation Infrastructure below, contain the physical or biological features essential to the conservation of the species to inform our determination of whether they meet the definition of critical habitat. A map of the specific locations for potential removal can be found on the Nevada Fish and Wildlife Office Web site at: http://www.fws.gov/nevada/ and at http://www.regulations.gov at Docket No. FWS-R8-ES-2013-0105.
(5) Information on the projected and reasonably likely impacts of climate change on the Mount Charleston blue butterfly and proposed critical habitat.
(6) Any probable economic, national security, or other relevant impacts of designating any area that may be included in the final designation, and the benefits of including or excluding areas that exhibit these impacts.
(7) Information on the extent to which the description of economic impacts in the draft economic analysis is a reasonable estimate of the likely economic impacts.
(8) The likelihood of adverse social reactions to the designation of critical habitat, as discussed in the associated documents of the draft economic analysis, and how the consequences of such reactions, if likely to occur, would relate to the conservation and regulatory benefits of the proposed critical habitat designation.
(9) Whether any specific areas we are proposing for critical habitat designation should be considered for exclusion under section 4(b)(2) of the Act, and whether the benefits of potentially excluding any specific area outweigh the benefits of including that area under section 4(b)(2) of the Act.
(10) Whether we could improve or modify our approach to designating critical habitat in any way to provide for greater public participation and understanding, or to better accommodate public concerns and comments.
You may submit your comments and materials concerning this proposed rule by one of the methods listed in ADDRESSES. We request that you send comments only by the methods described in ADDRESSES.
All comments submitted electronically via http://www.regulations.gov will be presented on the Web site in their entirety as submitted. For comments submitted via hard copy, we will post your entire comment--including your personal identifying information--on http://www.regulations.gov. You may request at the top of your document that we withhold personal information such as your street address, phone number, or email address from public review; however, we cannot guarantee that we will be able to do so.
Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on http://www.regulations.gov, or by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, Nevada Fish and Wildlife Office (see FOR FURTHER INFORMATION CONTACT).
Previous Federal Actions
In an earlier Federal Register volume, we published a final rule to list the Mount Charleston blue butterfly as endangered (78 FR 57750, September 19, 2013). This proposed critical habitat designation is based upon determinations made in the final listing rule. For additional information on previous Federal actions, please refer to the September 19, 2013, final listing rule.
On September 27, 2012, we published a proposed rule (77 FR 59518) to list the Mount Charleston blue butterfly as endangered, and the lupine blue butterfly, Reakirt's blue butterfly, Spring Mountains icarioides blue butterfly, and two Spring Mountains dark blue butterflies as threatened due to similarity of appearance to the Mount Charleston blue butterfly. A 60-day comment period following publication of this proposed rule closed on November 13, 2012. Based on comments we received during this period, we determined that designation of critical habitat for the Mount Charleston blue butterfly is prudent. This document consists of a proposed rule to designate critical habitat for the Mount Charleston blue butterfly.
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Background
It is our intent to discuss below only those topics directly relevant to the designation of critical habitat for the Mount Charleston blue butterfly in this proposed rule. For further information on the subspecies' biology and habitat, population abundance and trends, distribution, demographic features, habitat use and conditions, threats, and conservation measures, please see the final listing rule for Mount Charleston blue butterfly, published September 19, 2013 (78 FR 57750); the September 27, 2012, proposed rule (77 FR 59518); and the 12-month finding for the species (76 FR 12667; March 8, 2011). These documents are available from the Environmental Conservation Online System (ECOS) (http://ecos.fws.gov/ecos/indexPublic.do), the Nevada Fish and Wildlife Office Web site (http://www.fws.gov/nevada/), or from the Federal eRulemaking Portal (http://www.regulations.gov).
Prudency Determination
In our proposed listing rule for the Mount Charleston blue butterfly (76 FR 59518; September 27, 2012), we concluded that designation of critical habitat was not prudent in accordance with 50 CFR 424.12(a)(1), because collection was a threat to the Mount Charleston blue butterfly, and designation was expected to increase the degree of this threat to the subspecies and its habitat. In that proposal, we requested information from the public during the public comment period and solicited information from peer reviewers on whether the determination of critical habitat was prudent and determinable, what physical or biological features were essential to the conservation of the subspecies, and what areas contained those features or were otherwise essential for the conservation of the species.
In the final listing rule, we reported that peer reviewers commented that designating critical habitat would not increase the threat to the Mount Charleston blue butterfly from collection, because those individuals interested in collecting Mount Charleston blue butterflies would be able to obtain occurrence locations from other sources, such as the internet. In addition, the U.S. Department of Agriculture's Forest Service (Forest Service) issued a closure order to butterfly collecting in areas where the Mount Charleston blue butterfly occurs, thus minimizing the threat of collection (78 FR 57750). Based on information gathered from peer reviewers and the public during the comment period, we determined that it was prudent to designate critical habitat for the Mount Charleston blue butterfly (78 FR 57750).
For more information regarding our determination to designate critical habitat, please see our responses to comments in the final listing determination for Mount Charleston blue butterfly published September 19, 2013. Based on the information we received on the physical or biological features essential to the Mount Charleston blue butterfly, and information on areas otherwise essential for the subspecies, we have determined that the designation of critical habitat is prudent and determinable, and we are proposing critical habitat at this time.
Species Information
Taxonomy and Species Description
The Mount Charleston blue butterfly is a distinct subspecies of the wider ranging Shasta blue butterfly (Plebejus shasta), which is a member of the Lycaenidae family. Pelham (2008, pp. 25-26) recognized seven subspecies of Shasta blue butterflies: P. s. shasta, P. s. calchas, P. s. pallidissima, P. s. minnehaha, P. s. charlestonensis, P. s. pitkinensis, and P. s. platazul in ``A catalogue of the butterflies of the United States and Canada with a complete bibliography of the descriptive and systematic literature'' published in volume 40 of the Journal of Research on the Lepidoptera (2008, pp. 379-380). The Mount Charleston blue butterfly is known to occur only in the high elevations of the Spring Mountains, located approximately 40 kilometers (km) (25 miles (mi)) west of Las Vegas in Clark County, Nevada (Austin 1980, p. 20; Scott 1986, p. 410). The first mention of the Mount Charleston blue butterfly as a unique taxon was in 1928 by Garth (p. 93), who recognized it as distinct from the species Shasta blue butterfly (Austin 1980, p. 20). Howe (in 1975, Plate 59) described specimens from the Spring Mountains as the P. s. shasta form comstocki. However, in 1976, Ferris (p. 14) placed the Mount Charleston blue butterfly with the wider ranging Minnehaha blue subspecies. Finally, Austin asserted that Ferris had not included specimens from the Sierra Nevada Mountains of extreme western Nevada in his study, and in light of the geographic isolation and distinctiveness of the Shasta blue butterfly population in the Spring Mountains and the presence of at least three other well-
defined races (subspecies) of butterflies endemic to the area, it was appropriate to name this population as a subspecies, P. s. charlestonensis (Austin 1980, p. 20).
Our use of the genus name Plebejus, rather than the synonym Icaricia, reflects recent treatments of butterfly taxonomy (Opler and Warren 2003, p. 30; Pelham 2008, p. 265). The Integrated Taxonomic Information System (ITIS) recognizes the Mount Charleston blue butterfly as a valid subspecies based on Austin (1980) (Retrieved May 1, 2013, from the Integrated Taxonomic Information System on-line database, http://www.itis.gov). The ITIS is hosted by the United States Geological Survey (USGS) Center for Biological Informatics (CBI) and is the result of a partnership of Federal agencies formed to satisfy their mutual needs for scientifically credible taxonomic information.
As a subspecies, the Mount Charleston blue butterfly is similar to other Shasta blue butterflies, with a wingspan of 19 to 26 millimeters (mm) (0.75 to 1 inch (in)) (Opler 1999, p. 251). The Mount Charleston blue butterfly is sexually dimorphic; males and females occur in two distinct forms. The upper side of males is dark to dull iridescent blue, and females are brown with some blue basally (Opler 1999, p. 251). The species has a row of submarginal black spots on the dorsal side of the hind wing and a discal black spot on the dorsal side of the forewing and hind wing, which when viewed up close distinguishes it from other small, blue butterflies occurring in the Spring Mountains (Austin 1980, pp. 20, 23; Boyd and Austin 1999, p. 44). The underside of the wings is gray, with a pattern of black spots, brown blotches, and pale wing veins giving it a mottled appearance (Opler 1999, p. 251). The underside of the hind wing has an inconspicuous band of submarginal metallic spots (Opler 1999, p. 251). Based on morphology, the Mount Charleston blue butterfly is most closely related to the Great Basin populations of the Minnehaha blue butterfly (Austin 1980, p. 23), and it can be distinguished from other Shasta blue butterfly subspecies by the presence of a clearer, sharper, and blacker post-
median spot row on the underside of the hind wing (Austin 1980, p. 23; Scott 1986, p. 410).
Distribution
Based on current and historical occurrences or locations (Austin 1980, pp. 20-24; Weiss et al. 1997, Map 3.1; Boyd and Murphy 2008, p. 4, Pinyon 2011, Figure 9-11; Andrew et al. 2013 pp. 1-93; Thompson et al. 2014, pp. 97-158), the geographic range of the Mount Charleston blue butterfly is in the upper elevations of the Spring Mountains, centered on lands managed by the
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Forest Service in the Spring Mountains National Recreation Area of the Humboldt-Toiyabe National Forest within Upper Kyle and Lee Canyons, Clark County, Nevada. The majority of the occurrences or locations are along the upper ridges in the Mount Charleston Wilderness and in Upper Lee Canyon area, while a few are in Upper Kyle Canyon. Please refer to Table 1 of the final rule listing the Mount Charleston blue butterfly as an endangered species (78 FR 57750) for a synopsis of locations where the Mount Charleston blue butterfly has been detected since 1928.
Habitat and Biology
Weiss et al. (1997, pp. 10-11) describe the natural habitat for the Mount Charleston blue butterfly as relatively flat ridgelines above 2,500 m (8,200 ft), but isolated individuals have been observed as low as 2,000 m (6,600 ft). Boyd and Murphy (2008, p. 19) indicate that areas occupied by the subspecies feature exposed soil and rock substrates with limited or no canopy cover or shading.
Other than observations by surveyors, little information is available regarding most aspects of the subspecies' biology and the key determinants for the interactions among the Mount Charleston blue butterfly's life history and environmental conditions. Observations indicate that above- or below-average precipitation, coupled with above- or below-average temperatures, influence the phenology of this subspecies (Weiss et al. 1997, pp. 2-3 and 32; Boyd and Austin 1999, p. 8) and are likely responsible for the fluctuation in population numbers from year to year (Weiss et al. 1997, pp. 2-3 and 31-32).
Like most butterfly species, the Mount Charleston blue butterfly is dependent on specific plant species for the adult butterfly flight period (nectar plants), when breeding and egg-laying occurs, and for larval development (described under Physical and Biological Features, below (Weiss et al. 1994, p. 3; Weiss et al. 1997, p. 10; Boyd 2005, p. 1; DataSmiths 2007, p. 21; Boyd and Murphy 2008, p. 9; Andrew et al. 2013, pp. 4-12; Thompson et al. 2014, pp. 97-158)). The typical flight and breeding period for the butterfly is early July to mid-August with a peak in late July, although the subspecies has been observed as early as mid-June and as late as mid-September (Austin 1980, p. 22; Boyd and Austin 1999, p. 17; Forest Service 2006, p. 9, Thompson et al. 2014, pp. 105-116).
Like all butterfly species, both the phenology (timing) and number of Mount Charleston blue butterfly individuals that emerge and fly to reproduce during a particular year appear to be reliant on the combination of many environmental factors that may constitute a successful (``favorable'') or unsuccessful (``poor'') year for the subspecies. Specific information regarding diapause of the Mount Charleston blue butterfly is lacking, and while geographic and subspecific variation in life histories can vary, we presume information on the diapause of the closely related Shasta blue butterfly is similar to that of the Mount Charleston blue butterfly. The Shasta blue butterfly is generally thought to diapause at the base of its larval host plant or in the surrounding substrate (Emmel and Shields 1978, p. 132) as an egg the first winter and as a larva near maturity the second winter (Ferris and Brown 1981, pp. 203-204; Scott 1986, p. 411); however, Emmel and Shields (1978, p. 132) suggested that diapause was passed as partly grown larvae, because freshly hatched eggshells were found near newly laid eggs (indicating that the eggs do not overwinter). More recent observations of late summer hatched and overwintering unhatched eggs of the Mount Charleston blue butterfly eggs laid in the Spring Mountains may indicate that it has an environmentally cued and mixed diapause life cycle; however, further observations supporting egg viability are needed to confirm this (Thompson et al. 2014, p. 131).
Prolonged or multiple years of diapause has been documented for several butterfly families, including Lycaenidae (Pratt and Emmel 2010, p. 108). For example, the pupae of the variable checkerspot butterfly (Euphydryas chalcedona, which is in the Nymphalid family) are known to persist in diapause up to 5 to 7 years (Scott 1986, p. 28). The number of years the Mount Charleston blue butterfly can remain in diapause is unknown. Boyd and Murphy (2008, p. 21) suggest the Mount Charleston blue butterfly may be able to delay maturation during drought or the shortened growing seasons that follow winters with heavy snowfall and late snowmelt by remaining as eggs. Experts have hypothesized and demonstrated that, in some species of Lepidoptera, a prolonged diapause period may be possible in response to unfavorable environmental conditions (Scott 1986, pp. 26-30; Murphy 2006, p. 1; DataSmiths 2007, p. 6; Boyd and Murphy 2008, p. 22), and this has been hypothesized for the Mount Charleston blue butterfly as well (Thompson et al. 2013a, presentation). Little has been confirmed regarding the length of time or life stage in which the Mount Charleston blue butterfly diapauses.
Most butterfly populations exist as regional metapopulations (Murphy et al. 1990, p. 44). Boyd and Austin (1999, pp. 17 and 53) suggest this is true of the Mount Charleston blue butterfly. Small habitat patches tend to support smaller butterfly populations that are frequently extirpated by events that are part of normal variation (Murphy et al. 1990, p. 44). According to Boyd and Austin (1999, p. 17), smaller colonies of the Mount Charleston blue butterfly may be ephemeral in the long term, with the larger colonies of the subspecies more likely than smaller populations to persist in ``poor'' years, when environmental conditions do not support the emergence, flight, and reproduction of individuals. The ability of the Mount Charleston blue butterfly to move between habitat patches has not been studied; however, field observations indicate the subspecies has low vagility (capacity or tendency of a species to move about or disperse in a given environment), on the order of 10 to 100 m (33 to 330 ft) (Weiss et al. 1995, p. 9), and nearly sedentary behavior (DataSmiths 2007, p. 21; Boyd and Murphy 2008, pp. 3 and 9). Furthermore, movement of lycaenid butterflies, in general, is limited and on the order of hundreds of meters (Cushman and Murphy 1993, p. 40); however, there are small portions of a population that can make substantially long movements (Arnold 1983, pp. 47-48).
Based on this information, the likelihood of dispersal more than hundreds of meters is low for the Mount Charleston blue butterfly, but it may occur. Thompson et al. (2013a, presentation) have hypothesized that the Mount Charleston blue butterfly could diapause for multiple years (more than 2) as larvae and pupae until vegetation conditions are favorable to support emergence, flight, and reproduction (Thompson et al. 2013a, presentation). This could account for periodic high numbers of butterflies observed at more sites in years with favorable conditions, as was documented by Weiss et al. in 1995, than years with unfavorable conditions. Additional future research regarding diapause patterns of the Mount Charleston blue butterfly is needed to further our understanding of this subspecies.
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Critical Habitat
Background
Critical habitat is defined in section 3 of the Act as:
(1) The specific areas within the geographical area occupied by the species, at the time it is listed in accordance with the Act, on which are found those physical or biological features
(a) Essential to the conservation of the species, and
(b) Which may require special management considerations or protection; and
(2) Specific areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.
Conservation, as defined under section 3 of the Act, means to use and the use of all methods and procedures that are necessary to bring an endangered or threatened species to the point at which the measures provided pursuant to the Act are no longer necessary. Such methods and procedures include, but are not limited to, all activities associated with scientific resources management such as research, census, law enforcement, habitat acquisition and maintenance, propagation, live trapping, and transplantation, and, in the extraordinary case where population pressures within a given ecosystem cannot be otherwise relieved, may include regulated taking.
Critical habitat receives protection under section 7 of the Act through the requirement that Federal agencies ensure, in consultation with the Service, that any action they authorize, fund, or carry out is not likely to result in the destruction or adverse modification of critical habitat. The designation of critical habitat does not affect land ownership or establish a refuge, wilderness, reserve, preserve, or other conservation area. Such designation does not allow the government or public to access private lands. Such designation does not require implementation of restoration, recovery, or enhancement measures by non-Federal landowners. Where a landowner requests Federal agency funding or authorization for an action that may affect a listed species or critical habitat, the consultation requirements of section 7(a)(2) of the Act would apply, but even in the event of a destruction or adverse modification finding, the obligation of the Federal action agency and the landowner is not to restore or recover the species, but to implement reasonable and prudent alternatives to avoid destruction or adverse modification of critical habitat.
Under the first prong of the Act's definition of critical habitat, areas within the geographical area occupied by the species at the time it was listed are included in a critical habitat designation if they contain physical or biological features (1) which are essential to the conservation of the species and (2) which may require special management considerations or protection. For these areas, critical habitat designations identify, to the extent known using the best scientific and commercial data available, those physical or biological features that are essential to the conservation of the species (such as space, food, cover, and protected habitat). In identifying those physical and biological features within an area, we focus on the principal biological or physical constituent elements (primary constituent elements such as roost sites, nesting grounds, seasonal wetlands, water quality, tide, soil type) that are essential to the conservation of the species. Primary constituent elements are those specific elements of the physical or biological features that provide for a species' life-history processes and are essential to the conservation of the species.
Under the second prong of the Act's definition of critical habitat, we can designate critical habitat in areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species. We designate critical habitat in areas outside the geographical area presently occupied by a species only when a designation limited to its present range would be inadequate to ensure the conservation of the species.
Section 4 of the Act requires that we designate critical habitat on the basis of the best scientific data available. Further, our Policy on Information Standards Under the Endangered Species Act (published in the Federal Register on July 1, 1994 (59 FR 34271)), the Information Quality Act (section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 106-554; H.R. 5658)), and our associated Information Quality Guidelines, provide criteria, establish procedures, and provide guidance to ensure that our decisions are based on the best scientific data available. They require our biologists, to the extent consistent with the Act and with the use of the best scientific data available, to use primary and original sources of information as the basis for recommendations to designate critical habitat.
When we are determining which areas should be designated as critical habitat, our primary source of information is generally the information developed during the listing process for the species. Additional information sources may include the recovery plan for the species, articles in peer-reviewed journals, conservation plans developed by States and counties, scientific status surveys and studies, biological assessments, other unpublished materials, or experts' opinions or personal knowledge.
Habitat is dynamic, and species may move from one area to another over time. We recognize that critical habitat designated at a particular point in time may not include all of the habitat areas that we may later determine are necessary for the recovery of the species. For these reasons, a critical habitat designation does not signal that habitat outside the designated area is unimportant or may not be needed for recovery of the species. Areas that are important to the conservation of the species, both inside and outside the critical habitat designation, will continue to be subject to: (1) Conservation actions implemented under section 7(a)(1) of the Act, (2) regulatory protections afforded by the requirement in section 7(a)(2) of the Act for Federal agencies to ensure their actions are not likely to jeopardize the continued existence of any endangered or threatened species, and (3) section 9 of the Act's prohibitions on taking any individual of the species, including taking caused by actions that affect habitat. Federally funded or permitted projects affecting listed species outside their designated critical habitat areas may still result in jeopardy findings in some cases. These protections and conservation tools will continue to contribute to recovery of this species. Similarly, critical habitat designations made on the basis of the best available information at the time of designation will not control the direction and substance of future recovery plans, habitat conservation plans, or other species conservation planning efforts if new information available at the time of these planning efforts calls for a different outcome.
Prudency Determination
Section 4(a)(3) of the Act, as amended, and implementing regulations (50 CFR 424.12), require that, to the maximum extent prudent and determinable, the Secretary shall designate critical habitat at the time the species is determined to be an
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endangered or threatened species. Our regulations (50 CFR 424.12(a)(1)) state that the designation of critical habitat is not prudent when one or both of the following situations exist:
(1) The species is threatened by taking or other human activity, and identification of critical habitat can be expected to increase the degree of threat to the species, or
(2) such designation of critical habitat would not be beneficial to the species.
Based on information received after publication of the proposed listing rule, we determined that the threat of take attributed to collection under Factor B has been reduced with the implementation of a Forest Service closure order to limit collection in the Spring Mountains. We also determined from peer and public review of the proposed listing rule that identification and mapping of critical habitat is not expected to exacerbate the threat of collection, because location information is available on the internet and the closure order reduces the threat of collection. In the absence of finding that the designation of critical habitat would increase threats to a species, if there are any benefits to a critical habitat designation, then a prudent finding is warranted. Here, the potential benefits of designation include: (1) Triggering consultation under section 7 of the Act, in new areas for actions in which there may be a Federal nexus where it would not otherwise occur because, for example, it is or has become unoccupied or the occupancy is in question; (2) focusing conservation activities on the most essential features and areas; (3) providing educational benefits to State or county governments or private entities; and (4) preventing people from causing inadvertent harm to the species. Therefore, because we have determined that the designation of critical habitat will not likely increase the degree of threat to the species and may provide some measure of benefit, we find that designation of critical habitat is prudent for the Mount Charleston blue butterfly.
Critical Habitat Determinability
Having determined that designation is prudent, under section 4(a)(3) of the Act we must find whether critical habitat for the Mount Charleston blue butterfly is determinable. Our regulations at 50 CFR 424.12(a)(2) state that critical habitat is not determinable when one or both of the following situations exist:
(i) Information sufficient to perform required analyses of the impacts of the designation is lacking, or
(ii) The biological needs of the species are not sufficiently well known to permit identification of an area as critical habitat.
When critical habitat is not determinable, the Act allows the Service an additional year to publish a critical habitat designation (16 U.S.C. 1533(b)(6)(C)(ii)).
We reviewed the available information pertaining to the biological needs of the species and habitat characteristics where this species is located. This and other information represent the best scientific data available and led us to conclude that the designation of critical habitat is determinable for the Mount Charleston blue butterfly.
Physical or Biological Features
In accordance with section 3(5)(A)(i) and 4(b)(1)(A) of the Act and regulations at 50 CFR 424.12, in determining which areas within the geographical area occupied by the species at the time of listing to designate as critical habitat, we consider the physical or biological features that are essential to the conservation of the species and which may require special management considerations or protection. These include, but are not limited to:
(1) Space for individual and population growth and for normal behavior;
(2) Food, water, air, light, minerals, or other nutritional or physiological requirements;
(3) Cover or shelter;
(4) Sites for breeding, reproduction, or rearing (or development) of offspring; and
(5) Habitats that are protected from disturbance or are representative of the historic geographical and ecological distributions of a species.
We derive the specific physical or biological features essential to the Mount Charleston blue butterfly from studies of this species' habitat, ecology, and life history as described below. Additional information can be found in the final listing rule published in the Federal Register of September 19, 2013 (78 FR 57750). We have determined that the following physical or biological features are essential to the Mount Charleston blue butterfly:
Space for Individual and Population Growth and for Normal Behavior
The Mount Charleston blue butterfly is known to occur only in the high elevations of the Spring Mountains, located approximately 40 km (25 mi) west of Las Vegas in Clark County, Nevada (Austin 1980, p. 20; Scott 1986, p. 410). Historically, the Mount Charleston blue butterfly was detected at elevations as low as 1,830 m (6,000 ft) in the Spring Mountains (Austin 1980, p. 22; Austin 1981, p. 66; Weiss et al. 1995, p. 5). Currently, the Mount Charleston blue butterfly is presumed or known to occupy habitat occurring between 2,500 m (8,200 ft) elevation and 3,500 m elevation (11,500 ft) (Austin 1980, p. 22; Weiss et al. 1997, p. 10; Boyd and Austin 1999, p. 17; Pinyon 2011, p. 17; Andrew et al. 2013, pp. 20-61; Thompson et al. 2014, pp. 97-158). Dominant plant communities between these elevation bounds are variable (Forest Service 1998, pp. 11-12), but locations that support the Mount Charleston blue butterfly are characterized by open areas bordered, near, or surrounded by forests composed of ponderosa pine (Pinus ponderosa), Great Basin bristlecone pine (Pinus longaeva), and white fir (Abies concolor) (Andrew et al. 2013, p. 5). These open forest conditions are often created by disturbances such as fire and avalanches (Weiss et al. 1995, p. 5; DataSmiths 2007, p. 21; Boyd and Murphy 2008, pp. 23-24; Thompson et al. 2014, pp. 97-158), but the open forest conditions may also exist as a function of an area's ecological system (Provencher 2008, p. 134).
The Mount Charleston blue butterfly is described to occur on relatively flat ridgetops, gently sloping hills, or meadows, where tree cover is absent to less than 50 percent (Austin 1980, p. 22; Weiss et al. 1995, pp. 5-6; Weiss et al. 1997, pp. 10, 32-34; Boyd and Austin 1999, p. 17; Boyd and Murphy 2008, p. 19; Andrews et al. 2013, p. 3; Thompson et al. 2014, p. 138). These locations and characteristics are likely correlated with the ecological requirements of the Mount Charleston blue butterfly's larval host plants (Weiss et al. 1997, p. 22) and adult nectar plants (described below).
Therefore, based on the information above, we identify flat or gently sloping areas between 2,500 m (8,200 ft) and 3,500 m (11,500 ft) elevation in the Spring Mountains as a physical or biological feature essential to the Mount Charleston blue butterfly for space for individual and population growth and for normal behavior.
Food, Water, Air, Light, Minerals, or Other Nutritional or Physiological Requirements
The best scientific information available regarding food, water, air, light, minerals, and other nutritional or physiological requirements of the Mount Charleston blue butterfly's life stages (egg, larva, pupa, adult) result from observations by surveyors, and research to determine the requirements and environmental conditions essential to the Mount Charleston blue butterfly.
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In general, resources that are thought to fulfill these requirements occur in open areas with exposed soil and rock substrates with short, widely spaced forbs and grasses. These areas allow light to reach the ground in order for adult nectar and larval host plants to grow.
Adult Mount Charleston blue butterflies have been documented feeding on nectar from a number of different flowering plants, but most frequently these species are Erigeron clokeyi (Clokey's fleabane), Eriogonum umbellatum var. versicolor (sulphur-flower buckwheat), Hymenoxys cooperi (Cooper rubberweed), and Hymenoxys lemmonii (Lemmon bitterweed) (Weiss et al. 1997, p. 11; Boyd and Murphy 2008, pp. 13, 16; Pinyon 2011, p. 17; Andrew 2013, pp. 3-4; Thompson et al. 2014, pp. 117-118). Densities of nectar plants generally occur at more than 2 per square meter (m\2\) (20 per square foot (ft\2\)) for smaller plants such as E. clokeyi and more than 0.1 per m\2\ (1 per ft\2\) for larger and taller plants such as Hymenoxys sp. and E. umbellatum (Thompson et al. 2014, p. 138). Nectar plants typically occur within 10 m (33 ft) of larval host plants and in combination provide nectar during the adult flight period between mid-July and early August (Thompson et al. 2014, p. 138). Other species which adult Mount Charleston blue butterflies have been documented using as nectar plants include Antennaria rosea (rosy pussy toes), Cryptantha species (cryptantha; the species C. angustifolia originally reported is likely a misidentification because this species occurs in much lower elevation desert habitat (Niles and Leary 2007, p. 26)), Ericameria nauseosa (rubber rabbitbrush), Erigeron flagellaris (trailing daisy), Guiterrezia sarothrae (broom snake weed), Monardella odoratissima (horsemint), Petradoria pumila var. pumila (rock-goldenrod), and Potentilla concinna var. concinna (Alpine cinquefoil) (Boyd and Murphy 2008, pp. 13, 16; Thompson et al. 2014, pp. 117-118).
Based on surveyors' observations, several species appear to be important food plants for the larval life stage of the Mount Charleston blue butterfly. Therefore, we consider those plants on which surveyors have documented Mount Charleston blue butterfly eggs to be larval host or food plants (hereafter, referred to as larval host plants). Based on this, Astragalus calycosus var. calycosus, Oxytropis oreophila var. oreophila, and Astragalus platytropis are all considered larval host plants for the Mount Charleston blue butterfly (Weiss et al. 1997, p. 10; Austin and Leary 2008, p. 86; Andrew et al. 2013, pp. 7-8; Thompson et al. pp. 121-131) (See Sites for Breeding, Reproduction, or Rearing (or Development) of Offspring below for more details). Note that in the final listing rule for the Mount Charleston blue butterfly (78 FR 57750; September 19, 2013) we reported Astragalus lentiginosus var. kernensis (Kern plateau milkvetch) as a larval host plant (Andrew et al. 2013, p. 3); however, this host plant was subsequently determined to be Oxytropis oreophila var. oreophila (mountain oxytrope) (Thompson et al. 2014, pp. 97-158), and has been described as such in this final rule. Future surveys and research may document the importance of other plant species as food resources for Mount Charleston blue butterfly larvae. Densities of host plants are generally greater than two per m\2\ (20 per ft\2\) (Weiss 1997, p. 34; Andrew et al. 2013, p. 9; Thompson et al. 2014, p. 138).
In addition, the Mount Charleston blue butterfly requires open canopy cover (open forest). Specifically, the Mount Charleston blue butterfly requires areas where tree cover is absent or low. This may be due to ecological requirements of the larval host plants or adult nectar plants or due to the flight behavior of the Mount Charleston blue butterfly. As with most butterflies, the Mount Charleston blue butterfly typically flies during sunny conditions, which are particularly important for this subspecies given the cooler air temperatures at high elevations in the Spring Mountains of Nevada (Weiss et al. 1997, p. 31).
The areas where the Mount Charleston blue butterfly occurs often have shallow exposed soil and rock substrates with short, widely spaced forbs and grasses (Weiss et al. 1997, pp. 10, 27, and 31; Boyd 2005, p. 1; Service 2006a, p. 1; Kingsley 2007, pp. 9-10; Boyd and Murphy 2008, p. 19; Pinyon 2011, pp. 17, 21; Andrew et al. 2013, pp. 9-13; Thompson et al. 2014, pp. 137-143). These vegetative characteristics may be important as they would not impede the Mount Charleston blue butterfly's low flight behavior (Weiss et al. 1997, p. 31) (reported to be 15 centimeters (cm) (38 in) or less (Thompson et al. 2014, p. 118)). Some taller grass or forb plants may be present when their density is less than five per m\2\ (Thompson et al. 2014, pp. 138-139).
Therefore, based on the information above, we identify open habitat that permits light to reach the ground, nectar plants for adults and host plants for larvae, and exposed soil and rock substrates with short, widely spaced forbs and grasses to be physical or biological features for this subspecies that provide food, water, air, light, minerals, or other nutritional or physiological requirements.
Cover or Shelter
The study and delineation of habitat for many butterflies has often been associated with larval host plants, breeding resources, and nectar sources for adults (Dennis 2004, p. 37). Similar to other butterfly species (Dennis 2004, p. 37), there is little to no information available about the structural elements required by the Mount Charleston blue butterfly for cover or shelter. However, we infer that, because of their low vagility, cover or shelter used by any life stage of the Mount Charleston blue butterfly will be in close association or proximity to larval or adult food resources in its habitat.
For larvae, diapause is generally thought to occur at the base of the larval host plant or in the surrounding substrate (Emmel and Shields 1978, p. 132). Mount Charleston blue butterfly larvae feed after diapause. Like other butterflies, after larvae become large enough, they pupate (Scott 1986, p. 24). Pupation most likely occurs in the ground litter near a main stem of the larval host plant (Emmel and Shields 1978, p. 132). After pupation, adults feed and mate in the same areas where larvae diapause and pupation occurs. In addition, no specific areas for overnight roosting by adult Mount Charleston blue butterflies have been reported. However, adults have been observed using areas in moderately dense forest stands immediately adjacent to low-cover areas with larval host and nectar plants (Thompson et al. 2014, p. 120).
Therefore, based on the information above, we identify areas with larval host plants and adult nectar plants, and areas immediately adjacent to these plants, to be a physical or biological feature for this subspecies that provides cover or shelter.
Sites for Breeding, Reproduction, or Rearing (or Development) of Offspring
The Mount Charleston blue butterfly has specific site requirements for its flight period when breeding and reproduction occur, and these requirements may be correlated to its limited vagility and short lifespan. The typical flight and breeding period for the Mount Charleston blue butterfly is early July to mid-August with a peak in late July, although the subspecies has been observed as early as mid-
June and as late as mid-September (Austin 1980, p. 22; Boyd and Austin 1999, p. 17; Forest Service 2006, p. 9; Thompson et al. 2014, pp. 104-
116). Breeding
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opportunities for individual Mount Charleston blue butterflies are presumably short in duration during its lifespan, which may range from 2 to 12 days, as has been reported for other closely related species (Arnold 1983, Plebejinae in Table 44). Therefore, the Mount Charleston blue butterfly may generally be constrained to areas where adult nectar resources are in close proximity to plants on which to breed and lay eggs. Researchers have documented Mount Charleston blue butterfly breeding behavior in close spatial association with larval host and adult nectar plants (Thompson et al. 2014, pp. 121-125).
The presence of Mount Charleston blue butterfly adult nectar plants, such as Erigeron clokeyi, appears to be strongly associated with its larval host plants (Andrew et al. 2013, p. 9). Female Mount Charleston blue butterflies have been observed ovipositing a single egg per host plant, which appears to weakly adhere to the host plant surface; this has been observed most typically within basal leaves (Thompson et al. 2014, p. 129). Ovipositing by butterflies on plants is not absolute evidence of larval feeding or survival (Austin and Leary 2008, p. 1), but may provide a stronger inference in combination with close adult associations and repeated observations. Presuming the Mount Charleston blue butterfly's diapause behavior is similar to the closely related Shasta blue butterfly, the Mount Charleston blue butterfly diapauses as an egg or as a larva at the base of its egg and larval host plants or in the surrounding substrate (Emmel and Shields 1978, p. 132; Ferris and Brown 1981, pp. 203-204; Scott 1986, p. 411).
In 1987, researchers documented two occasions when Mount Charleston blue butterflies oviposited on Astragalus calycosus var. calycosus (= var. mancus) (Austin and Leary 2008, p. 86). Based on this documentation and subsequent observations of adult Mount Charleston blue butterflies, Astragalus calycosus var. calycosus was the only known larval host plant for the Mount Charleston blue butterfly (Austin and Leary 2008, p. 86). In 2011 and 2012, researchers from the University of Nevada Las Vegas observed female Mount Charleston blue butterflies landing on and ovipositing on Oxytropis oreophila var. oreophila (mountain oxytrope) and Astragalus platytropis (broadkeeled milkvetch), which presumably also function as larval host plants (Andrew et al. 2013, pp. 4-12; Thompson et al. 2014, pp. 122-134). Andrew et al. (2013, p. 5) also documented Mount Charleston blue butterfly eggs on all three plant species. Other subspecies of Shasta blue butterflies have been reported to use more than one plant during larval development, including Astragalus platytropis (Austin and Leary 2008, pp. 85-86). Because the subspecies has been documented ovipositing on these three plant species and other subspecies of Shasta blue butterflies are known to use multiple larval host plants, we consider Astragalus calycosus var. calycosus, Oxytropis oreophila var. oreophila, and Astragalus platytropis to be the host plants used during Mount Charleston blue butterfly larval development.
Therefore, based on the information above, we identify areas with larval host plants, especially Astragalus calycosus var. calycosus, Oxytropis oreophila var. oreophila, or Astragalus platytropis, and adult nectar plants, especially Erigeron clokeyi, Eriogonum umbellatum var. versicolor, Hymenoxys cooperi, and Hymenoxys lemmonii, during the flight period of the Mount Charleston blue butterfly to be a physical or biological feature for this subspecies that provides sites for breeding, reproduction, or rearing (or development) of offspring.
Habitats That Are Protected From Disturbance or are Representative of the Historical, Geographical, and Ecological Distributions of the Subspecies
Habitat for the Mount Charleston blue butterfly that is protected from disturbance or representative of the historical, geographical, and ecological distributions of the subspecies occurs in locations with limited canopy cover that comprise the appropriate species of larval host and adult nectar plants. Although some of these open locations occur due to wind and other environmental stresses that inhibit tree and shrub growth, fire is one of the most prevalent disturbances across the landscape of the Mount Charleston blue butterfly. To better understand the fire frequency and severity at Mount Charleston blue butterfly locations, we characterized fire regimes at these locations using condition classes developed by Provencher (2008, Appendix II; Barrett et al. 2010, p. 15). Fire regime condition classes are classified by fire frequency, which is the average number of years between fires, and fire severity, which represents the percent replacement of dominant overstory vegetation (Barrett et al. 2010, p. 15). Fire regimes can be broadly categorized for Mount Charleston blue butterfly locations based on elevation. Higher elevation locations, generally above 2,740 m (9,000 ft) elevation, occur in fire regime condition classes 4 and 5 (Provencher 2008, Appendix II). Lower elevation locations, generally below 2,740 m (9,000 ft), occur in fire regime condition classes 2 and 3 (Provencher 2008, Appendix II).
In higher elevation locations where the Mount Charleston blue butterfly is known or presumed to occur (South Loop Trail, Mummy Springs, upper Bonanza Trail, and Griffith Peak), disturbance from fire is relatively infrequent, with variable severity (fire regime condition classes 4 and 5 in Provencher 2008, Appendix II), occurring every 35 to 200 years at a high severity, or occurring more frequently than every 200 years with a variable but generally high severity (Barrett et al. 2010, p. 15). Other disturbances likely to occur at the high-elevation Mount Charleston blue butterfly locations are from wind and other weather phenomena (Provencher 2008, Appendix II). At these high-
elevation habitats, fire frequency and severity are relatively similar to historic regimes (Provencher 2008, Table 4, 5 and Appendix II), so vegetation succession should be within the normal range of variation. Vegetation succession at some high-elevation areas that currently lack trees may cause these areas to become more forested, but other areas that are scoured by wind or exposed to other severe environmental stresses may remain non-forested (for example, South Loop Trail; Andrew et al. 2013, pp. 20-27) (Provencher and Anderson 2011, pp. 1-116; NVWAP 2012, p. 177). Thus, we expect higher elevation locations will be able to continue to provide open areas with the appropriate vegetation necessary to support individuals and populations of Mount Charleston blue butterflies.
In contrast, at lower elevation locations where the Mount Charleston blue butterfly is known or presumed to occur (Las Vegas Ski and Snowboard Resort (LVSSR), Foxtail, Youth Camp, Gary Abbott, Lower LVSSR Parking, Lee Meadows, Bristlecone Trail, and lower Bonanza Trail), disturbance from fire is likely to occur less than every 35 years with more than 75 percent being high-severity fires, or is likely to occur more than every 35 years at mixed-severity and low-severity (fire regime condition classes 2 and 3 in Provencher 2008, Appendix II). At these lower elevation habitats, fire frequency and severity appear to have departed from historic regimes (Provencher 2008, Table 4, 5 and Appendix II). Lack of fire due to fire exclusion or reduction in natural fire cycles as has been demonstrated in the Spring Mountains (Entrix 2008, p. 113) and other proximate mountain ranges (Amell 2006, pp. 2-3), has likely resulted in long-term successional changes, including increased forest area
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and forest structure (higher canopy cover, more young trees, and more trees intolerant of fire) (Nachlinger and Reese 1996, p. 37; Amell 2006, pp. 6-9; Boyd and Murphy 2008, pp. 22-28; Denton et al. 2008, p. 21; Abella et al. 2012, pp. 128, 130) at these lower elevation locations. Without fire in some of these locations, herbs and small forbs may be nearly absent as the vegetation moves towards later successional classes with increasing tree overstory cover (Provencher 2008, Appendix II). Therefore, habitat at the lower elevation Mount Charleston blue butterfly locations is more dissimilar from what would be expected based on historic fire regimes (Provencher 2008, Table 4, 5 and Appendix II). Thus, in order for Mount Charleston blue butterfly individuals and populations to be maintained at lower elevation locations, active habitat management will likely be necessary.
In July 2013, the Carpenter 1 Fire burned into habitat of the Mount Charleston blue butterfly along the ridgelines between Griffith Peak and South Loop spanning a distance of approximately 3 miles (5 km). Within this area there are low-, moderate-, or high-quality patches of Mount Charleston blue butterfly habitat intermixed with non-habitat. The majority of Mount Charleston blue butterfly moderate- or high-
quality habitat through this area was classified as having a very low or low soil-burn severity (Kallstrom 2013, p. 4). The characteristics of Mount Charleston blue butterfly habitat in this area of widely spaced grass and forbs, exposed soil and rocks, and low tree canopy cover result in lower fuel loading and continuity, which likely contributed to its low burn severities. While areas of moderate- and high-quality Mount Charleston blue butterfly habitat may have had a very low or low soil-burn severity rating, it is unknown to what extent butterflies in egg, larval, pupal, or adult life stages were exposed to lethal levels of smoke, gases, and convection or radiant heat from the fire. Until surveys are performed on the ground, damage to larval host and adult nectar plants in unburned, very low or low soil-burn severity areas cannot be determined. Butterflies in an adult life stage may have been able to escape the fire.
Areas with the highest observed concentrations of Mount Charleston blue butterflies in moderate- and high-quality habitat were outside the fire perimeter in an area slightly lower in elevation, below a topographic crest, and may have been unaffected by heat and smoke from the fire. Butterflies in these areas may have received topographic protection with rising smoke and convective heat moving above them; however, it is unknown if they were exposed to lethal radiant heat. Life stages of the butterfly low to the ground, in the soil, or among the rocks also may have been afforded some protection from the smoke and heat.
Areas of lower quality habitat appear to have had higher tree-
canopy cover and generally experienced low to moderate soil-burn severity. Only a small percentage of documented Mount Charleston blue butterfly locations occurred in these areas. Some effects of the fire may improve habitat for the Mount Charleston blue butterfly in the long term by opening the tree canopy, providing additional areas for larval host and nectar plants to grow, and releasing stored nutrients; however, improvements will depend upon successional conditions, such as soil types and moisture, and seed sources.
Recreational activities, trail-associated erosion, and the introduction of weeds or invasive grasses are likely the greatest threats that could occur within areas of Mount Charleston blue butterfly habitat burned by the Carpenter 1 Fire. Other potential threats to the Mount Charleston blue butterfly habitat associated with the fire may include trampling or grazing of new larval host or nectar plants by wild horses (Equus ferus) and elk (Cervus elaphus). However, use of this Mount Charleston blue butterfly habitat in these watersheds by wild horses and elk is currently very low.
Effects on the Mount Charleston blue butterfly or its habitat from climate change will vary across its range because of topographic heterogeneity (Luoto and Heikkinen 2008, p. 487). The Intergovernmental Panel on Climate Change (IPCC) has high confidence in predictions that extreme weather events, warmer temperatures, and regional drought are very likely to increase in the northern hemisphere as a result of climate change (IPCC 2007, pp. 15-16). Climate models show the southwestern United States has transitioned into a more arid climate of drought that is predicted to continue into the next century (Seager et al. 2007, p. 1181). In the past 60 years, the frequency of storms with extreme precipitation has increased in Nevada by 29 percent (Madsen and Figdor 2007, p. 37). Changes in local southern Nevada climatic patterns cannot be definitively tied to global climate change; however, they are consistent with IPCC-predicted patterns of extreme precipitation, warmer than average temperatures, and drought (Redmond 2007, p. 1). Therefore, we believe that climate change will impact the Mount Charleston blue butterfly and its high-elevation habitat through predicted increases in extreme precipitation and drought. Alternating extreme precipitation and drought may exacerbate threats already facing the subspecies as a result of its small population size and threats to its habitat.
Based on the information above, we identify habitat where natural disturbance, such as fire which creates and maintains openings in the canopy (fire regime condition classes 2, 3, 4, and 5), to be a physical or biological feature for this subspecies that provides habitats that are representative of the historical, geographical, and ecological distributions of the subspecies.
Primary Constituent Elements for Mount Charleston Blue Butterfly
Under the Act and its implementing regulations, we are required to identify the physical or biological features essential to the conservation of Mount Charleston blue butterfly in areas occupied at the time of listing, focusing on the features' primary constituent elements. We consider primary constituent elements to be those specific elements of the physical or biological features that provide for a species' life-history processes and are essential to the conservation of the species.
Based on our current knowledge of the physical or biological features and habitat characteristics required to sustain the species' life-history processes, we determine that the primary constituent elements specific to Mount Charleston blue butterfly are:
(1) Areas of dynamic habitat between 2,500 m (8,200 ft) and 3,500 m (11,500 ft) elevation with openings or where disturbance provides openings in the canopy that have no more than 50 percent tree cover (allowing sunlight to reach the ground), widely spaced low (
