Daily Rules, Proposed Rules, and Notices of the Federal Government
We request that you send comments only by the methods described above. We will post all comments on
We designated critical habitat for this species in 2005. As part of a settlement agreement, we agreed to reconsider the designation, and published a proposed revised designation for the Buena Vista Lake shrew in the
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. We will accept written comments and information during this reopened comment period on the revisions herein as well as the proposed revised designation of critical habitat for the Buena Vista Lake shrew that was published in the
We request comments or information from other concerned government agencies, the scientific community, industry, or any other interested party concerning the proposal to revise the designation of critical habitat for the Buena Vista Lake shrew, as revised herein. 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
(2) Specific information on:
(a) The amount and distribution of Buena Vista Lake shrew 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) Areas identified in this revision to the proposal to revise critical habitat that should not be proposed as critical habitat and why.
(3) Land use designations and current or planned activities in the subject areas and their possible impacts on proposed revised critical habitat.
(4) Information on the projected and reasonably likely impacts of climate change on the Buena Vista Lake shrew and proposed revised critical habitat.
(5) Information that may assist us in identifying or clarifying the physical and biological features essential to the conservation of the Buena Vista Lake shrew, especially as they relate to habitat conditions for the Buena Vista Lake shrew at Atwell Island, Tulare County.
(6) Any probable economic, national security, or other relevant impacts of designating any area that may be included in the final designation; in particular, any impacts on small entities or families, and the benefits of including or excluding areas that exhibit these impacts.
(7) Specific information on the taxonomy of the Buena Vista Lake shrew, especially in relationship to the adorned, or Southern California, ornate shrew (
(8) 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.
(9) Whether the potential exclusion of the Kern Fan Recharge Unit (Unit 3) under section 4(b)(2) of the Act, which is covered by the Buena Vista Lake Shrew Special Management Plan for Kern Fan Water Recharge Site, and Addendum, from final critical habitat is or is not appropriate, whether the benefits of excluding any specific area outweigh the benefits of including that area as critical habitat and why, and whether such an exclusion may or may not lead to the species' extinction.
(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
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Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on
It is our intent to discuss only those topics directly relevant to the designation of critical habitat in this proposed rule. In a July 9, 2009, settlement agreement, the Service agreed to publish a new proposal of critical habitat for the species which encompassed the same geographic area as the August 19, 2004 (69 FR 51417) proposed designation. On October 21, 2009, the
A summary of the information that is relevant to this revised proposed critical habitat designation is provided below. For more information on previous Federal actions concerning the Buena Vista Lake shrew, refer to the proposed revised designation of critical habitat published in the
The Buena Vista Lake shrew (
Grinnell (1932) was the first to describe the Buena Vista Lake shrew as a new subspecies, based on the type specimen and two other specimens collected around the old Buena Vista Lake bed. A single specimen of the shrew had previously been collected in October 1909, at Buttonwillow, a town approximately 25 miles (mi) (40 kilometers (km)) northwest of Buena Vista Lake (Williams 1986, p. 13; Long 1998, p. 1; California Academy of Sciences 2012). According to Grinnell's description, the Buena Vista Lake shrew's back is predominantly black with a buffy-brown speckling pattern, its sides are more buffy-brown than the upper surface, and its underside is smoke-gray. The tail is faintly bicolor and blackens toward the end both above and below. The Buena Vista Lake shrew differs from its geographically closest subspecies, the adorned ornate shrew (
Grinnell (1932, p. 390) noted evidence that integration between the adorned and the Buena Vista Lake shrew subspecies occurred in areas of geographic overlap. This integration prompted Freas (1990, pp. 2, 3) to question the legitimacy of the Buena Vista Lake shrew's status as a subspecies distinct from the broader-ranging adorned ornate shrew. Since the 1990s, the
Ornate shrews, on the average, rarely live longer than 12 months, and evidence indicates that the normal lifespan does not exceed 16 months (Rudd 1955, p. 328). The Buena Vista Lake shrew has a breeding season that begins in February or March, and may either extend later in the year, based on habitat quality and availability of water, or end with the onset of the dry season in May or June (Maldonado 1998). The majority of females give birth in the spring, and produce a single litter containing four to six young. Within a population, the number of litters produced per year depends on how early or late in the year the young are born; adults are sexually active in spring, while some young-of-the-year that are born early in the year become sexually active by late summer (Owen and Hoffmann 1983, p. 4). Because the life expectancy of most shrews is 12 to 16 months (Rudd 1955, p. 328), most individuals probably produce no more than two litters in their lifetime, with population replacement occurring annually (Collins 1998).
Shrews are primarily insectivorous. Due to their high rate of metabolism relative to their capacity for energy storage (McNab 1991, p. 35), they must eat more than their own weight each day (Burt and Grossenheider 1964, p. 3) in order to withstand starvation and maintain their body weight. Shrews in this family can have an impact on surrounding plant communities by consuming large quantities of insects, slugs, and other invertebrates that can influence such things as plant succession and the irruptions (population dynamics) of pest insects (Williams 1991, p. 1). The Buena Vista Lake shrew also may be an important prey species for raptors, snakes, and mammalian predators, such as foxes and skunks (Maldonado 1992, p. 7).
The Buena Vista Lake shrew was likely historically distributed in the marshlands of the San Joaquin Valley throughout most of the Tulare Basin (Grinnell 1933, p. 83). The Tulare Basin, essentially occupying the southern half of the San Joaquin Valley, had no regular outlet to the ocean and contained Buena Vista, Kern, and Tulare Lakes. These lakes were fed by the Kern, Kaweah, Tule, and Kings rivers and their tributaries, and were interconnected by hundreds of square miles of tule marshes and other permanent and seasonal lakes, wetlands, and sloughs (Williams and Harpster 2001, p. 13). Tulare Lake was the largest freshwater lake in the United States west of the Mississippi River. However, by the time the Buena Vista Lake shrew was discovered, the beds of these lakes were already dry and mostly cultivated, with only sparse remnants of the original fauna (Grinnell 1932, p. 1). Today the lakes and wetlands have been drained and converted into irrigated agricultural fields, though portions of
As discussed in detail in the Critical Habitat section below, the Buena Vista Lake shrew is closely associated with dense, riparian understories that provide food, cover, and moisture (Maldonado 1992, p. 5). Moisture is required to support a diverse insect fauna, which is the primary food source needed to maintain the Buena Vista Lake shrew's high metabolism. During surveys conducted at Kern Lake Preserve in 1988 and 1990, Freas (1990, p. 8) found that the Buena Vista Lake shrew preferred mesic (moderately moist) habitats over xeric (drier) habitats, with 25 animals being captured in the mesic environments and none in xeric habitat. Maldonado (1992, p. 5) also acknowledged this type of habitat preference, stating that the Buena Vista Lake shrew is closely associated with dense, riparian understories that provide food, cover, and moisture. He also noted that moist soil in areas with an overstory of willows or cottonwoods appears to be favored, but may not be an essential habitat feature (Williams and Harpster 2001, p. 13; Maldonado 2011).
The mesic, lower elevation range of the Buena Vista Lake shrew is almost completely surrounded by the semi-arid, higher elevation range of the adorned ornate shrew (Grinnell 1933, pp. 82, 83; Hall 1981, p. 38; Owen and Hoffman 1983, p. 2: Maldonado
At the time of listing, the Buena Vista Lake shrew was identified as occurring in four isolated locations along an approximately 70-mile (mi) (113-kilometer (km)) stretch on the west side of the Tulare Basin: At the former Kern Lake Preserve on the old Kern Lake bed, the Kern Fan water recharge area, Coles Levee, and the Kern National Wildlife Refuge (Kern NWR) (67 FR 10101; March 6, 2002). By the time that critical habitat was proposed in 2004, a fifth occurrence of the Buena Vista Lake shrew had been identified at the historical lake bed of Goose Lake. During the same general period, continuing surveys of riparian and upland habitat resulted in capture of ornate shrews at several additional locations within the Tulare Basin, including Kern, Kings, and Tulare Counties, although the shrews were not identified to the subspecies level (Williams and Harpster 2001, p. 14; Endangered Species Recovery Program (ESRP) 2005, p. 1; Maldonado 2006, p. 5). In 2011, during our 5-year status review of the Buena Vista Lake shrew, we obtained additional information indicating that the shrews at these localities would be considered Buena Vista Lake shrews (Williams and Harpster 2001, p. 16; Maldonado 2011; Service 2011, pp. 6-9). Two of the occurrences (Lemoore and Semitropic Ecological Preserve (also known as Main Drain or Chicca and Sons)) are located within general riparian and wetland habitat known to be suitable for the Buena Vista Lake shrew; however, the third location (Atwell Island) does not match the habitat that has previously been described for the shrew and does not contain the physical or biological features identified as essential for the conservation of the Buena Vista Lake shrew (see Critical Habitat section). Additional information below describes what is now known about the Buena Vista Lake shrew at these locations.
At the time of publication of our 5-year review, surveys for Buena Vista Lake shrews had been conducted at 21 sites and the Buena Vista Lake shrew had been determined to be present in 8 of the sites (Williams and Harpster 2001, pp. 8-14; ESRP 2005, p. 1; Maldonado 2006, p. 5; Cypher 2010). Although shrews at the Semitropic, Lemoore, and Atwell Island locations had not been previously identified to subspecies in Maldonado 2006, communication between Service staff and species experts classified them as Buena Vista Lake shrews (Maldonado 2011). Trapping for Buena Vista Lake shrews has also been completed on the Tule Elk Preserve, Pixley National Wildlife Refuge (NWR), Lake Woollomes, the Nature Conservancy's Paine Wildflower Preserve, the Kern Water Bank, the Voice of America site west of Delano, Kern River Parkway, a parcel between Kern and Buena Vista Lakes owned by the Bureau of Land Management (BLM), the Buena Vista Lake Recreation Area, and Wind Wolves Preserve.
No shrews were detected at any location (Williams 1986, p. 3; Williams and Harpster 2001, pp. 6-12), with the exception of the Wind Wolves Preserve. However, the shrews detected at Wind Wolves Preserve are expected to be adorned ornate shrews based on mitochondrial DNA analysis of one tissue sample available from that location (Maldonado 2006, pp. 9, 16-19; Cypher 2010, p. 1; Maldonado 2011, pp. 1, 2). Several areas north of the Tulare Lake bed, including Tranquility, Helm, and the Los Banos Wildlife Area, hosted extremely high numbers of ornate shrews in several successful trapping outings, but the shrews collected in those locations were also likely to be the adorned ornate shrew, based on analysis of mitochondrial DNA and microsatellites.(Maldonado 2006, pp. 16-19; Maldonado 2011, pp. 1, 2).
In 1999 and 2000, shrews, which were not identified to subspecies, were captured during a restoration study on a farmland site that had been recently retired at the BLM Atwell Island site, located approximately 2 mi (3.2 km) south of Alpaugh in Tulare County. As described above, these shrews have recently been determined to be Buena Vista Lake shrews; however, the habitat in which they've been located does not match their known wetland habitat. In 1999, most of the captures were on ground that was planted to sugar beets and cotton the previous year. Between 1999 and 2000, a cover crop of barley was planted and harvested on most of the acreage, while a small portion of the area had been fallow longer than 5 years and had a cover of weedy, mostly exotic, annual plants (Williams and Harpster 2001, p. 13). The area has had a long history of irrigated agriculture, with the site surrounded by intensively farmed, irrigated cropland, thus indicating that the location did not match the available descriptions of Buena Vista Lake shrew habitat.
Because shrews were found in an atypical location, surrounded by intensively farmed, irrigated cropland, their discovery led to speculation that the shrews either were able to persist on site during cultivation of irrigated row crops or dispersed to the site after it was fallowed (Williams and Harpster 2001, pp. 13, 14). Although the site is located within an area that was historically classified as wetland, there is no wetland or riparian vegetation in the areas in which the shrews were found and the nearest water source is over three-quarters of a mile (1.2 km) to the north. The lack of typical shrew habitat components, such as standing water and dense riparian vegetation, have left us to speculate that shrews may persist here due to relatively localized deep cracks in the particular clay soils present in this portion of Atwell Island and the abundance of rodent burrows also present here, both of which may provide additional moisture, invertebrate prey, and cover for the shrews. Currently, this occurrence represents an anomaly that does not correspond to the common
Since the designation of critical habitat in 2005, additional genetic analysis has been conducted to evaluate the patterns of genetic variation within the ornate shrew complex, including the Buena Vista Lake shrew, in the central and southern San Joaquin Valley (Maldonado 2006, p. 16).
On October 21, 2009, the Service published a revised proposed designation of critical habitat for the Buena Vista Lake shrew (74 FR 53999) encompassing the same geographic area as the August 19, 2004 (69 FR 51417), proposed designation. The Service published a document on April 28, 2011 (76 FR 23781), announcing the reopening of the comment period for the revised proposed critical habitat designation, the associated draft economic analysis, and the amended required determinations. This document also announced a public hearing, which was held in Bakersfield, California, on June 8, 2011. On March 6, 2012, the Service was granted an extension by the Court to consider additional information on the shrew that was identified during the 5-year review process (
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 geographic 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 the elements of physical or biological features that 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 geographic 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. For example, an area currently occupied by the species but that was not occupied at the time of listing may be essential to the conservation of the species and may be included in the critical habitat designation. We designate critical habitat in areas outside the geographic area occupied by a species only when a designation limited to its 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
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) the prohibitions of section 9 of the Act if actions occurring in these areas may affect the species. 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 (HCPs), or other species conservation planning efforts if new information available at the time of these planning efforts calls for a different outcome.
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 geographic 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 historical, geographic, and ecological distributions of a species.
We derive the specific physical or biological features required for the shrew from studies of the species habitat, ecology, and life history as described below. Additional information can be found in the final listing rule published in the
Historically, the Buena Vista Lake shrew was recorded in association with perennial and intermittent wetland habitats along riparian corridors, marsh edges, and other palustrine (marsh type) habitats in the southern San Joaquin Valley of California. The shrew presumably occurred in the moist habitat surrounding wetland margins in the Kern, Buena Vista, Goose, and Tulare Lakes on the valley floor below elevations of 350 feet (ft) (107 meters (m)) (Grinnell 1932 p. 389; Hall 1981 p. 38; Williams and Kilburn 1984 p. 953; Williams 1986 p. 13; Service 1998 p. 163). With the draining and conversion of the majority of the Buena Vista Lake shrew's natural habitat from wetland to agriculture, and the channelization of riparian corridors for water conveyance structures, the vegetative communities associated with the Buena Vista Lake shrew were lost or degraded, and nonnative plant species replaced those associated with the shrew (Grinnell 1932 p. 389; Mercer and Morgan 1991 p. 9; Griggs 1992 p. 11; Service 1998 p. 163). Open water does not appear to be necessary for the survival of the shrew. The habitat where the shrew has been found contains areas with both open water and mesic environments (Maldonado 1992 p. 3; Williams and Harpster 2001 p. 12). However, the availability of water contributes to improved vegetation structure and diversity, which improves cover availability. The presence of water also attracts potential prey species, improving prey diversity and availability.
Current survey information has identified eight areas where the Buena Vista Lake shrew has been found in recent years (Maldonado 2006 p. 16; Williams and Harpster 2001 p. 1; ESRP 2005 p. 11): the former Kern Lake Preserve (Kern Preserve) on the old Kern Lake bed, the Kern Fan water recharge area, Coles Levee Ecological Preserve (Coles Levee), the Kern National Wildlife Refuge (Kern NWR), the Goose Lake slough bottoms (Goose Lake), the Atwell Island land retirement demonstration site (Atwell Island), the Lemoore Wetland Reserve, and the Semitropic Ecological Reserve (also known as Main Drain or Chicca and Sons). Based on changes in the native habitat composition and structure, and descriptions of the habitat where the Buena Vista Lake shrew have been found, we identify habitat adjacent to, or within, a matrix of perennial and intermittent wetland habitats along riparian corridors, marsh edges, and other palustrine (marsh type) habitats as physical features that are needed by the Buena Vista Lake shrew.
The specific feeding and foraging habits of the Buena Vista Lake shrew are not well known. In general, shrews primarily feed on insects and other animals, mostly invertebrates (Harris 1990 p. 2; Maldonado 1992 p. 6). Food
The vegetation communities described above provide a diversity of structural layers and plant species and likely contribute to the availability of prey for shrews. Therefore, conservation of the shrew should include consideration of the habitat needs of prey species, including structural and species diversity and seasonal availability. Shrew habitat must provide sufficient prey base and cover from which to hunt in an appropriate configuration and proximity to nesting sites. The shrew feeds indiscriminately on available larvae and adults of several species of aquatic and terrestrial insects. An abundance of invertebrates is associated with moist habitats, such as wetland edges, riparian habitat, or edges of lakes, ponds, or drainages that possess a dense vegetative cover (Owen and Hoffmann 1983 p. 3). Therefore, based on the information above, we identify a consistent and diverse supply of invertebrate prey to be an essential component of the biological features essential for the conservation of the Buena Vista Lake shrew.
The vegetative communities associated in general with Buena Vista Lake shrew occupancy are characterized by the presence of (but are not limited to):
The communities in which Buena Vista Lake shrews have primarily been found are characterized by dense mats of leaf litter or herbaceous vegetation. The insect prey of the shrew also thrives in the dense matted vegetation. Although shrews have also been found at Atwell Island, in an area largely devoid of vegetation but characterized by deep cracks in the soils, little is currently known of the shrew or habitat needs at this site.
The Buena Vista Lake shrew is preyed upon by small mammalian predators as well as by avian predators (Maldonado 1992, p. 7). Dense vegetative structure provides the cover or shelter essential for evading predators. It also serves as habitat for breeding and reproduction, and allows for the protection and rearing of offspring and the growth of adult shrews. Therefore, based on the information above, we identify riparian and wetland communities, and areas with suitable soil moisture that support a complex vegetative structure with a thick cover of leaf litter or dense mats of low-lying vegetation to be the essential components of the physical and biological features essential to the conservation of the species.
Little is known about the reproductive needs of the Buena Vista Lake shrew. The breeding season begins in February or March and ends in May or June, but can be extended depending on habitat quality and available moisture (Paul Collins 2000, p. 12). The edges of wetland or marshy habitat provide the shrew with a sheltered and hospitable environment, and provide a prey base that enables the shrew to give birth and raise its young. The dense vegetative understory also provides young with cover from predators. Dense vegetation also allows for the soil moisture necessary for a consistent supply of terrestrial and aquatic insect prey (Freas 1990, p. 8; Kirkland 1991, p. 15; Maldonado 1992, p. 3; Maldonado
Preserving what little habitat remains for the Buena Vista Lake shrew is crucial to the survival of the species. There are many factors negatively impacting and restricting the shrew and its habitat, including selenium toxicity, habitat fragmentation, urban development, and the effects of climate change. The combined effects of climate change and habitat fragmentation have put immense pressure on species in highly developed areas like the San Joaquin Valley (Hannah and Lovejoy 2005, p. 4). Development has restricted the species to small islands of habitat with little to no connectivity or opportunity for expansion of its range. Climate change is a particular challenge for a variety of species because the interaction between additional stressors associated with climate change and current stressors could push species beyond their ability to survive (Lovejoy 2005, pp. 325-326), including the Buena Vista Lake shrew.
Our analyses under the Endangered Species Act include consideration of ongoing and projected changes in climate. The terms “climate” and “climate change” are defined by the Intergovernmental Panel on Climate Change (IPCC). 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 2007a, p. 78). The term “climate change” thus refers to a change in the mean or variability of one or more measures of climate (such as, temperature or precipitation) that persists for an extended period, typically decades or longer, whether the change is due to natural variability, human activity, or both (IPCC 2007a, p. 78).
Scientific measurements spanning several decades demonstrate that changes in climate are occurring, and that the rate of change has been faster since the 1950s. Examples include warming of the global climate system, and substantial increases in precipitation in some regions of the world and decreases in other regions. (For these and other examples, see IPCC 2007a, p. 30; and Solomon
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 (e.g., Meehl
Various changes in climate may have direct or indirect effects on species. These effects may be positive, neutral, or negative, and they may change over time, depending on the species and other relevant considerations, such as interactions of climate with other variables (e.g., habitat fragmentation) (IPCC 2007, pp. 8-14, 18-19). Identifying likely effects often involves aspects of climate change vulnerability analysis. Vulnerability refers to the degree to which a species (or system) is susceptible to, and unable to cope with, adverse effects of climate change, including climate variability and extremes. Vulnerability is a function of the type, magnitude, and rate of climate change and variation to which a species is exposed, its sensitivity, and its adaptive capacity (IPCC 2007a, p. 89; see also Glick
Current climate change projections for terrestrial areas in the Northern Hemisphere indicate warmer air temperatures, more intense precipitation events, and increased summer continental drying (Field
Use of downscaled climate modeling for the Sacramento-San Joaquin River Basin shows projected warming, with substantial decadal and interannual variability and altered streamflow seasonality in the southern San Joaquin Valley, suggesting that water infrastructure modifications would be needed to address changing conditions (Vanrheenen
Under the Act and its implementing regulations, we are required to identify the physical or biological features essential to the conservation of the Buena Vista Lake shrew in areas occupied at the time of listing, focusing on the features' primary constituent elements. We consider primary constituent elements to be those components 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 for the Buena Vista Lake shrew are:
Permanent and intermittent riparian or wetland communities that contain:
• A complex vegetative structure with a thick cover of leaf litter or dense mats of low-lying vegetation. Associated plant species can include, but are not limited to, Fremont cottonwoods, willows, glasswort, wild-rye grass, and rush grass. Although moist soil in areas with an overstory of willows or cottonwoods appears to be favored, such overstory may not be essential.
• Suitable moisture supplied by a shallow water table, irrigation, or proximity to permanent or semipermanent water; and
• A consistent and diverse supply of prey. Although the specific prey species utilized by the Buena Vista Lake shrew have not been identified, ornate shrews are known to eat a variety of terrestrial and aquatic invertebrates, including amphipods, slugs, and insects.
With this proposed designation of critical habitat, we intend to identify the physical or biological features essential to the conservation of the species, through the identification of the features' primary constituent elements sufficient to support the life-history processes of the species. All units and subunits proposed to be designated as critical habitat are currently occupied by the Buena Vista Lake shrew.
When designating critical habitat, we assess whether the specific areas within the geographic area occupied by the species at the time of listing contain features that are essential to the conservation of the species and that may require special management considerations or protection. The features essential to the conservation of this species may require special management considerations or protection to reduce the following threats:
All areas included in this proposed revision of critical habitat will require some level of management to address the current and future threats to the physical and biological features essential to the conservation of the Buena Vista Lake shrew. Special management considerations or protection may be required to minimize habitat destruction, degradation, or
The designated units are located in areas characterized by large-scale agricultural production, and consequently, the units may be exposed to a number of pesticides, which could detrimentally impact the species. The Buena Vista Lake shrew currently exists on small remnant patches of natural habitat in and around the margins of a landscape that is otherwise dominated by agriculture. The Buena Vista Lake shrew could be directly exposed to lethal and sublethal concentrations of pesticides from drift during spraying of crops, or potentially directly exposed during herbicide treatment of canal zones and ditch banks, wetland or riparian edges, or roadsides where shrews might exist. Reduced reproduction in Buena Vista Lake shrews could be directly caused by pesticides ingested through grooming, and secondarily from feeding on contaminated insects (Sheffield and Lochmiller 2001, p. 284). A variety of toxicants, including pesticides and heavy metals, have been shown to negatively affect insectivores, including shrews, that have a high basal metabolism and tight energy balance. Treatment-related decreases in invertebrate prey availability may be especially significant to such insectivore populations (Ma and Talmage 2001, pp. 133-152).
The Buena Vista Lake shrew also faces high risks of extinction from random catastrophic events (such as floods or drought (Service 1998, p. 163). The low numbers of Buena Vista Lake shrews located in small isolated areas increases the risk of a random catastrophic event wiping out entire populations or severely diminishing Buena Vista Lake shrew numbers beyond the scope of recovery. These threats and others mentioned above could render the habitat less suitable for the Buena Vista Lake shrew by washing away leaf litter and complex vegetation structure (floods) or drying wetland habitat so that vegetative and prey communities die (drought), and special management may be needed to address these threats.
In summary, the critical habitat units identified in this designation may require special management considerations or protection to provide a functioning hydrological regime to maintain the requisite riparian and wetland habitat, which is essential in providing the space and cover necessary to sustain the entire life-cycle needs of the shrew, as well as its invertebrate prey. Changes in water supply could result in the alteration of the moisture regime, which could lead to reduced water quality or hydroperiod, loss of suitable invertebrate supply for feeding, and loss of complex vegetative structure for cover. The units may also require special management considerations due to ongoing pressures for agricultural conversion and oil and gas exploration, and pesticide use, and vulnerabilities associated with low population size and population fragmentation.
On January 24, 2005, we designated 84 ac (34 ha) in Kern County, California, as critical habitat for the Buena Vista Lake shrew (70 FR 3438). On October 21, 2009, we published in the
As required by section 4(b)(2) of the Act, we use the best scientific data available to designate critical habitat. We review available information pertaining to the habitat requirements of the species. In accordance with the Act and its implementing regulation at 50 CFR 424.12(e), we consider whether designating additional areas—outside those currently occupied as well as those occupied at the time of listing—is necessary to ensure the conservation of the species. At the time of listing, we were aware of four locations (Kern Lake, Kern National Wildlife Refuge, Coles Levee, and the Kern Fan Water Recharge Area) where the Buena Vista Lake shrew was extant, but we also noted that additional remnant patches of wetland and riparian habitat within the Tulare Basin had not been surveyed and might support the shrew (Service 2002, p. 10103). We considered the geographical area occupied by the species to include areas of remnant wetland and riparian habitat within the Tulare Basin.
As noted previously, shrews were also known from Atwell Island, Tulare County (Williams and Harpster 2001, pp. 13, 14), but had not been identified as Buena Vista Lake shrews. In January 2003, a fifth site, Goose Lake, was surveyed and Buena Vista Lake shrews were also identified at this location (ESRP 2004, p. 8). The Goose Lake Unit was included in the original proposal to designate critical habitat (Service 2004). The Lemoore and Semitropic sites were first surveyed for the Buena Vista Lake shrew in April 2005, and Buena Vista Lake shrews were captured at these sites (ESRP 2005, p. 11, 12).
We propose to designate critical habitat in areas within the geographical area occupied by the species at the time of listing. We include as occupied those areas that meet the following two conditions: (1) They contain the physical or biological features that are essential to the conservation of the species, and (2) they wer