Renewable Energy and Xerospermophilus Mohavensis
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Vol. 20: 1–18, 2013 ENDANGERED SPECIES RESEARCH Published online February 22 doi: 10.3354/esr00487 Endang Species Res OPENPEN ACCESSCCESS FEATURE ARTICLE Is there room for all of us? Renewable energy and Xerospermophilus mohavensis Richard D. Inman1, Todd C. Esque1,*, Kenneth E. Nussear1, Philip Leitner2, Marjorie D. Matocq3, Peter J. Weisberg3, Tomas E. Dilts3, Amy G. Vandergast4 1U.S. Geological Survey, Western Ecological Research Center, United States Geologic Survey, Las Vegas Field Station, Henderson, Nevada 89074-8829, USA 2California State University Stanislaus, Endangered Species Recovery Program, One University Circle, Turlock, California 95382, USA 3University of Nevada, Reno, Department of Natural Resources and Environmental Science, Program in Ecology, Evolution and Conservation Biology, Reno, Nevada 89557, USA 4U.S. Geological Survey, Western Ecological Research Center, San Diego Field Station, San Diego, California 92101, USA ABSTRACT: Mohave ground squirrels Xerosper- mophilus mohavensis Merriam are small ground- dwelling rodents that have a highly restricted range in the northwest Mojave Desert, California, USA. Their small natural range is further reduced by habitat loss from agriculture, urban develop- ment, military training and recreational activities. Development of wind and solar resources for re - newable energy has the potential to further re - duce existing habitat. We used maximum entropy habitat models with observation data to describe current potential habitat in the context of future renewable energy development in the region. Xerospermophilus mohavensis, wind turbines, and predicted While 16% of historic habitat has been impacted habitat suitability (in the Mojave Desert, California, USA) by, or lost to, urbanization at present, an additional ranging from low (blue) to high (red). 10% may be affected by renewable energy devel- Image: M. A. Walden opment in the near future. Our models show that X. moha vensis habitat suitability is higher in areas slated for renewable energy development than in INTRODUCTION surrounding areas. We provide habitat maps that can be used to develop sampling designs, evaluate In recent decades the desert southwest region, conservation corridors and inform development planning in the region. including the Mojave Desert, has seen some of the highest population growth in the USA, resulting in KEY WORDS: Mohave ground squirrel · large-scale landscape modification and loss of habi- Renewable energy · Habitat suitability · Maximum tat (Leu et al. 2008). Habitat loss and modification entropy due to urban development, utility infrastructure, transportation corridors, military training and recre- Resale or republication not permitted without written consent of the publisher ational activities are occurring at an accelerating *Corresponding author. Email: [email protected] © Inter-Research 2013 · www.int-res.com 2 Endang Species Res 20: 1–18, 2013 pace throughout the region (Lovich & Bainbridge ment of Fish and Game 2011). While habitat loss has 1999, Webb et al. 2009). Now the southwestern been identified as the greatest peril for MGS deserts are recognized as having great potential for (Fish and Wildlife Service 2011; see also Defenders renewable energy development given the availabil- of Wildlife & G. Stewart at www. defenders. org/ ity of public land and abundant wind, solar and geot- newsroom/ press_ releases_ folder/2005/ 09_ 13_ 2005 _ hermal resources (NREL 2012). In recent years, pub- protection_ sought_ for_ mohave_ desert_ ground_ squirrel lic policy initiatives at both federal and state levels .php), a comprehensive, range-wide assessment of (e.g. the American Recovery and Reinvestment Act habitat has not yet been published. Previous efforts of 2009, CA Executive Order S-14-08 and CA Senate to describe habitat have been qualitative, resulting in Bill X1-2, among others) have mandated or encour- descriptions of habitat characteristics and multiple aged the development of renewable energy. modifications to range maps (Zembal & Gall 1980, One of the major benefits of increasing renewable Hall 1981, Zeiner et al. 1988−1990). While these energy generation includes reducing greenhouse gas range maps provide useful information on the known emissions (thus mitigating global climate change), in- extent of a species, they do not delineate areas of creasing national energy security and supporting eco- habitat and non-habitat within their extant range, nomic growth. The potential for renewable energy in which can be problematic when used for assessing the desert means that public lands in this region are areas of high biodiversity for conservation purposes now in great demand for development. However, the (Pineda & Lobo 2012). prospect of large-scale energy development and its Conservation planning for many species has been associated infrastructure has raised serious concerns facilitated by the use of species distribution models regarding impacts on desert biological resources, in- (SDMs) for tasks such as the design of conservation cluding many sensitive or protected species such as and monitoring programs, evaluating the efficacy or the desert tortoise Gopherus agassizii (Fish and Wild - potential effects of management actions, and recov- life Service 1990), the desert bighorn sheep Ovis ery planning (Graham et al. 2004, Elith & Leathwick canadensis nelsoni (Fish and Wildlife Service 1998) 2009a, Fish and Wildlife Service 2011). These SDMs, and Stephens’ kangaroo rat Dipo do mys stephensi or habitat suitability models, are quantitative, spa- (Fish and Wildlife Service 1988), among others. tially explicit models that relate species occurrence The Mohave ground squirrel (MGS; Xerosper- to environmental predictors thought to influence or mophilus mohavensis Merriam) could also be affected define the suitability of habitat for the species by the development of renewable energy resources. (Franklin 2010, Peterson et al. 2011). These models The species is endemic to the western Mojave Desert can be ecologically complex or very simple, and can in California, USA, and occupies portions of Kern, Los be modeled at many scales. Habitat models are fre- Angeles, Inyo and San Bernardino counties (Best quently built with presence-only data (as absence 1995). The geographic range is thought to be approxi- data for most species are often unavailable), and pro- mately 20 000 km2 (Hall 1981, Zeiner et al. 1988− vide a relative index of habitat suitability that can be 1990), one of the smallest distributions among North predicted on a landscape scale. American ground squirrels (Hoyt 1972, P. Leitner pers. Because SDMs have not yet been published for the obs.). MGS occupy a harsh desert environment, and MGS, conservation and planning decisions have been adult individuals are primarily active during a brief made entirely on previously published range maps. period from February to the end of July (Best 1995). In 2011, a petition for federal listing of the species The restricted distribution of MGS, along with the (www. defenders. org/ newsroom/ press_releases_ folder/ extensive impacts of human development in the 2005/ 09_ 13_ 2005 _ protection_ sought_ for_ mohave _ western Mojave Desert, has contributed to concern desert_ ground_ squirrel .php) was deemed not war- about conservation of this species (Leitner 2008). In ranted by the US Fish and Wildlife Service on the particular, direct losses such as road and construction basis of 5 factors (Fish and Wildlife Service 2011). mortalities (Gustafson 1993) and the cumulative One of these factors included ‘the present or threat- impacts (sensu Theobald et al. 1997) of landscape- ened destruction, modification, or curtailment of its level disturbances (e.g. off-highway vehicles use, habitat or range’, and in their ruling, the Fish and agriculture, military operations) could further reduce Wildlife Service provided estimates of minimal habi- population numbers of MGS and connectivity of suit- tat loss due to land-use activities including urbaniza- able habitat patches. In response to these concerns, tion, agriculture and re new able energy. These esti- MGS was listed as threatened under the California mates were based on range maps that were the best Endangered Species Act in 1984 (California Depart- available information for planning purposes in lieu of Inman et al.: Renewable energy and habitat for Mohave ground squirrels 3 SDMs. However, a larger percentage of habitat has trapping and survey work (P. Leitner & D. Delaney likely been lost in recent history than has been previ- unpubl. data). Due to the low density of sampling and ously reported. biased geographic distribution of observations, we Conflicts between interests for large-scale renew- included records dating back to 1975 to increase able energy development in the western Mojave sample size. Records with known spatial uncertainty Desert and conservation of MGS habitat have delayed greater than 1 km (33 records) were excluded to the establishment of energy facilities, and heightened keep the spatial precision of MGS observations simi- the potential for costly litigation. Analyses on the ex- lar to that of the environmental data layers, and the tent to which habitat may or may not be affected by desired resolution of the habitat model (i.e. 1 km2). proposed utility-scale renewable energy development We limited observations to 1 per 1 km2 grid cell, and (USRED) are critically needed to reduce conflict be- incorporated a bias file to reduce the influence of tween these competing interests,