Las Cruces, NM, United States
Las Cruces, NM, United States

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Calkins M.T.,Center for Applied Spatial Ecology | Beever E.A.,3115 Briarcliff Dr. | Beever E.A.,U.S. Geological Survey | Boykin K.G.,Center for Applied Spatial Ecology | And 2 more authors.
Ecography | Year: 2012

We modeled current and future distribution of suitable habitat for the talus-obligate montane mammal Ochotona princeps (American pika) across the western USA under increases in temperature associated with contemporary climate change, to: a) compare forecasts using only climate variables vs using those plus habitat considerations; b) identify possible patterns of range collapse (center vs margins, and large- vs small-sized patches); and c) compare conservation and management implications of changes at two taxonomic resolutions, and using binned- vs binary-probability maps. We used MaxEnt to analyze relationships between occurrence records and climatic variables to develop a bioclimatic-envelope model, which we refined by masking with a deductive appropriate-habitat filter based on suitable land-cover types. We used this final species-distribution model to predict distribution of suitable habitat under range-wide temperature increases from 1 to 7°C, in 1°C increments; we also compared these results to distribution under IPCC-forecasted climates for 2050 and 2080. Though all currently recognized lineages and traditionally defined subspecies were predicted to lose increasing amounts of habitat as temperatures rose, the most-dramatic range losses were predicted to occur among traditional subspecies. Nineteen of the 31 traditional US pika subspecies were predicted to lose > 98% of their suitable habitat under a 7°C increase in the mean temperature of the warmest quarter of the year, and lineages were predicted to lose 88 95% of suitable habitat. Under a 4°C increase, traditional subspecies averaged a predicted 73% (range = 44-99%) reduction. The appropriate-habitat filter removed 40-6% of the predicted climatically suitable pixels, in a stepped and monotonically decreasing fashion as predicted temperatures rose. Predicted range collapse proceeded until only populations in island-biogeographic 'mainlands' remained, which were not in the geographic range center. We used this model system to illustrate possible distributional shifts under stepped changes in biologically relevant aspects of climate, importance of land cover and taxonomic level in species-distribution forecasts, and impact of using a single threshold vs multiple categories of persistence probability in predicted range maps; we encourage additional research to further investigate the generality of these patterns. © 2012 The Authors. Ecography © 2012 Nordic Society Oikos.


Villarreal M.L.,U.S. Geological Survey | Norman L.M.,U.S. Geological Survey | Boykin K.G.,Center for Applied Spatial Ecology | Wallace C.S.A.,U.S. Geological Survey
International Journal of Biodiversity Science, Ecosystems Services and Management | Year: 2013

The Sonoran Desert and Apache Highlands ecoregions of North America are areas of exceptionally high plant and vertebrate biodiversity. However, much of the vertebrate biodiversity is supported by only a few vegetation types with limited distributions, some of which are increasingly threatened by changing land uses. We assessed the impacts of two future urban growth scenarios on biodiversity in a binational watershed in Arizona, USA and Sonora, Mexico. We quantified and mapped terrestrial vertebrate species richness using Wildlife Habitat Relation models and validated the results with data from National Park Service (NPS) biological inventories. Future urban growth, based on historical trends, was projected to the year 2050 for (1) a Current Trends (CT) scenario and (2) a Megalopolis (MEGA) scenario that represented a transnational growth corridor with open-space conservation attributes. Based on CT, 45% of existing riparian woodland (267 of 451species) and 34% of semi-desert grasslands (215 of 451 species) will be lost, whereas in the MEGA scenario, these types would decline by 44% and 24%, respectively. Outcomes of the two models suggest a trade-off at the taxonomic class level: CT would reduce and fragment mammal and herpetofauna habitat, while MEGA would result in loss of avian-rich riparian habitat. © 2013 Copyright This work was authored as part of the Contributors official duties as Employees of the United States Government and is therefore a work of the United States Government. In accordance with 17 USC. 105, no copyright protection is available for such works under US Law.

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