Projected Climate Effects on Birds and Reptiles of the Southwestern United States
Summary
Global circulation models (GCM) of future climates predict extreme change for the Southwestern United States (Solomon and others, 2007; Diffenbaugh and others, 2008). Temperatures are projected to increase 3.5–4°C within the next 60–90 years while precipitation is projected to decline by 5–20 percent (Seager and others, 2007). The coalescing effect of these changes in temperature and precipitation in this already arid region will profoundly affect the distributions and viability of plant and animal populations. Region-wide ecosystem processes and system dynamics will be especially sensitive to relatively small shifts in climate in the arid and semi-arid environments (Millennium Ecosystem Assessment, 2005). Managers of public lands [...]
Summary
Global circulation models (GCM) of future climates predict extreme change for the Southwestern United States (Solomon and others, 2007; Diffenbaugh and others, 2008). Temperatures are projected to increase 3.5–4°C within the next 60–90 years while precipitation is projected to decline by 5–20 percent (Seager and others, 2007). The coalescing effect of these changes in temperature and precipitation in this already arid region will profoundly affect the distributions and viability of plant and animal populations. Region-wide ecosystem processes and system dynamics will be especially sensitive to relatively small shifts in climate in the arid and semi-arid environments (Millennium Ecosystem Assessment, 2005).
Managers of public lands and associated wildlife resources in the Southwestern United States need information about climate change consequences so they can better adapt management strategies to help conserve and sustain habitats of wildlife species. Prediction of coarse-scale changes, such as shifts in the distribution of dominant plant species, are needed to identify those habitats most vulnerable to climate change and to aid in prioritizing conservation efforts (U.S. Fish and Wildlife Service, 2010; Rowland and others, 2011). Dominant vegetation structure is a major
determinant of the distribution of many animal species. Probabilistic predictions of future wildlife species distributions, directly linked to climate change, are needed to provide managers with empirical assessments of the future prospects for all species and especially those of special interest.
We report here on a project that utilized downscaled climate projections for the A1B emission scenario (a balanced emphasis on all energy sources in the next century) to project potential changes in birds and reptile ranges throughout the Southwestern United States. We used species distribution models (also referred to as ecological niche, bioclimatic, or habitat distribution models) to estimate losses and gains in projected ranges of select upland species in response to projected climate change. Following the admonitions and advice of previous researchers (for
example, Luoto and Heikkinen, 2008; Thuiller and others, 2008; Virkkala and others, 2010; McMahon and others, 2011), we included the cascading effects of static landscape features and changing plant species distributions to assess the potential dynamics of habitat change, including
thresholds and tipping points.
Our study area focused on the Sonoran Desert and Colorado Plateau ecosystems within Arizona, western New Mexico, Utah, southwestern Colorado, and southeastern California, but also included the rest of the Western United States. Focal wildlife species included resident and migratory birds and reptiles, which compose the majority of vertebrate biodiversity in this region (Boykin and others, 2007). Focal species were selected based on several sources of information, including input from a Resource Managers Advisory Group as well as wildlife and conservation partners. To assure relevance and responsiveness to real world management needs, we established an advisory team to provide guidance and feedback on all aspects of the project including planning, species prioritization, data acquisition and management, and product delivery tools.
