A Climate Change Vulnerability Assessment of California's At-Risk Birds

Abstract

Conservationists must develop new strategies and adapt existing tools to address the consequences of anthropogenic climate change. To support statewide climate change adaptation, we developed a framework for assessing climate change vulnerability of California's at-risk birds and integrating it into the existing California Bird Species of Special Concern list. We defined climate vulnerability as the amount of evidence that climate change will negatively impact a population. We quantified climate vulnerability by scoring sensitivity (intrinsic characteristics of an organism that make it vulnerable) and exposure (the magnitude of climate change expected) for each taxon. Using the combined sensitivity and exposure scores as an index, we ranked 358 avian taxa, and classified 128 as vulnerable to climate change. Birds associated with wetlands had the largest representation on the list relative to other habitat groups. Of the 29 state or federally listed taxa, 21 were also classified as climate vulnerable, further raising their conservation concern. Integrating climate vulnerability and California's Bird Species of Special Concern list resulted in the addition of five taxa and an increase in priority rank for ten. Our process illustrates a simple, immediate action that can be taken to inform climate change adaptation strategies for wildlife.

Vulnerability of birds to climate change in California's Sierra Nevada

“…The most important source of differences between our results and those of Gardali et al (2012) is likely the spatial scales under consideration, i.e., the entire state of California by Gardali et al (2012) and the Sierra Nevada in our analysis. Our study, like that of Gardali et al, evaluated vulnerability in a spatially explicit context; for species with broader distributions in California than just the Sierra Nevada, projected climate change exposure may vary substantially across the two areas of inference.…”

“…Because the climate models we used are considered likely to bracket future conditions, we consider our vulnerability rankings to be relatively robust to uncertainties in the climate projections. Gardali et al (2012) recently used fairly similar methods to assess climate change vulnerability for selected bird species across California as a whole. However, their analysis included many species associated with marine, desert, and other habitats not present in the Sierra Nevada, and subject to threats, e.g., sea level rise, that are not relevant to the Sierra Nevada region.…”

“…Gardali et al (2012) evaluated 14 of the 17 species that ranked as Moderately Vulnerable or Extremely Vulnerable in our analysis, and considered 6 of them to be climate-vulnerable across California as a whole: Osprey, Great Gray Owl, Black Swift (Cypseloides niger), Swainson's Thrush, Gray-crowned Rosy-Finch, and Pine Grosbeak (Pinicola enucleator). Two more of the 17 species, Peregrine Falcon (Falco peregrinus) and American Dipper, received vulnerability scores only slightly below the cutoff that Gardali et al (2012) used to separate taxa into vulnerable versus nonvulnerable.…”

“…Additionally, other nonclimate factors, such as habitat destruction and urban encroachment, or small population size, could also be important in driving overall vulnerability. Our results therefore will need to be considered in concert with other nonclimate factors for establishing conservation priorities and formulating management strategies (Ohlemüller et al 2008, Young et al 2011, Gardali et al 2012, Anacker et al 2013). …”

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“…Similarly, the perceived vulnerability of these species to a changing climate (e.g., Gardali et al 2012) illustrates the need to develop a better understanding of how climatic conditions influence their distribution and abundance.…”