A Framework for Categorizing the Relative Vulnerability of Threatened and Endangered Species to Climate Change (External Review Draft)

This report describes an evaluative framework that may be used to categorize the relative vulnerability of species to climate change. Four modules compose this framework: Module 1 categorizes baseline vulnerability to extinction or major population reduction by scoring those elements of the species’ life history, demographics, and conservation status that influence the likelihood of its survival or extinction (excluding climatic changes); Module 2 scores the likely vulnerability of a species to future climate change, including the species’ potential physiological, behavioral, demographic, and ecological response to climate change; Module 3 combines the results of Modules 1 and 2 into a matrix to produce an overall score of the species’ vulnerability to climate change, which maps to an adjectival category, such as “critically vulnerable”, “highly vulnerable”, “less vulnerable”, and “least vulnerable”; Module 4 is a qualitative determination of uncertainty of overall vulnerability (high, medium, and low) based on evaluations of uncertainty done in each of the first 3 modules. To illustrate the use of this framework, it was applied to five U.S. threatened and endangered species and one species that has since been delisted. Based on the authors’ evaluation, four of those species were categorized as “critically vulnerable”: the golden-cheeked warbler (Dendroica chrysoparia), the salt marsh harvest mouse (Reithrodontomys raviventris), the Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis), and the Lahontan cutthroat trout (Oncorhyncus clarki henshawi). The desert tortoise (Gopherus agassizii) was characterized as “highly vulnerable” and the bald eagle (Haliaeetus leucocephalus) -- now delisted, except for the southwest population -- was categorized as “less vulnerable”. Certainty scores in Module 4 ranged between medium and high and reflect the amount and quality of information available.