Ecology

A Climate for Extinction

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Science  10 May 2002:
Vol. 296, Issue 5570, pp. 983
DOI: 10.1126/science.296.5570.983a

Throughout evolutionary history, climate change has been an important force in the evolution and extinction of populations and species. Extinction may occur through failure to adapt to new conditions or through an inability to track geographical shifts in hospitable regions. Anthropogenic climate change is expected to exacerbate the current global extinction crisis.

Now McLaughlin et al. have provided an early indication of an extinction caused by contemporary climate change. Over a 40-year study period, two populations of checkerspot butterflies in the San Francisco Bay Area, California, gradually declined to extinction as the annual variability in rainfall became more unpredictable. A population-modeling exercise showed that precipitation variability led to increased population fluctuations in the butterfly, which increased the likelihood of extinction when population size dipped below a critical level. Climate models indicate that increased variability is an expected component of human-induced climate change. The fate of the checkerspot might therefore portend similar extinctions in the future.—AMS

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.052131199 (2002).

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