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Predicting Species Extinctions in Response to Global Warming
Dormann, C.F. 2007. Promising the future? Global change projections of species distributions. Basic and Applied Ecology 8: 387-397.

Thomas et al. (2004) suggested that ecosystem biodiversity will decline, and many endangered plant species will disappear altogether, as a result of continued unprecedented increases in air temperature, calculating that 15-37% of the species of plants scattered throughout many regions of the earth will be "committed to extinction" by the year 2050. For two opposing points of view, however, see our Editorials of 14 January 2004 and 12 May 2004.

What was done
In light of the great publicity and discussion generated by Thomas et al.'s paper, the author felt it important to "review the main shortcomings of species distribution models and species distribution projections," such as those employed (the models) and derived (the projections) by Thomas et al., and in doing so, he analyzed three aspects of what he calls "problems associated with species distribution models." The first of these aspects is general species distribution model issues, under which he lists four major problems. The second is extrapolation issues, under which he lists five major problems; and the third is statistical issues, under which he lists six major problems.

What was learned
When all was said and done, Dormann concluded that "the problems associated with the analysis of [the] present distribution[s] of species are so numerous and fundamental that common ecological sense should caution us against putting much faith in relying on their findings for further extrapolations," in contrast to what is routinely done in studies such as that of Thomas et al., the latter of whose methods and findings, according to Dormann, "have been challenged for conceptual and statistical reasons" by many other researchers.

What it means
Dormann notes that "projections of species distributions are not merely generating hypotheses to be tested by later data," as is typical of the scientific enterprise. Instead, as he correctly indicates, "they are presented as predictions of tomorrow's diversity, and policy makers and the public will interpret them as forecasts, similar to forecasts about tomorrow's weather," which he clearly feels is both unwarranted and unwise.

Thomas, C.D., Cameron, A., Green, R.E., Bakkenes, M., Beaumont, L.J., Collingham, Y.C., Barend, F., Erasmus, N., Ferreira de Siqueira, M., Grainger, A., Hannah, L., Hughes, L., Huntley, B., van Jaarsveld, A.S., Midgley, G.F., Miles, L., Ortega-Huerta, M.A., Peterson, A.T., Phillips, O.L. and Williams, S.E. 2004. Extinction risk from climate change. Nature 427: 145-148.

Reviewed 6 February 2008