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How Does Climate Change Affect the Ranges of European Birds?
Beale, C.M., Lennon, J.J. and Gimona, A. 2008. Opening the climate envelope reveals no macroscale associations with climate in European birds. Proceedings of the National Academy of Sciences USA 105: 14,908-14,912.

Climate envelopes, in the words of the authors, "are the current methods of choice for prediction of species distributions under climate change and their use is growing rapidly in many areas of ecology." However, they note "there are many reasons why species distributions may not match climate, including biotic interactions, adaptive evolution, dispersal limitation, and historical chance."

What was done
To better assess this situation, Beale et al. quantified "the match of species distributions to environment" by generating 99 synthetic species distributions for each of 100 species of birds (based on data taken from the European Breeding Bird Atlas) that retained "the spatial structure in the observed distributions but were randomly placed with respect to climate," after which they "fitted climate envelope models to both the true distribution and the 99 simulated distributions by using standard climate variables," evaluating the results via a number of statistical tests.

What was learned
As described by the three researchers, they determined that "species-climate associations found by climate envelope methods are no better than chance for 68 of 100 European bird species," which finding led them to state that "the distributions of most birds in our study are not strongly associated with the climate variables currently available."

What it means
Beale et al. "therefore conclude," as they put it, "that many, if not most, published climate envelopes may be no better than expected from chance associations alone, questioning the implications of many published studies." As a result, they also conclude that the climate envelope model "is certainly not a model that should inform policy," especially, we might add, as used by Al Gore and James Hansen.

Reviewed 3 December 2008