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Birds and Climate
Reference
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.

Background
The authors write that "climate envelopes (or the climatic niche concept) 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 report that "climate envelope methods and assumptions have been criticized as ecologically and statistically na´ve (Pearson and Dawson, 2003; Hampe, 2004)," and that "there are many reasons why species distributions may not match climate, including biotic interactions (Davis et al., 1998), adaptive evolution (Thomas et al., 2001), dispersal limitation (Svenning and Skov, 2007), and historical chance (Cotgreave and Harvey, 1994)."

What was done
In an attempt to shed more light on the subject, Beale et al. evaluated the degree of matchup of species distributions to environment by generating synthetic distributions that retained the spatial structure of observed distributions but were randomly placed with respect to climate. More specifically, "using data on the European distribution of 100 bird species, [they] generated 99 synthetic distribution patterns for each species," and "for each of the 100 species, [they] fitted climate envelope models to both the true distribution and the 99 simulated distributions by using standard climate variables," after which they determined the goodness-of-fit of the many distribution patterns, because, as they describe it, "there has been no attempt to quantify how often high goodness-of-fit scores, and hence ostensibly good matches between distribution and climate, can occur by chance alone."

What was learned
In a rather surprising result, the three UK researchers determined that "species-climate associations found by climate envelope methods are no better than chance for 68 of 100 European bird species."

What it means
Beale et al. say that "because birds are perceived to be equally strongly associated with climate as other species groups and trophic levels (Huntley et al., 2004)," their results "cast doubt on the predictions of climate envelope models for all taxa." Hence, they conclude 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." The bottom line with respect to our stewardship of the earth is thus well described by their conclusion that "scientific studies and climate change adaptation policies based on the indiscriminate use of climate envelope methods irrespective of species sensitivity to climate may be misleading and in need of revision."

References
Cotgreave, P. and Harvey, P.H. 1994. Associations among biogeography, phylogeny and bird species diversity. Biodiversity Letters 2: 46-55.

Davis, A.J., Jenkinson, I.S., Lawton, J.H., Shorrocks, B. and Wood, S. 1998. Making mistakes when predicting shifts in species range in response to global warming. Nature 391: 783-786.

Hampe, A. 2004. Bioclimate envelope models: what they detect and what they hide. Global Ecology and Biogeography 13: 469-471.

Huntley, B., Green, R.E., Collingham, Y.C., Hill, J.K., Willis, S.G., Bartlein, P.J., Cramer, W., Hagemeijer, W.J.M. and Thomas, C.J. 2004. The performance of models relating species geographical distributions to climate is independent of trophic level. Ecology Letters 7: 417-426.

Pearson, R.G. and Dawson, T.P. 2003. Predicting the impacts of climate change on the distribution of species: Are bioclimate envelope models useful? Global Ecology and Biogeography 12: 361-371.

Svenning, J.C. and Skov, F. 2007. Could the tree diversity pattern in Europe be generated by postglacial dispersal limitation? Ecology Letters 10: 453-460.

Thomas, C.D., Bodsworth, E.J., Wilson, R.J., Simmons, A.D., Davies, Z.G., Musche, M. and Conradt, L. 2001. Ecological and evolutionary processes at expanding range margins. Nature 411: 577-581.

Reviewed 4 March 2009