How Does Climate Change Cause Extinction?

One concern related to the consequences of anthropogenic climate change is the extinction of vulnerable species. While climate change has been predicted to affect the populations of these species, few studies have concretely identified the precise mechanisms through which populations will be affected. Using population studies and the empirical support for climate related extinctions, Cahill et al. (2013) reviewed the many different avenues through which extinction may occur as a result of climate change. By examining both the direct and proximate factors causing extinction, this review outlines each possible cause and presents any known empirical support for each cause. Cahill et al. additionally provides instruction on mechanisms for finding proximate causes for extinction. The reviewed data highlight that changes in species interactions are the important proximate cause of extinction relating to global climate change and that further studies will be crucial for developing effective conservation strategies. –Lizzie Medford

Cahill, A., Aiello-Lammens, M., Fisher-Reid, M., 2013. How does climate change cause extinction? Proceedings of 
The Royal Society Proc R Soc B 280: 20121890

                  Many different causes for extinction relating to changes in the earth’s climate have been proposed, however few have ample empirical evidence due to the complex nature of population dynamics and species interactions. In the past, these proximate causes have included negative impact of heat-avoidance behavior, loss of host and pollinator species, increased pathogen and competitor populations, among others. In their review, Cahill et al.grouped proximate causes into different categories helping to evaluate the validity of each. Categories included, temperature, precipitation, temporal mismatch between species, negative impacts on beneficial species, and positive impacts on harmful species. Once the causes were clearly stated and organized, they could be properly evaluated on scientific validity as causes. The clearest change in species behavior resulting from climate change is a pattern of range shifts documented in hundreds of species. The patterns of warm-edge contraction specifically provide evidence that local extinctions have already occurred as a result of climate change. The online supplementary material for this review includes an extensive list of studies on extinctions occurring in the recent past. Of these 864 global species extinctions, only 20 are considered by the International Union for Conservation of Nature (IUCN) to have resulted from climate change and all thoroughly related to climate. Specifically, Cahill et al. referenced coral bleaching and chytrid fungus in amphibians as two examples of climate related extinctions. Of these 20 extinctions, seven were amphibian species, four were snails, two fish species, six bird species, and one rodent. Interestingly, none of these twenty became extinct as a result of limited tolerances to high temperatures.

The authors found that climate change will cause extinctions mostly by changing the way species interact with each other, which will affect food availability and breeding patterns. Surprisingly, species’ ability to adjust to higher body temperatures has not been the prominent proximal cause of global extinction. This review urges for further studies on the effects of climate change on species interaction and extinctions in general. Biophysical modeling and population range surveys are the two methods suggested by Cahill et al. for increasing the amount of data on populations that may be affected by the negative results of climate change. These additional studies would to help improve the effectiveness of conservation strategies, which will undoubtedly become more critical as climate change progresses and the number of related extinctions continues to rise.

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