by Jon Bielby
H. Arnfield, R. Grant, C. Monk & T. Uller, 2012, J. Zoology, published online in Early View (DOI: 10.1111/j.1469-7998.2012.00933.x)
The potential impacts of climate change now receive a considerable amount of coverage within scientific research. In addition to high-profile changes such as retreating polar ice-caps, changes to the phenology of species and ecosystems closer to home may also have negative impacts on biodiversity.
In particular, taxonomic groups such as amphibians, which are ectothermic and thought to be heavily reliant for the environment for their seasonal behavioural patterns, have been touted as being especially vulnerable to the effects of future changes to temperature and rainfall patterns as a result of their biology.
This study looks to investigate which climatic factors affect the timing of migration to breeding ponds to a widespread amphibian, the common toad, Bufo bufo. Using a sample of 25 sites over a ten year period, the authors found that toads tended to arrive at breeding sites earlier when temperatures were higher, but that the temperature earlier in the year did not affect arrival time, and that, overall, there has been a move towards later timing of breeding within the past 12 years, a result that contrasts with most other studies of amphibian breeding phenology.
Aside from the interest this paper has for those of us (myself included) who are interested in the behaviour and conservation of amphibians there are some broader-scale implications of this study, for example, that predicting how, where and when species may be affected by changes to the environment is really, really difficult. The precise responses that we observe and how they are affected by changes in the environment may vary according to the precise types of behaviour we choose measure as outcomes, the ecological make-up of the system in question, and the evolutionary history of the population upon which the study is based. Making broad statements about how amphibians or, for that matter, any taxonomic group are affected by climate change may therefore be extrapolations based on a relatively small number of studies, a fact that we would do well to remember. In particular, studies such as this one should serve as a nice reminder that sometimes we don’t know as much as we think we know and to highlight the importance of fine-scale studies to understand the complex biology of global change and its impacts on the ecosystems of our planet.