The Geckos of Pemba Island, Tanzania

According to authors Rodder et al. (2010), "if the climate changes, island endemics may be restricted in their ability to conduct range shifts depending on the topographic variability and the size of the island," and they say that "species that inhabit islands characterized by low altitudinal variation may be the ones most strongly affected by climate change due to the lack of possibilities for horizontal or upward range shifts." However, they note that only a small part of the fundamental niche of a species may currently be available to it, and that the species may possess a hitherto unknown ability to tolerate a much greater range of environmental conditions than that to which it may have been exposed in the recent past. Therefore, in determining what climatic conditions a species may be able to tolerate in the future, they state that "a comparison between conditions tolerated in the present and in the past may be helpful."

Focusing on Phelsuma parkeri, an endemic gecko species native to the relatively flat (0 to < 100 m elevation) island of Pemba, Tanzania, Rodder et al. employed this approach by observing the species and providing information on its current spatial distribution in terms of both physical and environmental space, as well as its adaptability to habitat modification by humans. With respect to past climatic conditions, they employed simulations of the Last Glacial Maximum provided by the Community Climate System Model and the Model for Interdisciplinary Research on Climate, while with respect to the future, they employed climate change predictions based on three other models and the emission scenarios reported in the Special Report on Emissions Scenarios by the Intergovernmental Panel on Climate Change.

The three researchers report that a comparison of current climatic conditions with those derived from model simulations for 21,000 years ago revealed that "no climate conditions analogous to those of today existed during the Last Glacial Maximum," noting that there were "decreases of between 1.4 and 2.8°C in the minimum temperature of the coldest month and of between 2.1 and 3.4°C in the maximum temperature of the warmest month throughout the island" compared to the corresponding temperatures of today. As for the future, the climate models they used suggested that "the minimum temperature of the coldest month may increase about 1.2 to 3.8°C and the maximum temperature of the warmest month by about 2.0 to 3.7°C."

In considering these findings, Rodder et al. say their results suggest that "P. parkeri is distributed over the largest part of the island, that it is well adapted to current land use, and that it is most likely not threatened by climate change."