the greatest extinction risks from global warming may be in the tropics, where biological diversity is also greatest

Impacts of climate warming on terrestrial ectotherms across latitude

...(our)... results show that warming in the tropics, although relatively small in magnitude, is likely to have the most deleterious consequences because tropical insects are relatively sensitive to temperature change and are currently living very close to their optimal temperature.... in the absence of ameliorating factors such as migration and adaptation, the greatest extinction risks from global warming may be in the tropics, where biological diversity is also greatest.

http://www.pnas.org/cgi/reprint/0709472105v1