The study by Deutsch et al. examines the impacts of climate warming on terrestrial ectotherms, focusing on the latitudinal variation in these effects. The authors integrate empirical fitness curves of thermal tolerance for insects from around the world with projected climate change distributions to estimate the direct impact of warming on insect fitness. They find that while warming in the tropics is relatively small, it is likely to have the most detrimental consequences because tropical insects are highly sensitive to temperature changes and are already living close to their optimal temperatures. In contrast, species at higher latitudes have broader thermal tolerances and are currently living in cooler climates, so warming may even enhance their fitness. Similar patterns are observed in several vertebrate taxa, suggesting that these results are general for terrestrial ectotherms. The authors conclude that, without mitigating factors like migration and adaptation, the greatest extinction risks from global warming may be in the tropics, where biological diversity is also highest.The study by Deutsch et al. examines the impacts of climate warming on terrestrial ectotherms, focusing on the latitudinal variation in these effects. The authors integrate empirical fitness curves of thermal tolerance for insects from around the world with projected climate change distributions to estimate the direct impact of warming on insect fitness. They find that while warming in the tropics is relatively small, it is likely to have the most detrimental consequences because tropical insects are highly sensitive to temperature changes and are already living close to their optimal temperatures. In contrast, species at higher latitudes have broader thermal tolerances and are currently living in cooler climates, so warming may even enhance their fitness. Similar patterns are observed in several vertebrate taxa, suggesting that these results are general for terrestrial ectotherms. The authors conclude that, without mitigating factors like migration and adaptation, the greatest extinction risks from global warming may be in the tropics, where biological diversity is also highest.