Nonlinear Responses of Lake Ecosystems to Climate Change

A growing literature suggests that ecosystems in the tropics may be more sensitive to the impacts of climate change than those at higher latitudes. We add to that growing literature by showing that the responses of lake ecosystems to warming can be greater in the tropics even when warming rates are relatively small compared to higher latitudes. This pattern can be explained by nonlinear ecosystem responses to temperature. For example, due to nonlinear responses of the carbon cycle to temperature, increasing temperatures can have disproportionately large impacts on primary production, methane efflux, and organism metabolism in the tropics where baseline temperatures are already relatively high. We compile long-term temperature records (40+ years) from more than 20 tropical, temperate, and arctic lakes spanning a latitudinal range from 60 degrees south latitude to 60 degrees north latitude. We use well-established relationships between temperature and carbon cycling rates to model the impact of warming on primary production, ecosystem respiration, and methane efflux rates in each of our 20 focal lakes. Our results demonstrate that climate change exerts a powerful force on freshwater ecosystems worldwide, but while warming rates may be higher at higher latitude, ecosystem impacts on lakes may be disproportionate to warming rates