The Earth is experiencing historically unprecedented rates of warming, with surface temperatures projected to increase by 3-5°C globally, and up to 7.5°C in high latitudes, within the next century.  Additional stressors are associated with global warming in fresh waters, including an increase in the intensity and duration of droughts.  Knowledge of how these changes will affect biological systems is still largely restricted to the lower levels of organisation (e.g. species range shifts), rather than at the community, food web or ecosystem level, where responses cannot be predicted from studying single species in isolation.  We present data from a range of systems and levels of organisation to explore the likely consequences of climate change and global warming in the northern hemisphere.  Our approach combines survey data from a “natural experiment” and field manipulations in Iceland and the U.K., with more focused laboratory trials using microcosms. 

Results/Conclusions

Among the biological responses we have observed are: a simplification of food web structure and reduced biomass production during droughts; increases in food web height and chain length across a thermal gradient; alterations in the metabolic balance of whole ecosystems due to warming.  These findings provide valuable new insights into how the more complex levels of the biological hierarchy (communities, food webs, ecosystems) might respond in future scenarios predicted within the next 100 years of global change.