Risk of severe climate change impact on the terrestrial biosphere

The functioning of many ecosystems and their associated resilience could become severely compromised by climate change over the 21st century. We present a global risk analysis of terrestrial ecosystem changes based on an aggregate metric of changes in macroscopic ecosystem features including vegetation structure well as carbon and water fluxes and stores. We apply this metric to global simulations with a dynamic global vegetation model (LPJmL) under 58 WCRP CMIP3 climate change projections. Given the current knowledge of processes and projected climate change patterns, we find that severe changes cannot be excluded on any continent. They are likely to occur (in > 90% the climate projections) in the boreal–temperate ecotone where heat and drought stress might to large-scale forest die-back, along boreal and mountainous tree lines where the temperature will be alleviated, and in water-limited ecosystems where elevated atmospheric 2 will lead to increased water use efficiency of photosynthesis. Considerable changes can be expected above 3 K local temperature change in cold and tropical and above 4 K in the temperate zone. Sensitivity to temperature change increases decreasing precipitation in tropical and temperate ecosystems. In summary, there is a of substantial restructuring of the global land biosphere on current trajectories of change.