“Until now, the impacts of climate change on the biosphere have not been quantified very well, certainly not on a global scale,” says Ursula Heyder, lead author of the study now published in the renowned scientific journal Environmental Research Letters. “We wanted to understand comprehensively which amount of warming puts which biotopes under pressure.” Therefore, the research team developed a biogeochemical measure that captures underlying processes in the material cycles. “If something changes here, it is very likely that the concerned ecosystems will change as a whole – down to the smallest bug,” says Heyder. “Because we cannot simulate this whole complexity with a computer, we calculate the risk for such changes considering the processes most relevant to ecosystems.”
The largest changes would probably affect those forests where the cooler climatic zones of the continental interiors of Asia and America transition into moderate latitudes. The study shows that here a larger number of cold-favoring plants could recede because of heat stress, more so than more warmth-tolerant species can take their place. The primeval forests at the Amazon, of significant importance for the world´s climate, are also affected due to possible shifts in their biogeochemical conditions, i.e. shifts in their water and carbon balance.
In cold natural habitats, nature already reacts to a warming of only two degrees– a magnitude already seen as an ambitious target in climate protection. For ecosystems in moderate latitudes, it makes a substantial difference whether temperatures rise by two degrees, three degrees or more: the risk of changes in the flora increase sharply. Up to now, the mitigation of greenhouse gas emissions pledged by a number of states after the Climate Summit in Copenhague sums up to a global warming in excess of three degrees in global means and could hence cause severe environmental changes.
“Nature adapts to climate changes by shifts within the ecosystems,” emphasizes Wolfgang Lucht, co-author of the study and head of PIK´s research domain Climate Impacts and Vulnerabilities. These changes are simply changes, not necessarily good or bad. “But whereas humankind can try to adapt societies to climate change, for example by dyke construction or crop breeding, ecosystems cannot – their change is fundamental,” Lucht explains. “Some simply disappear and are replaced by others.” Some relocate to the North or South, impeded by the speed of change, with impacts that are difficult to foresee. “Ecosystems are a precious good,” says Lucht. “At stake is the natural heritage of humankind.”
The calculations were carried out for 58 different climate projections to study a broad range of possible future developments. This also allowed to differentiate regions with larger uncertainty of the conclusions from those where changes seem certain. All projections show, however, that the majority of Earth´s land surfaces may be affected by moderate or severe changes of environmental characteristics unless comprehensive climate protection succeeds.
Article: Ursula Heyder, Sibyll Schaphoff, Dieter Gerten and Wolfgang Lucht: Risk of severe climate change impact on the terrestrial biosphere; Environmental Research Letters, doi:10.1088/1748-9326/6/3/034036
Weblink to article: http://iopscience.iop.org/1748-9326/6/3/034036
