Researchers in Germany have developed a new generic metric that enables ecosystem change, as projected by different climate models, to be compared in a quantitative way.

"Ecosystems are immensely complex and their responses hard to predict, which is why we used chemical shifts as an indicator of danger to their stability," Wolfgang Lucht from the Potsdam Institute for Climate Impact Research told environmentalresearchweb.

"Different climate models will give different patterns of change for the same ecosystem because of inherent uncertainty in their projections. We wanted to devise a way of measuring the risk of change in an ecosystem that can then be used to compare results across a range of climate-change projections from different climate models. This then enables us to assess how high the risk is that a particular ecosystem will suffer due to climate change."

The team's generic ecosystem stability index (capital Gamma, Γ) is a measure of biogeochemical shifts and vegetation structural changes in land ecosystems. It is based on relative and absolute changes in carbon and water fluxes and stores, changes in their balance and changes in vegetation composition.

For example, a boreal mixed forest that is predicted to change to a temperate mixed forest would have a generic ecosystem stability index (Γ) of 0.2; whereas a Γ of 0.98 would represent a tropical rainforest that is predicted to become a desert (or vice versa).

Lucht and his colleagues, including lead author Ursula Heyder, used Γ to compare projected ecosystem change across different climate models under various IPCC emission pathways.

"We found that Europe has the lowest risk of change and Africa has the highest risk," said Lucht. "We also found that there were some regions, such as the Himalayas, where most climate models agreed that there will be considerable change by the end of the century. There are almost no regions of Earth without any risk of severe change."

The regions marked in red in parts (a) and (b) of the figure represent areas where all or most of the climate models agree a change will happen.

However, the researchers also found that there were many areas, such as in South America, where there was not a consensus among climate models. "Just because only a few models project change in these regions, it does not mean change will not happen," warns Lucht. "We have no way of knowing which climate model will turn out to have been right, so there is still a risk of change in these regions before the end of the century."

The researchers published their work in Environmental Research Letters (ERL).

(By Nadya Anscombe, Environmental Research Web, 01/11/2011)