[font face=Serif][font size=5]Vicious circle of drought and forest loss in the Amazon[/font]

[font size=4]03/13/2017 - Logging that happens today and potential future rainfall reductions in the Amazon could push the region into a vicious dieback circle. If dry seasons intensify with human-caused climate change, the risk for self-amplified forest loss would increase even more, an international team of scientists finds. If however there is a great variety of tree species in a forest patch, according to the study this can significantly strengthen the chance of survival. To detect such non-linear behavior, the researchers apply a novel complex network analysis of water fluxes.[/font]

[font size=3]“The Amazon rainforest is one of the tipping elements in the Earth system,” says lead-author Delphine Clara Zemp who conducted the study at the Potsdam Institute for Climate Impact Research, Germany. “We already know that on the one hand, reduced rainfall increases the risk of forest dieback, and on the other hand, forest loss can intensify regional droughts. So more droughts can lead to less forest leading to more droughts and so on. Yet the consequences of this feedback between the plants on the ground and the atmosphere above them so far was not clear. Our study provides new insight into this issue, highlighting the risk of self-amplifying forest loss which comes on top of the forest loss directly caused by the rainfall reduction.” This study results from the German-Brazilian Research Training Group on Dynamical Phenomena in Complex Networks at (IRTG1740) hosted by Humboldt Universität zu Berlin.

Self-amplifying effect comes on top of the forest loss directly caused by reduced rainfall

Under a dry-season halving of rainfall, at least 10 percent of the forest might be lost due to effects of self-amplification alone, adding to the substantial direct forest losses from reduced water availability. Computer simulations built by the scientists suggest that this has already happened in the Amazon about 20,000 years ago, in accordance with evidence from the Earth’s past. Still, they stress that the uncertainties are considerable. Taking into account the puzzlements of the vegetation-atmosphere-feedback, self-amplified forest dieback could amount up to 38 percent of the Amazon basin. In combination with the direct effects of the droughts, in fact most of the Amazon forest might eventually be at risk.

The study cannot provide information about the time scales of the processes, it is rather a sensitivity analysis.

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