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Hot and dry conditions triggered by climate change are killing the world's trees, according to a new report which examines dozens of scientific articles on the subject. Stanford University graduate student William Anderegg has seen this forest die-off firsthand. His doctoral thesis documents the impact of drought on trembling aspen, the most common tree in North America. “These are complete hillsides of trembling aspens that are dying off," Anderegg says. "And when the main tree in a forest goes, you tend to see a lot of the other species, especially the grasses and the wild flowers, tend to disappear as well. But you lose a lot of those species from those forests.” Changing ecology With colleagues from Stanford and North Arizona State University, Anderegg co-authored the new report which presents a picture of accelerating worldwide tree deaths that appear to be linked to changes in the global climate. Anderegg says these changes, triggered by rising levels of heat-trapping gases in the atmosphere, are stressing the world’s forests. “One of the ways that we expect climate change to increasingly play out in forests is through these widespread tree mortality events where you stress the trees enough that you essentially push a whole region of them off the edge and in fact what happens afterwards, after a forest dies from drought is every bit as important and in some sense matters more to humans who rely on forests.” | 
