From today's New York Times is an article describing a new study showing that rising temperatures and accompanying drought are causing Western trees -- like these -- to die at approximately twice the rate of just a few decades ago. Below the picture is an excerpt from the article.

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It remains unclear how much of the regional warming is a result of a natural climate cycle and how much results from a global trend toward higher temperatures. But Jerry F. Franklin, a professor of ecosystem analysis at the University of Washington and an author of the study, blamed global warming. “We see the regional warming as part of a much larger shift globally,” Mr. Franklin said.

The study focused on forests more than 200 years old where rapid changes in demographic rates would more likely be caused by environmental changes rather than by internal processes like self-thinning that are more common in young forests. The spike in mortality cannot be attributed to aging, fires and other events, the researchers said

Warmer weather makes trees more vulnerable to insects and pathogens that thrive in warmer conditions.

In a report last year, the Department of Agriculture said that climate change had “very likely” increased the size and number of fires, insect infestations and overall tree die-offs in forests in the West, the Southwest and Alaska, and that the damage would accelerate in the future.

The authors of the new study said in a teleconference that if tree mortality rates continued to rise, the average size of trees could fall because trees would die at younger ages. Smaller trees cannot store as much carbon dioxide as large ones.

In addition, areas could also become less suitable for some species and more welcoming for others, and existing species might begin to act in peculiar ways. “Novel behaviors on the part of pests and pathogens are the sort of thing we’ll get surprised by,” Mr. Franklin said.