A few weeks ago, a German tourist hiking the Trail of 100 Giants in Sequoia National Forest witnessed the fall of a pair of giant sequoia, estimated at some 1,500 years old. Now the USDA Forest Service must decide how to incorporate these now-resting behemoths into its trail system and the natural landscape.

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• Read the Los Angeles Times article by Bettina Boxall about the sequoia fall

Though the crash itself is dramatic, it was simply a natural end to the long-life of an organism. As USGS research ecologist Nate Stephenson told the Los Angeles Times:

"Sequoias do fall. That's how big sequoias die... It's never anything that I consider with alarm."

Stephenson is a lead scientist at the Sequoia and Kings Canyon Field Station at the USGS Western Ecological Research Center. Stephenson and his WERC colleagues have been analyzing tree deaths in the western United States, as part of their research focus on forest ecology.

What is alarming is a 2009 study led by Stephenson and WERC colleague Phil van Mantgem, where they found that tree deaths have doubled across the western U.S. in recent decades.

Regional warming of temperatures -- with consequences such as reduced snowpack and lengthened summer droughts -- may be stressing many western tree species. And just as with humans, when trees get stressed, they become more prone to diseases.

Stephenson, van Mantgem and their research partners through the Western Mountain Initiative are continuing to examine how mountain ecosystems -- such as the sequoia and redwood groves of California -- are faring under changing global conditions.

-- Ben Young Landis