[NEWS] The Surprising Science of Wildfires and Tree-Killing Beetles

– by Tara Lohan, September 14, 2016, KQED

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Photo: KQED

So far this year 4,636 wildfires in California have burned more than 200,000 acres. That’s more fires than this time last year and more fires than the five-year average. In fact, in the last few decades, the number of large fires are on the rise across the Western United States and the length of the fire season continues to expand.

There are some areas, particularly in parts of the southern Sierra Nevada, where up to 85 percent of the large trees are dead or dying.
One of the biggest reasons for this is warming temperatures, which are impacting snowpack and ushering in an earlier spring. California has an added challenge of dealing with a five-year drought. The drought and climate change have allowed bark beetles to get the upper hand in swathes of forest in the Sierra Nevada, creating what ecologists call “pulses” of tree mortality. To the average person it looks like a lot of red needles on dead trees.

The Forest Service last estimated some 66 million dead trees in the Sierra Nevada based on aerial surveys – it’s not a huge number compared to the entire region, but the dead trees aren’t spread out evenly across the mountain range. Instead, there are some areas, particularly in parts of the southern Sierra Nevada, where up to 85 percent of the large trees are dead or dying. This rings alarm bells.

One such bell is the role that these beetle-killed trees play in increasing fire danger. Lots of dead trees surely means there is an increased risk of severe wildfires, right? U.S. Agriculture Secretary Tom Vilsack said, “Tree dies-offs of this magnitude are unprecedented and increase the risk of catastrophic wildfires that puts property and lives at risk.” The media have also repeatedly reported that beetle-killed trees are creating a tinder box.

It makes logical sense, but a growing body of scientific research being conducted in the field is revealing otherwise.

READ MORE at KQED

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