A new study has found that wildfires are inflicting increasingly severe damage to forest ecosystems in the Sierra Nevada - and climate change is a big reason why.
The study in the October issue of the scientific journal Ecosystems comes in the wake of earlier work that has tied global warming to more frequent fires - and a longer fire season.
The new study - by two U.S. Forest Service researchers and three university scientists - tracked the intensity of wildfire and found that the extent of "high severity fires" - those that destroy entire stands of forest - has grown significantly since 1984.
Part of the problem, the researchers point out, is a long-standing pattern of fire suppression that has allowed Sierra forests to grow unnaturally dense and become littered with brush and woody debris. But climate change is feeding the flames as well. "The patterns we see in the climate-fire relationship are clearly due in part of increasing temperatures," they write.
The Moonlight Fire in Plumas County, pictured at left, is a kind of poster child for this new era of intense, destructive fire. It began during hot, windy conditions over the Labor Day weekend of 2007. By the time it was brought under control, more than one third of the fire burned so thoroughly federal officials classified it as high severity. Drive through those badly burned areas today and you see no living trees across wide swaths of terrain. Even big old ponderosa pines, such as the one pictured below, that have survived many natural, cooler fires over the past two to three centuries were killed in the Moonlight fire.
"Through their growing tendency to kill larger patches of canopy trees, contemporary fires are contributing to increasing levels of forest fragmentation," the authors of the Ecosystems paper wrote. The scorched-earth blazes also threaten to increase soil erosion and stream sedimentation and hurt natural forest regeneration, they said. And the future does not look good.
"With peak snow-melt coming earlier, fire season lengthening, the summer drought deepening and forest fuels at possibly all-time highs, it may simply be that most low- and middle-elevation forests in the study region are ready and primed to burn," the authors said, adding:
"In light of recent alarming projections for increased temperatures ... by the end of the century, a major rethinking of current fire and fuels management strategies may be in order."
U.S. Forest Service regional ecologist Hugh Safford and remote sensing specialist Jay Miller - both based in California - led the study team.
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