By Tom Kenworthy, senior fellow, Center for American Progress.
A new study that looks at the impact of global warming on wildfire patterns in the area around Yellowstone National Park predicts such a sharp increase in large fires by mid-century that the region’s ecology will undergo profound changes, including the failure of some forests to regenerate.
At a pace and scale that surprised the researchers led by professor Anthony Westerling of the University of California-Merced, the Greater Yellowstone Ecosystem will be dramatically altered within a few decades. Now dominated by dense forests, the region will have younger and more open forests, and more grasslands and shrub areas, which will have major impacts on wildlife, hydrology, and aesthetics:
What surprised us about our results was the speed and scale of the projected changes in fire in Greater Yellowstone. We expected fire to increase with increased temperatures, but we did not expect it to increase so much or so quickly.
By 2075, the study predicts that fires on the scale of the 1988 outbreak that burned 1,200 square miles or nearly 800,000 acres could be an annual occurrence. “[Y]ears with no large fires – common until recently – are projected to become increasingly rare,” according to the study which is to be published online this week in the Proceedings of the National Academy of Sciences.
Large, intense but infrequent fires are a natural feature of the Greater Yellowstone Ecosystem. But global warming is rapidly changing that normal fire regime, and frequent big, severe fires will become the norm. The study predicts that after 2050 the average annual area burned in the region will be about 400 square miles, and by 2075 the average area affected by fire will exceed the historic 1988 fires.
“The magnitude of predicted increases in fire occurrence and area burned suggests that there is a real likelihood of Yellowstone’s forests being converted to nonforest vegetation during the mid-21st century because reduced fire intervals would likely preclude post fire tree regeneration,” the study concludes.