The Northern Forest Fire Burned Because It Wasn’t Being Feeded the Water

A single, devastating California fire season wiped out years of efforts to cut emissions from a huge area of California forests on the West Coast. But a key tool for fighting forest fires doesn’t work as well in dry years.

The drought — which has stretched across the western United States since late 2011 — made the Northern Forest Fire burn more aggressive because it burned in areas that had been dry for years. The dry weather made the fire larger and more destructive.

Last year’s fire season, which burned nearly 150,000 acres across California, was the largest in state history, burning nearly six times as much land as last year’s fire season.

In a recent study, University of California, Berkeley, scientists found that the forests burned because they weren’t being fed enough water from the snowpack in the Rocky Mountains. Instead, the trees at the center of the fires received a small fraction of the water. The scientists think they’ve identified the reason the forests burned so intensely: That’s because more water fell as rain than fell as snowpack, which means more evaporation, which makes the water even more effective at speeding fires spread.

“We saw a very dramatic increase in the amount of fire that was being fueled in the last two and a half years. That’s a very different climate and fire regime than we’ve had in the last two and a half years,” said Susan St John, a UC Berkeley professor who co-led the research.

The research, published online Monday in the journal Environmental Research Letters, suggests that drying up the forests can be addressed in a manner similar to combating droughts across California.

“We did find that in wet years, we see a slowdown in fire activity,” St John said. While forests that received little snow last winter were still extremely dry, they were not burning out of control. “We had no evidence of fires in those areas that were going out and burning in very large quantities.”

That’s due in part to the trees’ ability to soak up the moisture, much like a sponge. The scientific word for this phenomenon is transpiration, a fancy word for sap that makes its way from the branch to the trunk and then out of the crown. As these trees absorb more water during the dry season, they draw

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