“Less tree cover also means less water usage,” he said.
Stephens said research shows that after a century of firefighters suppressing forest fires, rather than letting them burn, water that flows into streams has diminished.
“It’s just hugely important that we have change that trajectory in big scales; we’re talking about hundreds of thousands of acres—not 5,000. We’re talking big areas,” Stephens said.
“If we don’t do this, we’re really going to look back at this period right now in 30 years and say, ‘this is a huge missed-opportunity.”
He said in Yosemite National Forrest, for example, there were 40 fires allowed to burn out over decades and that his study shows that, as a result, there was more water supplies in streams in rivers.
In addition, Stephens said, that with more trees in the Sierra, the more snow that collects on them and evaporates, rather than feeding surface water.
Other scientists, however, argue that the more trees there are, the better because they help remove carbon dioxide from the air, which they say contributes to global climate change.