Fire + water: Restoring natural fire to California’s mountains
The Illilouette Creek Basin, tucked into the southeastern corner of Yosemite Valley, is surrounded by a natural firewall of pure granite. When a blaze ignites by lightning, it’s not likely to escape.
It’s one of just two wilderness areas in California where fire officials allow lightning-sparked fires to burn by default — with careful monitoring. That makes it an ideal living laboratory for scientists like Sally Thompson, professor of environmental engineering at UC Berkeley, who has used it to study how the frequency of fire affects the movement of water through the landscape.
Thompson’s findings in the basin provide promising new evidence that the sort of natural fire regime seen in the Illilouette Basin can alter local hydrology in meaningful, largely beneficial ways — including sending more water downstream to end users.
Elsewhere in California, suppression is the name of the game: extinguish all flames at any cost. And fire exclusion, widely practiced since the late 19th century with the goals of protecting lives and increasing timber output, has of late been shown to build denser, duff-covered forests that eventually fuel massive, uncontrollable fires. Frequent, moderate-intensity burns in California forests don’t just reduce the risk of catastrophic fire. They also serve an ecological role by promoting biodiversity and the regeneration of fire-adapted native plants.
All of this suggests to scientists that restoring natural fire regimes to California’s mountains could be a win-win-win: more water, improved biodiversity and a reduced risk of catastrophic fires.