Wildfires and Drought Shape California's Ecology

California is no stranger to drought - the state is in the middle of its third utterly rainless year. And this lack of water and arid air creates the perfect scenario for wildfires, which have recently wreaked havoc across the state. Researchers have found that wildfires and drought combined shape the ecology of California, both past and future.

Lead author and ecologist John Keeley says understanding historical fire trends is important during fire discussions so that people realize they are talking about two distinct fire schemes in two different ecosystems: the mountain forests and the lower elevation chaparral, oak woodlands, and grasslands.

The chaparral shrublands of southern California, and similar sagebrush ecosystems in the Great Basin, are not adapted to the kind of frequent fires typical of the mountain conifer forests in California. Fires in the lower elevation ecosystems are always crown fires, which kill most of the vegetation. Before humans arrived on the planet, these ecosystems burned for 100 to 130 years.

But in this past century, these lower elevation ecosystems have experienced unprecedented fire frequency, with wildfires returning to the same area every 10 to 20 years, altering the ecology of the landscape.

"In Southern California, lower elevation ecosystems have burned more frequently than ever before. I think it's partly climate, but also people starting fires during bad conditions," Keeley explained in a press release.

Bad conditions refer to extended droughts and dry fall days when the Santa Ana winds blow through the canyons.

But high elevation conifer forests are used to wildfires, which are brought on by spring temperatures and drought. Such areas include the hotter, drier valleys and foothills cloaked in grass, oak, and chaparral. It is these regions where human activity is more common, which also explains why 95 percent of California wildfires are started by people - whether arson or accident.

"Climate change is certainly important on some landscapes. But at lower elevation, we should not be thinking just about climate change," said Keeley. "We should be thinking about all global change."

Wildfires are not bad news for all vegetation though. Several exotic grasses have capitalized on these frequent fires and spread invasively to other regions.

Keeley and other ecological scientists will present their findings in detail at the upcoming 99^th Annual Meeting of the Ecological Society of America on Aug. 10-15.