California's historic drought is having a major impact on the state's forests.
According to an aerial survey conducted last month by the U.S. Forest Service, approximately 12 million forest trees have died in Southern California and the southern Sierra Nevada mountains over the last year. The report credits unusually high temperatures, a diminished snowpack and a severe lack of rainfall with drying up the trees, leaving the region susceptible to forest fires.
Of the more than 4.2 million acres surveyed in Southern California, researchers found 164,000 acres with high tree mortality. They found approximately 2 million trees had died over the last year.
In the southern Sierras, researchers found over 10 million perished trees in 4.1 million acres. There, mortality is "widespread and severe" in the foothills among ponderosa, gray pine, blue oak and live oak trees.
Jeffrey Moore, the acting aerial survey program manager for the region, told the Los Angeles Times he expects the mass tree mortality to continue throughout the summer.
“It is almost certain that millions more trees will die over the course of the upcoming summer as the drought situation continues and becomes ever more long term and as bark beetle populations continue to expand," he said.
California is in its fourth year of drought, with precipitation levels far below normal across the state. According to the National Drought Mitigation Center, 66.6 percent of the state is currently experiencing severe or exceptional drought.
The rainfall deficits have prompted Gov. Jerry Brown (D) to impose the state's first-ever mandatory water cutbacks, calling for reductions of 10 to 35 percent from 2013 usage levels. Violators could face fines up to $10,000.
"Today we are standing on dry grass where there should be five feet of snow," Brown said in a statement last month. "This historic drought demands unprecedented action."