29 Million Trees Have Died in California From Bark Beetles, Drought

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Ongoing drought conditions have contributed to the 29 million tree deaths in California, a number that is still on the rise. In addition to millions of oak trees in the state being killed off by sudden oak death disease, bark beetles have also played a large role in taking out the timbers.

“The tree mortality that we’re experiencing, it’s really unprecedented," California Department of Forestry and Fire Protection Director Ken Pimlott said in a video for the California State Association of Counties (CASC). "Unless you get into the Sierra Nevada, and particularly the central and southern Sierras, you don’t necessarily understand the gravity of it.”

The California counties of Amador, El Dorado and Placer have temporarily been added to the list of those most directly impacted by tree mortality, according to CASC. After findings from a flyover measuring tree mortality are released, they will join six others to be eligible for more assistance from the state to deal with the widespread tree die-offs. 

Conditions from the drought have weakened the trees, which then succumb to the impacts of the bark beetles that travel from tree to tree.

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Since 2010, an estimated 40 million trees have died in the Golden State's national forests as a result of these stressors, according to the United States Department of Agriculture. The high numbers of dying trees are significantly impacting the people who live or work in these areas, as well, as there is a higher number of hazardous trees in and around communities and campgrounds and along trails, roads and power lines.

Cutting down trees affected by sudden oak death has been the only way officials have managed to keep the disease from spreading, PNAS reports. But it's too little too late. If officials had started attempting to control the epidemic more than 10 years ago, they may have had a chance.

“Even if huge amounts of money were to be invested to stop the epidemic starting today, the results of our model show this cannot lead to successful control for any plausible management budget," Dr. Nik Cunniffe of Cambridge's Department of Plant Sciences, and lead author of the study published in PNAS, said in a press release from the university. "We, therefore, wanted to know whether it could have been contained if a carefully optimized strategy had been introduced sooner. Our model showed that, with a very high level of investment starting in 2002, the disease could not have been eradicated, but its spread could have been slowed and the area affected greatly reduced.”

The mass die-off has dire environmental implications.

(Nik Cunniffe)

Millions of acres of land have been affected in coastal California,” Richard Cobb, who studies the disease at the University of California, Davis, told the Washington Post. “It spreads via wind and rain, and it’s made some really big jumps to different parts of the state and into Oregon. It probably spread into California via the nursery trade. And it has been moved around the country a lot, also within the nursery trade.”

What's worse, the epidemic will spread almost 10 times the area it affects today. By 2030, it could infect more than 5,000 square miles.

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This year in particular, scientists will keep a close eye on the disease. According to the California Oak Mortality Task Force, the high levels of rain so far this year mean that the disease is likely to spread even more than usual. The group is calling on volunteers to help track and gather samples of trees that could be affected by the disease.

“We won’t be able to avoid much of the ecological impacts of losing all these trees,” Cobb said in an interview with the LA Times. “But there is still time to avoid the worst possible outcomes of this epidemic by prioritizing trees that are most at risk and taking steps to protect them.”

The silver lining? This experience provides valuable information for outbreaks in the future.

“It is a tool by which we can make a better job next time, because it is inevitable that there will be a next time,” Professor Chris Gilligan, a senior author in the study, said in the press release. “With this sort of epidemic, there will always be more sites to treat than can be afforded. Our model shows when and where control is most effective at different stages throughout a developing epidemic so that resources can be better targeted.”

Last year California Governor Jerry Brown declared tree mortality a statewide emergency and set up a task force to begin assessing and managing the problem, according to the CASC. Headed by CalFire, the task force includes representatives from state agencies, local governments and utilities. 

Governor Brown has also designated $161 million in the state budget to forest health and to help deal with tree mortality.

Learn more at weather.com