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California's tree mortality epidemic threatens an increase in wildfires amid ongoing drought

California is in the middle of another busy wildfire season, with 14 active wildfires ongoing. Due to the state's ongoing tree mortality epidemic, officials are concerned that fire dangers could worsen in the coming years.

According to a press release from the California Department of Forestry and Fire Protection (CAL FIRE), aerial survey results conducted in May from the United States Forest Service said that there are over 66 million dead trees in the state since 2010, raising concern for forest health and heightened wildfire danger.

The total number of dead trees skyrocketed from 29 million in 2015 and 3.3 million in 2014. The state's prolonged drought and pesky bark beetles are the two main factors in the increase.

California Gov. Jerry Brown created a Tree Mortality Task Force back in October 2015, which is comprised of over 80 state and federal agencies as well as local governments, utilities and other stakeholders. The task force is currently in the process of removing trees from 10 counties that are said to have the highest hazard.

To help mitigate the wildfire threat, that comes in part from dead vegetation, officials are calling for the public to remove dead trees around their communities.

"The sheer number of dead trees is hard to imagine, but it's real and what we have been anticipating for some time now," said Chief Ken Pimlott, CAL FIRE director and state forester. "We must continue our work to remove dead trees around roadways and critical infrastructure, while homeowners remove dead trees around their homes."

The U.S. Forest Service has already removed approximately 77,000 dead and diseased trees from Stanislaus National Forest, Sierra National Forest and Sequoia National Forest. Due to the sheer volume of dead trees, it's physically impossibly to remove every tree, which is why CAL FIRE said the task force will continue to focus on high priority areas so that infrastructure and escape routes are protected in the event of a wildfire.

Bark beetles native to California are about the size of a grain of rice and have been known to cause tree mortality in western forest and urban environments, but they are not a wholly detrimental nuisance, according to the Forest Service. The dry and hot summers support beetle populations and allow them more opportunities to find homes in dead or weakened trees.

California is in the middle of its fifth year of drought. The latest statistics from the U.S. Drought Monitor show that nearly 43 percent of the state is experiencing extreme drought, which is down from 71 percent just over a year ago.

The lack of water is causing trees to be left in a weakened state, leaving trees unable to protect themselves from the beetles. When trees are healthy and beetle populations are low, trees produce resins or toxic chemicals that can prevent beetles from boring a hole through the bark. However, the Forest Service said that even when trees are healthy, they might not be able to produce enough resins to withstand above-normal beetle populations.

While bark beetle behavior has not changed, climate change is causing them to have shorter hibernations, thus allowing the beetles to spend more time attacking the trees, according to Jiri Hulcr, Ph.D, associate professor with the School of Forest Resources & Conservation at the University of Florida.

"The winters are warmer and the summers are drier," Hulcr said. "These simple facts allow the beetles to reproduce faster and survive the winters better. And so the balance is tipped towards the beetles and away from the trees."

Forests in California are not the only location dealing with a influx of beetles and dead trees. Over the last decade, elevated levels of bark-beetle caused tree mortality have been found in the spruce forests of south-central Alaska and the Rocky Mountains as well as the ponderosa pine forests of Arizona and South Dakota. Hulcr said excessive tree mortality is also occurring in parts of Russia, China, Germany and Japan.

In a recent Union Democrat article, Andrzej Bytnerowicz, a research ecologist with the Forest Service Pacific Southwest Research Station in Riverside, said he thought pervasive tree mortality would affect air quality significantly.

"If fire happens, the dead trees will burn and we will have release of various gases during the fire," Bytnerowicz said. "Toxic gases like nitrogen oxides and sulphur oxides and various organic compounds including benzene."

As researchers continue to examine the impacts of climate change on forest health, other factors being examined include habitat loss, as well as negative economic impacts on timber suppliers.

"The recently released estimates show the voraciousness with which the tree mortality epidemic is gripping California," said Kevin Cann, a member of the Governor's Task Force on Tree Mortality and a Rural County Representatives of California (RCRC) board member. "The situation is dire, not just to those living in rural communities directly dealing with the effects, but to all Californians impacted by the threat wildfires pose to the state's resources."

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