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Drought Impacts Leave Trees Vulnerable to Invasive Bark Beetle, Other Diseases

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Ongoing California drought impacts trees

Drought can have numerous impacts on area soils, trees, and ecosystems, much of which can allow invasive species to attack native vegetations, and, in some instances, can cause massive tree death. California forests are facing the impacts of drought on a wide scale, including both sudden oak death and effects of the bark beetle.

Information compiled in a [link url=”” title=”recent analysis by The Weather Channel”] showed how California forests have been dying due to sudden oak death, and also, due to weakened tree conditions from the ongoing drought, how trees in the state are now being killed by the invasive bark beetle.

Scientists attribute the death of more than 29 million trees in 2015 to ongoing drought conditions, and that number is still rising, thanks to the bark beetle. Conditions are most noticeable in the southern and central Sierra Nevada Range, but the Stanislaus and Sequoia National Forests are also being impacted. The [link url=”″ title=”U.S. Forest Service also noted that three other national forests”] are being affected to a slightly lesser degree: Los Padres National Forest, Tahoe National Forest, and Eldorado National Forest.

Controlling the spread of disease

A [link url=”” title=”study released by PNAS”] (Proceedings of the National Academy of Sciences) found that treating infected trees at the outset of a disease outbreak, such as with the sudden oak death, is highly beneficial for improving control of its spread.

That option is no longer viable, as the epidemic began more than 10 years ago, and due to its expansion, there simply would never be enough funding to treat all the trees currently infected. To make matters worse, scientists expect that by the year 2030, the disease is likely to multiply to an area 10 times its present size, with devastating impacts on coastal California and its ecosystems.

Due to the extent of the tree death, California Governor Jerry Brown established the [link url=”″ title=”Tree Mortality Task Force headed by Cal Fire”] in 2015. The task force assesses and manages ongoing problems with members from local and state agencies and utilities.  

The task force noted that part of the concern is the death of trees that impact neighborhood safety from hazardous trees that may fall on power lines or roads and injure people or cause damages.

State assistance for affected counties

The California State Association of Counties (CSAC) reported that a total of nine counties are on a list considered to be highly impacted by tree mortality and eligible for state assistance. The original six counties included Fresno, Madera, Mariposa, Tulare, Tuolumne, and Calaveras. Three more have been added: Amador, El Dorado, and Placer. Once approved after area flyovers, counties become eligible for the state’s assistance in combating tree mortality.

Cumulatively, an estimated 40 million trees have died since 2010 due to climate change, drought, high tree density, and bark beetles.

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Kimberly Arsenault serves as an intern at the Cleveland/Bradley County Emergency Management Agency where she works on plan revisions and special projects. Previously, Kimberly spent 15 years in commercial and business aviation. Her positions included station manager at the former Midwest Express Airlines, as well as corporate flight attendant, inflight manager, and charter flight coordinator. Kimberly currently holds a master's degree in emergency and disaster management from American Public University.

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