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This disease has killed a million trees in California, and scientists say it’s basically unstoppable

By Chris Mooney

Healthy forests are especially important at a time of climate change — they’re an incredible tool to remove carbon dioxide from the atmosphere. Dead forests, on the other hand, can light the spark for wildfires, which are already showing a long-predicted uptick in activity.

In California’s coastal forests, health is anything but good. Since 1995, a pathogen that causes a phenomenon dubbed ‘sudden oak death’ (a far catchier name than that of the pathogen itself, Phytophthora ramorumhas taken out millions of oak and tanoak trees, particularly along the coast extending northward from Monterey County. That includes areas of Marin County, Sonoma County and Big Sur.

The pathogen is a water mold that affects different trees differently, and not all are susceptible. It will tear through a forest and kill some trees while leaving others standing.

But in some trees, the pathogen causes tree trunks to crack open a ‘canker’ and literally bleed out sap. The disease is actually related to the pathogen that caused the Irish potato famine in the 1800s.

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Wednesday, May 4, 2016