Saturday, 24 September 2016

California's Historic Drought has Killed Over 66 Million Trees

Plagues devastating forests across the U.S. West – ‘We’re talking millions of trees killed, whole mountain sides dying’

22 September, 2016

By Oliver Milman and Alan Yuhas
19 September 2016

(Guardian) – JB Friday hacked at a rain-sodden tree with a small axe, splitting open a part of the trunk. The wood was riven with dark stripes, signs of a mysterious disease that has ravaged the US’s only rainforests – and just one of the plagues that are devastating American forests across the west.

Friday, a forest ecologist at the University of Hawaii, started getting calls from concerned landowners in Puna, which is on the eastern tip of Hawaii’s big island, in 2010. Their seemingly ubiquitous ohi’a trees were dying at an astonishing rate. The leaves would turn yellow, then brown, over just a few weeks – a startling change for an evergreen tree.

It was like popcorn – pop, pop, pop, pop, one tree after another,” Friday said. “At first people were shocked, now they are resigned.

It’s heartbreaking. This is the biggest threat to our native forests that any of us have seen. If this spreads across the whole island, it could collapse the whole native ecosystem.”

Almost six years later and nearly 50,000 acres of native forest on the big island are infected with rapid ohi’a death disease. Rumors abound as to its origin: did it emerge from Hawaii’s steaming volcanoes? A strange new insect? Scientists still aren’t sure of where it came from or how to treat it. […]

Forestry officials and scientists are increasingly alarmed, and say the essential role of trees – providing clean water, locking up carbon and sheltering whole ecosystems – is being undermined on a grand scale.

California and mountain states have suffered particularly big die-offs in recent years, with 66m trees killed in the Sierra Nevada alone since 2010, according to the Forestry Service.

In northern California, an invasive pathogen called Sudden Oak Death is infecting hundreds of different plants, from redwoods and ferns to backyard oaks and bay laurels. The disease is distantly related to the cause of the 19th-century Irish potato famine, and appears to have arrived with two “Typhoid Marys”, rhododendrons and bay laurels, said Dr David Rizzo, of the University of California, Davis.

We’re talking millions of trees killed, whole mountain sides dying,” Rizzo said. […]

Five years of drought in the west have not only starved trees of water but weakened their defenses and created conditions for “insect eruptions” across the US, said Diana Six, an entomologist at the University of Montana. Bark beetles and mountain pine beetles, usually held in check by wet winters, now have more time to breed and roam. The latter have already expanded their range from British Columbia across the Rockies, to the Yukon border and eastward, into jack pine forests that have never seen the bug.

The outbreak is “something like 10 times bigger than normal, I would argue a lot more than that,” Six said. “Basically a native insect is acting outside of the norm, because of climate change, and become an exotic in forests it’s never been before. We haven’t seen very good outcomes of exotics moving into native forests.” [more]

Progressive forest canopy water stress in California, 2011-2015. Graphic: Gregory Asner / Carnegie Institute for Science

By Robin Azer
17 September 2016

(Snow Brains) – In the Sierra Nevada mountain region of California, the customary green vista associated with a healthy forest has been usurped by a deathly reddish-brown hue. According to the US Forest Service a staggering 66 million trees have died since 2010, with more than a third in the past year alone. 

The death toll has risen sharply due to years of drought and an ever-increasing population of bark beetles. These pesky, hole-boring, eating machines have taken full advantage of the trees’ vulnerability. The result is a huge swath of land infested with an upsurge in bark beetles and millions of dead trees.

Nobody imagined this would come on as fast as it has, or be as lethal,” says Craig Thomas, conservation director for Sierra Forest Legacy, a coalition focused on Sierra Nevada national forest issues. “And nobody really knows what the hell to do.”

Historically, the go-to strategy would be to fire up the chainsaws and remove all the dead trees. In populated areas or those near power lines, it’s still the industry standard. Top government officials including the governor of California, Jerry Brown and Tom Vilsak, U.S. Agriculture Secretary, side with the belief that logging will preempt the risk of catastrophic wildfires. But when the area of destruction covers over 6 million acres, scientists are saying not so fast. After all, those millions of felled trees need to be disposed of, creating a whole new set of problems. Think greenhouse gases. Not to mention the risk to the ecosystems of the remaining plant and wildlife. [more]

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