Milman and Yuhas write that warming temperatures "have helped spread four types of beetles that bore into ohi'a bark to feed ... (carrying) disease spore on their wings, in their guts and in the sawdust of burrows, spreading it from tree to tree." Elsewhere on the Big Island, the Pu'uhonua o Honaunau National Historical Park was briefly closed in July while scientists attempted to determine what was killing its coconut and palm trees, among other plants.
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It isn't just Hawaii. In South Miami-Dade county in Florida, "what used to be lush, green fields of majestic avocado trees ... are now acres of blighted groves occupied by withered, fungus-filled tree trunks," according to the Miami Herald. The cause: the redbay ambrosia beetle, which is spreading a fungal disease called laurel wilt; the first record of the beetle, a native of Asia, in the U.S. was in 2002 in Georgia, where it likely arrived in solid wood packing material.
In Harvard Forest, in the Great Smoky Mountains National Park and elsewhere in the eastern part of the country, another invasive insect -- the hemlock woolly adelgid -- is taking advantage of warming temperatures to spread among eastern hemlocks, which it kills by eating the trees' vital stored starches. A die-off of aspen in Colorado was due primarily to water stress as a result of drought; while in Washington State, "from mountain forests to city parks, trees that suffered terribly in (a 2015) drought are dying, and burgeoning pests are taking advantage of stressed trees struggling to hang on. Statewide, officials are seeing trees with red needles, dead tops, dying branches, dropped needles and other signs of stress."
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California has been heavily affected. Milman and Yuhas report that in the northern part of the state, an invasive pathogen called Sudden Oak Death is infecting hundreds of plants, "sapping the life" from oaks and other trees and turning them brown. In the Sierra Nevada, a "lethal combination of drought, heat and voracious bark beetles ... killed 26 million trees" between October 2015 and June this year; officials estimate that 66 million trees have died in the state since 2010.
Milman and Yumas note that such widespread tree deaths will likely have cascading impacts, from depriving birds and mammals of their food to undermining the fundamentally essential role that trees play: "providing clean water, locking up carbon and sheltering whole ecosystems."
In California, officials have a more immediate concern. Such a large number of dead and downed trees in effect provides vast amounts of kindling for drought-influenced forest fires: victims of climate change literally fueling one of global warming's most destructive impacts.
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