© David McNew/Getty Images Oak trees at dusk near in California. The state has seen more than 66 million trees killed in the Sierra Nevada alone since 2010.
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.
