Now scientists are calling it something else: a possible climate change lesson.
The 500 acres of dead oak trees were the epicenter of an islandwide infestation of caterpillars that munched their way through millions of leaves for three consecutive springs ending in 2007. Then a severe summer drought hit the island, finishing off tens of thousands of the weakened trees.
“I have never seen anything like what has happened on Martha’s Vineyard in New England,’’ said David Foster, a Harvard University ecologist. “Usually you walk through forests and see some dead trees, but here, it’s hundreds of acres and almost all of the trees in it are dead.’’
Ordinarily, such catastrophic damage would be chalked up to bad luck. But Foster, who is also director of Harvard Forest, the university’s experimental forest in Petersham, and other researchers recently discovered a vast die-off of Cape Cod coastal oak trees 5,000 years ago during an abrupt warming period. They found evidence of the forest’s demise in sediment samples from under lakes and ponds, and they speculate that the ancient - and far smaller contemporary - episodes may have roots in the same type of one-two climate punch: more-active bugs coupled with an intense drought.
Scientists predict that in a warming world, insects will thrive, and droughts and other extreme weather will become commonplace. With the prospect of more numerous bugs feasting on weakened trees, Foster wonders whether the recent die-off is a harbinger of more catastrophic ones in the future. While the dead trees will certainly be replaced by new ones, what species repopulate forests has ramifications for everything from lichen to leaf-peepers.
“These trees control the foundation of an ecosystem,’’ said Foster, whose group has just been awarded $100,000 from the National Science Foundation to study the Vineyard forest. “What happens when they collapse? We are trying to understand how everything in that forest copes.’’
Nobody foresaw the death of the oaks. In the spring of 2004, an intense caterpillar infestation gripped the trees for two weeks, raining thousands of inch-long green-and-gray caterpillars on the heads of islanders and visitors.
Many thought the bugs were the despised European winter moth that shows up in horror-movie-like numbers off the island, but scientists were able to confirm that most of the bugs were a native fall cankerworm. Not that the news was much better: Cankerworm moth numbers were legendary that winter when they emerged as adults, splattering car windshields so thoroughly that drivers could hardly see.
“The first year, it was a shock’’ that the leaves were disappearing so quickly, said Tim Boland, executive director of the Polly Hill Arboretum in West Tisbury, as he picked his way last week over lichen-covered dead oak branches that littered a narrow Arboretum path.
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