Richard Perry/The New York Times
In Mays Landing, N.J., last month, Nick Bleyhl cut a pine tree whose yellow needles indicated infection by southern pine beetles. He was part of a crew working for the state forest service to curb the spread of the insect, now endemic.
BLUE ANCHOR, N.J. — "Heads up!"
Deep in the woods, the whine of chain saws pierced the fall air, and Steve Garcia shouted a warning to fellow loggers as a 40-foot pitch pine crashed to the ground.
He was chopping down trees to save the forest as part of New Jersey's effort to beat back an invasion of beetles.
In an infestation that scientists say is almost certainly a consequence of global warming, the southern pine beetle is spreading through New Jersey's famous Pinelands.
It tried to do so many times in the past, but bitterly cold winters would always kill it off. Now, scientists say, the winters are no longer cold enough. The tiny insect, firmly entrenched, has already killed tens of thousands of acres of pines, and it is marching northward.
Scientists say it is a striking example of the way seemingly small climatic changes are disturbing the balance of nature. They see these changes as a warning of the costly impact that is likely to come with continued high emissions of greenhouse gases.
The disturbances are also raising profound questions about how to respond. Old battles about whether to leave nature alone or to manage it are being rejoined as landscapes come under stress.
The New Jersey situation resembles, on a smaller scale, the outbreak of mountain pine beetles that has ravaged tens of millions of acres of forest across the Western United States and Canada. That devastation, too, has been attributed to global warming — specifically, the disappearance of the bitterly cold winter nights that once kept the beetles in check.
In contrast to the West, where dying evergreens are splayed across steep mountainsides for all to see, the invasion in New Jersey has received barely any notice. The state's pine forests occupy relatively flat land, and the scope of the damage is obvious only from the air.
"It's a tremendously serious issue, but it hasn't gotten anybody's attention," said State Senator Bob Smith, a Democrat from Piscataway and the chairman of the Environment and Energy Committee.
Scientists and foresters say the lack of public pressure has meant that the state has been slow to mount an adequate response. They are worried that the beetles will not only devastate the Pinelands, but will also eventually attack coastal pinelands on Long Island and Cape Cod.
In New Jersey, the beetles hit a peak in 2010, when they killed trees across 14,000 acres of state and private land. More recently, the damage has been a few thousand acres per year. But with the beetle now endemic in New Jersey, experts do not think that reprieve will last.
"I'm worried about when we really get a superstress on the trees," said George L. Zimmermann, a forest ecologist at Richard Stockton College of New Jersey, in Galloway. "If the beetle takes off, you could be talking not tens of thousands of acres, but a hundred thousand or more."
Historically, it was too cold for the beetles to live north of Delaware. In their native habitat in the South, they are always present at low levels, surviving by attacking diseased or weakened pine trees.
The beetles, no bigger than uncooked grains of rice, burrow through a tree's bark and consume a layer of tissue that provides the tree with nutrients and water. As the evergreens starve to death, they take on the color of a broadleaf forest in autumn.
Healthy trees can fight off small numbers of beetles by exuding a sticky sap that pushes them out. But a large beetle outbreak can overwhelm even vigorous trees. "The way they kill trees is the way wolves kill a moose — they do it by numbers," said Matthew P. Ayres, a Dartmouth biologist who studies the beetles.
New Jersey has warmed by about 2.3 degrees Fahrenheit over the past century, but that average obscures the change that really matters.
Winter nights of about 8 degrees below zero are needed to kill most beetles. The New Jersey climatologist's office calculates that such bitter nights used to happen several times per decade in the state. But the last night that cold in the Pinelands was in 1996, and the beetle outbreak was first noticed five years later.
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