JOIN USWhen beetles attack forests
This winter has been the warmest on record in much of New England, USA. And while many people enjoyed the T-shirt weather, it made Claire E Rutledge, a researcher with Connecticut’s Agricultural Experiment Station, more concerned about what next season may hold. Beginning in April, she will head to Wharton Brook and other state lands, setting traps for the southern pine beetle and checking them weekly through midsummer.
The beetles, which can kill thousands of trees in epidemic attacks, had never been found beyond the pitch pine forests of the American South, because the winters were too cold. But they have migrated to New Jersey, where they have destroyed more than 30,000 acres of forest since 2002. And the warmer winters have now beckoned them to New England. Alarmed scientists first discovered the beetles last year along a front stretching more than 200 miles, from central Long Island to Cape Cod and Martha’s Vineyard, a region long thought to be far too frigid for these tiny beetles, barely different in size and colour from a chocolate sprinkle. “When I heard they caught a live beetle in Massachusetts,” Claire said, “that really freaked me out.”
Now that the beetles are in New
England, they are probably there to stay, state and environmental officials said. And if there is a severe outbreak, the region could lose much of its pitch pine forests. Many of the forests are already unhealthy, a result of overcrowding, making them especially susceptible to the pine beetle’s attacks and many state forestry divisions do not have the resources to combat them.
At risk
Scientists are concerned that the beetles could destroy the remaining tracts of the pitch pine forest, an ecosystem that once carpeted the Eastern Seaboard but now exists mostly in pockets — the Cape Cod National Seashore, the Albany Pine Bush Preserve and smaller forests — and is home to more than a dozen endangered species, such as the tiger beetle and several types of butterflies. “I don’t think people have a strong understanding of how at risk these forests are,” said Kevin J Dodds, a scientist who runs the southern pine beetle response in the Northeast for the U.S. Forest Service.
An invasion in New England could mean a repeat of what happened in New Jersey and on Long Island, where state agencies were caught off guard, officials say. “We’re still scratching our heads and asking why we didn’t find this sooner on Long Island,” said Robert Davies, New York’s state forester. By the time they had discovered the infestation, he said, it had ballooned to 10,000 acres. State environmental officials and federal foresters warned Connecticut that the plague could be headed their way toward the end of 2014, and soon after, they found infested trees in about 20 places across the state.
Some scientists see the beetles’ march north as another sign that climate change is disrupting the environment, and not just in ways that damage ecosystems. Heat-loving creatures like ticks and mosquitoes are expanding their ranges, too, carrying illnesses like Lyme disease to Canada and dengue fever to parts of the United States. And the environmental costs are steep, too. For all the damage wrought by the southern pine beetle, the mountain pine beetle has exacted a far greater toll, ravaging pine forests across the western United States and Canada, destroying tens of millions of acres in places and altitudes once thought beyond their reach.
Necessary precautions
According to Matthew P Ayres, a Dartmouth College biologist who studies the southern pine beetle, the warming of winter’s coldest night is the primary cause of their spread. Most beetles die if temperatures fall to around minus 8 degrees Fahrenheit. And while this winter had an unusually cold snap, the low temperatures did not last long enough to wipe out the beetles, Claire said.
Robert said, “We were still hearing about beetles flying on Christmas Day, and that’s not a good thing.” Kevin and others say that many long-standing practices unintentionally damaged the forests. They were largely left to themselves, resulting in overcrowded stands, where trees had to compete for sunlight and nutrients. In crowded forests, beetle attacks can spread more easily, and the beetles thrive in unhealthy forests like these because they can overwhelm a tree’s defences by laying eggs that, when hatched, hijack the tree’s circulatory system, and also carry a fungus that clogs the tree’s waterways.
With this one-two punch, beetles can wipe out thousands of trees in a season, Claire said. Natural fires, for all the damage they cause, do thin forests and lead to regrowth, but states have worked quickly to extinguish them. Trees have some defences mechanisms — they release resin, which hardens into little yellow clusters on the bark to fill the holes made by beetles and kill them — but they do not always work.
This spring, scientists and state officials will set more traps in New England and New York. Depending on what they find, they may conduct aerial surveys to see if any trees are in distress. When the trees are in trouble, their needles turn from green to yellow and red, an effect that can be seen best from above. Matthew said that if precautions were not taken, a widespread invasion could leave only a few pitch pines in the region. “It’s an example of something that’s happening all over the world,” Matthew said.