We have shaped the forest in other ways, too. Chestnut trees once accounted for perhaps a quarter of the Eastern forest. But they were wiped out by the 1950s by an Asian fungus brought here on Japanese nursery stock. A shipment of logs from Europe in 1931 introduced Dutch elm disease, another fungal blight, which infected elms across the Northeast. The European gypsy moth, let loose in Massachusetts in the 1860s, has ravaged oaks and other trees, and the hemlock woolly adelgid, an Asian insect introduced to the East Coast in 1951, has caused widespread mortality in hemlocks. Another invasive Asian beetle, the emerald ash borer, is destroying millions of ash trees in the Midwest and Middle Atlantic. The cumulative effect of these and other pests and pathogens is a more homogenous forest, and one that is more vulnerable to invasion. "We're setting ourselves up for more catastrophe," Foster said.
Forests are becoming even more fragile as the climate warms and the range of native forest pests expands. In the Rocky Mountains, hundreds of thousands of acres of aspen have begun to succumb to the combined pressures of drought, disease, warmer weather and insect predation—a phenomenon termed "sudden aspen decline." Pine trees there are dying in even greater numbers: mountain pine beetles, aided by drought and mild winters, are laying waste to millions of acres.
As the evening grew dark, Foster and I turned back toward his office. We stopped at the edge of the forest, and we could see barns and a snow-covered field and the distant lights of a farmhouse. From where we stood, the Worcester outbreak was less than 40 miles away. I wondered what the beetle might do were it to make it here to the Harvard Forest, which harbors some of the oldest woods in all of Massachusetts.
"Even if it comes through here," Foster said, "there'll still be a forest. It may not be the same, but the forest will continue." He kicked at the snow with the toe of one boot and looked out over the field. "It is such a generalist, though," he said of the beetle. "It likes so many trees. I don't know. It really is one of the worst nightmares."
On the night of december 11, 2008, a freezing rain fell over Worcester, and in the hours before dawn Clint McFarland woke several times to the patter of sleet against his window. In the morning, when he stepped outside, he hardly recognized the city. Under a burden of ice, trees had fallen haphazardly onto cars and houses. Limbs littered the streets; nearly half the roads in Donna Massie's neighborhood were impassable. The ice storm, the worst in a decade, had blanketed much of the Northeast, leaving nearly a million homes and businesses without power, injecting an unforeseeable element of chaos into an already complicated beetle eradication effort.
Contractors up and down the East Coast, from as far south as Florida, began arriving in the city in pursuit of debris-removal work, many of them unaware of the ordinance against removing wood from a quarantined area. In the days after the storm, several trucks were seen carting tree limbs away, despite patrols by environmental police. "We know that wood has been moved out of the city," McFarland told me when I caught up with him the following week. "That's our paramount concern right now. It can't happen again."
Driving to a meeting of town officials, McFarland looked beleaguered. He'd been working nearly nonstop for days, and weighing upon him was the thought that he would have to tell his wife he was going to miss Christmas. The ice storm, meanwhile, had pushed back plans to begin cutting and chipping trees, and the tally of infested trees in the quarantine area had risen to nearly 6,000.
We passed streets lined with shoulder-high stacks of branches. On one block, nearly every tree along the road had been marked for ALB-related removal with an ominous red splotch. I asked McFarland if he thought much about what would happen if he failed in Worcester. He laughed and admitted that he did. "But it's in my nature. I have a fear of failure." He smiled. "Look, we can do this. I've been studying this beetle for years and I think eradication is really possible, and that's hard to say about most insects. And we don't have a choice, do we? There is so much at stake. If it hits the Northeastern hardwood forest, you're looking at the maple industry, timber, tourism. It's huge. We really can't fail."
A year later, there is reason for some optimism. The government's containment efforts have so far succeeded. More than 25,000 trees were felled within Worcester city limits in 2009. The area of quarantine around the city has expanded slightly, from 62 to 66 square miles. No new ALB infestations have been discovered outside the city center.
At the height of the crisis in the winter of 2008-2009, log loaders and bucket trucks were arriving by the hour from out of state, and chain saw crews were removing wood from backyards and rooftops and utility lines. Given the concentration of human effort marshaled against a single insect, it was tempting to think that this was the only battle against an invasive species. Yet in California, Virginia, Michigan and Florida—to name just a few affected states—the same drama was unfolding, if with different characters: the emerald ash borer and the hemlock woolly adelgid, sudden oak death and the citrus canker. Beyond our borders, more organisms are poised to invade. On average, we bring a major new agricultural pest into the country every three or four years. Cornell's Hoebeke told me that perhaps as many as 600 of the world's high-risk insect pests were not yet established in the United States, any one of which might prove as virulent as the ALB. He was particularly concerned about the Asian citrus longhorned beetle, which could devastate the country's citrus and apple orchards.