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Damage from invasive forest pests costs billions a year, study finds

The emerald ash borer has devastated trees across Massachusetts over the past few years.
The emerald ash borer has devastated trees across Massachusetts over the past few years.Minnesota Department of Natural Resources/AP/File

Most arrive as stowaways on the wooden pallets and crates that help transport some 25 million shipping containers into the United States each year.

The invasive forest pests are ravaging woods and urban canopy across the country, costing property owners and communities, especially in the Northeast, billions a year, according to a study released Tuesday by the journal Ecological Applications.

The steady march across the continent of the emerald ash borer, Asian longhorned beetle, hemlock wooly adelgid, and other non-native insects has been wreaking havoc that requires urgent solutions, said the authors of the study, which they described as the most comprehensive review of forest pests conducted in the United States.


The pests, which also enter the country on plants that are destined for nurseries, have taken an especially harsh toll on trees in Massachusetts, which is home to 57 types of pests, more than every other state except New York and Pennsylvania.

“The introductions of invasive pests that we continue to have is unacceptable,” said Dave Orwig, a forest ecologist at Harvard Forest in Petersham and one of 16 authors of the paper. “We’re just not doing enough.”

There are more than 400 forest pests in the country, and every state is affected. Louisiana has the fewest, with 12, while New York has the most, with 62.

Despite federal efforts to prevent their entry, such as having ports spray pallets with pesticides, between two and three new forest pests, on average, arrive in the country each year, Orwig said.

In Massachusetts, the pests include winter moths, which have devastated forests in the eastern part of the state; oak crypt gall wasps, which have been killing black oaks to the south and on the islands; and a range of others, including the emerald ash borer, which has killed billions of dollars worth of ash trees nationally and was first found in Massachusetts in the Berkshires town of Dalton in 2012.


Many of the state’s hemlock trees have fallen prey to a small insect called hemlock wooly adelgid, while Asian longhorned beetles have devastated red maples, especially in Worcester, where authorities have removed more than 34,000 trees at a cost of about $150 million, Orwig said.

“It looked like a hurricane had struck the city,” he said of Worcester. “It will take decades or more for the community to recover the benefits of the trees.”

The state’s trees have also suffered from a range of pathogens, including butternut canker, dogwood anthracnose, Dutch elm disease, and beech bark disease.

Conservationists who reviewed the study said its estimate for the financial toll of the pests may be too conservative. The authors are also probably underestimating the costs of their recommendations to address the problems, they said.

“If you raise the costs of trade, you also have consequences of lost public welfare, and a lost value of the trade,” said Frank Lowenstein, deputy director of New England Forestry Foundation, a conservation group in Littleton.

But he agreed the United States should be doing more to protect its forests.

“Trees are vital to our air quality, water quality, and the stability of our climate,” he said. “They’re the foundation of life in New England.”

The study estimated that 63 percent of US forestland — some 825 million acres — is at risk of increased damage from existing pests. The insects have already eliminated nearly all the American chestnuts from the nation’s forests, and all the American elms from cities. Some pests can decimate an entire tree species within a few decades.


Reducing the pest population would provide substantial economic benefits, the study found. It recommended that ports and shipping companies ban the use of wood packing materials, including pallets and large spools, which often harbor the pests. Instead, they should use alternatives, such as plywood, strand lumber, and other non-solid-wood packaging.

The study also called for restrictions on live woody plants being allowed into the country, and increased penalties for those caught bringing in invasive pests or violating other rules.

“We need to act now to strengthen prevention if we are going to protect billions of valuable trees,” said Gary Lovett, a forest ecologist at the Cary Institute of Ecosystem Studies in New York, and the paper’s lead author.

The use of wood packing materials at ports is a major factor in the unintentional importation of pests.
The use of wood packing materials at ports is a major factor in the unintentional importation of pests.David L. Ryan/Globe Staff/File

David Abel can be reached at dabel@globe.com. Follow him on Twitter @davabel.