When Gary Lovett was studying the effect of acid rain in New York’s Catskill Mountains 20 years ago, he ended the experiment early because so many trees in the test plots were dying — not from acid rain, but from attacks by forest pests.

“I consider air pollution and climate change to be serious, long-term threats to the forests,” said Lovett, senior scientist at the Cary Institute of Ecosystem Studies in the Hudson Valley. “But neither of those is changing the forest the way the pests are.”

In a study published this month in the journal Ecological Applications, Lovett and 15 colleagues estimated that 63 percent of U.S. forest land, or about 825 million acres, is at risk of increased damage from established pests, and new pests continue to arrive with cargo shipments from overseas.

There are more than 400 forest pests in the country with every state affected, Lovett said. New York has the most, with 62 types of pest. The Northeast and upper Midwest are the most heavily infested regions. Lovett said that’s because of centuries of overseas trade from regions where tree species are similar but have evolved with insect pest resistance that U.S. trees lack.

Imported tree pests long ago wiped out eastern chestnuts and elms. Now under siege are hemlocks, ash, beech, oaks, maples and dogwood. Imported forest pests cause more than $2 billion in damage each year, with communities and homeowners bearing the greatest cost because of the expense of removing and replanting trees that take decades to mature.

From ABC News: https://abcnews.go.com/Technology/wireStory/imported-forest-pests-billion-damage-annually-39159645