More trees are dying in Northeastern forests, and not just from old age. A new study authored by researchers at the University of Vermont finds disease and invasive insects spurred on by climate change are increasingly changing the character of the region’s woods.
“It’s definitely worrisome,” said Lucas Harris, a postdoctoral researcher at the Rubenstein School who was the lead author on the study. “It’s not just that scattered trees are dying here and there in stands.”
The researchers used the federal Forest Inventory and Analysis database to compare more than 300,000 records of tree death across 18 states from 2009 to 2024.
At the start of that period, logging was the leading cause of tree death in the Northeast. But during that time, losses from natural causes increased by nearly 40%.
“It’s definitely worrisome. It’s not just that scattered trees are dying here and there in stands.”Lucas Harris, postdoctoral researcher at the Rubenstein School
For roughly half of these losses, researchers don’t know what’s driving the shift. But insects now account for almost a quarter of tree deaths in the region. Disease is also a growing contributor.
Extreme weather was also a major factor, and one researchers expect will play a growing role.
Coauthor Tony D’Amato says climate change piles onto all these other stressors.
“For a long time, we’ve assumed 1-2% of the trees in the forest die every year from natural causes,” D’Amato said. “[Outside of that] tree harvesting is often the biggest cause we’re seeing. But now we’re getting into a phase with all these novel stressors, like emerald ash borer, hemlock woolly adelgid, beech leaf disease, extreme precipitation, events like droughts, too much wind and rain, that those are all coming together to generate higher levels of mortality than we’re used to here.”
Climate change can create favorable conditions for invasive pests like the emerald ash borer, as winters become milder and easier to survive for many insects, and warmer shoulder seasons make it easier for them to reproduce.
It can also throw delicate relationships out of whack, allowing species that didn’t previously threaten tree health to see a boom in population.
“This threatens what has been a pretty reliable place to have trees that are healthy and growing. We’re now seeing a pretty rapid change in that.”Tony D'Amato, University of Vermont researcher
A warming climate with volatile weather also stresses trees, making it harder for them to recover after being defoliated or having their bark compromised.
The researchers found that tree loss from timber harvests stayed relatively stable in all the states they studied over the last 15 years.
Tree deaths by natural causes now surpass timber harvests in every state in the region except for Maine and Virginia. Insects alone caused more deaths than timber harvests in Connecticut, Massachusetts, New Jersey and Rhode Island.
States to the south and west of Vermont, particularly southern New England, saw the largest increases in tree mortality from natural causes.
D’Amato says this should be a warning to land managers in northern New England that forests here are likely to soon face many of the pressures they’re seeing down south.
He says the regional timber industry could see impacts, as could tourism. But these trends also have cultural ramifications in the region.
He offered the example of the black ash tree, which is declining across the study area and is central to Abenaki and Haudenosaunee stories, culture and art.
“This threatens what has been a pretty reliable place to have trees that are healthy and growing,” he said. “We’re now seeing a pretty rapid change in that.”
