Science Features

Forest Pests: Boring a Hole in Your Wallet

“These pests are clearly expensive, and the costs we’ve calculated only represent the lower bound.” —Juliann Aukema

By Darci Palmquist

Forest pests such as the Asian longhorned beetle and emerald ash borer are doing massive damage to trees and forests in the United States—but how much is that damage costing, and who’s largely footing the bill?

You are, according to a new study funded by The Nature Conservancy.

The study, just published in the online journal PLoS ONE, found that local communities—in the form of homeowners and municipal governments—are bearing the largest cost burden of invasive forest pests.

These annual costs include:

  • $2 billion in local government expenditures for tree damage and removal; 
  • $1.5 billion in lost residential property values;
  • $216 million in federal government expenditures on management and regulation.

“What’s surprising is how the economic impact of these insects is being felt largely at the urban and suburban level,” explains Juliann Aukema, the study’s lead author and a scientist with UC-Santa Barbara’s National Center for Ecological Analysis and Synthesis (NCEAS).

“I expected a larger cost to federal agencies and other owners of large forest lands.”

Which means these pests aren’t just a problem facing remote forest wilderness areas. Chances are, you are or will soon be contending with them in your own backyard or neighborhood.

“Imagine living on a beautiful, shady tree-lined street one day, and a stark, tree-less street the next,” says Bill Toomey, director of forest health protection for the Conservancy.

“In places like Worcester, Massachusetts, that’s a very real impact the residents are dealing with as a result of an Asian longhorned beetle outbreak.”

Why Are Forest Pests Such an Economic Problem?

Like termites chewing apart a home, invasive insects such as the Asian longhorned beetle and emerald ash borer (EAB) are quickly and systematically destroying forests across the United States.

“Wood borers especially can kill trees quickly, and they spread rapidly,” explains Aukema. “This makes them far more damaging than something like the gypsy moth, which might defoliate a tree several times before actually killing it.”

And the reach of the damage is surprisingly far. Many wood products—such as flooring, furniture, tool handles and baseball bats—are made from ash trees, which Aukema says are in real trouble in the United States.

“We’re looking at the potential loss of ash trees, just like we functionally lost the American chestnut to chestnut blight,” says Aukema.

Solving the Problem: An Ounce of Prevention Goes a Long Way

Aukema adds that the study’s estimates don’t even include how destruction from forest pests might impact U.S. air and water quality, climate regulation, wildlife habitat and more.

“These pests are clearly expensive, and the costs we’ve calculated only represent the lower bound,” says Aukema. “Our best bet is to keep them out in the first place.”

The researchers estimate there’s a 32% chance that another highly destructive borer species will invade the United States in the next 10 years at current introduction rates or if introduction rates don’t change, which makes addressing the problem at the source even more urgent.

What can be done? Global trade is the primary cause of introduced pests, so solving the problem of keeping these pests out lies primarily at the federal level.

“Wood packaging is one of the main avenues of entry for these pests,” says Toomey. He and other Conservancy staffers are working with the USDA to help strengthen trade regulations to make them more effective at keeping pests out in the first place. 

But average citizens can also play a key role.

Since the emerald ash borer can travel only short distances on its own, scientists suspect the beetle is spreading so far and wide because businesses and average citizens unknowingly move it in firewood, logs and nursery trees.

Here’s how you can help:

  1. Be a citizen scientist! Monitor your trees and plants and report back any unusual findings to your state agriculture agency
  2. Don’t move firewood. Moving firewood from one place to another can spread invasive species to non-infected forests. 
  3. Get involved in your community’s local tree planting efforts and become a steward of local trees and urban forests.

About the Science: How Was the Study Done?

Researchers developed a sophisticated modeling technique that assessed the costs of 3 major types of invasive forest pests across different economic sectors, including the federal government, municipal governments, homeowners and forest landowners. Their unique approach included close and early collaboration between ecologists and economists.

“In addition to the results we reported in this study, the methods we developed can be used widely,” says Aukema.

For instance, she explains, with just 3 key pieces of data in hand a scientist could use this model to estimate the cost impacts of other types of invasive animals or plants either in the United States or other countries, as well as the cost impacts of natural events such as hurricanes and wildfires.

Looking Ahead

Aukema et. al.’s study is one of many that have emerged from a series of working groups comprised of scientists and policy experts from the Conservancy, universities and government agencies to better understand the economic and ecological impacts of forest pests.

So far 12 studies have been published and more will be out in the coming years. Together, they aim to help policy makers make better decisions about regulation and management of invasive forest pests.


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