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article imageAn expanding army of insects is eating away at U.S. forests

By Karen Graham     Dec 7, 2016 in Environment
Insects, both native and those brought into the country, are draining the life out of the nation's forests. Global trade, a warming climate, and drought-damaged trees have helped insects to become one of the greatest threats to biodiversity in the U.S.
The Hemlock woolly adelgid is just one of a growing number of insects draining the life out of forests from New England to the West Coast of the United States.
Scientists say insects are already driving some tree species to extinction and causing billions of dollars a year in damages — and the problem is expected to only get worse. "They are one of the few things that can actually eliminate a forest tree species in pretty short order — within years," said Harvard University ecologist David Orwig, according to the Associated Press.
Ecological Applications
A peer-reviewed study this year in Ecological Applications explains that the insect scourge is expected to put 63 percent of U.S. forests at risk through 2027, particularly in the Northeast and Upper Midwest. It will cost several billion dollars annually for dead tree removal, not to mention declining property values and losses to the timber industry.
The study focused on non-native forest insects and diseases in the U.S. and their ecological and economic impacts, how they arrived, their distribution within the country, and options for reducing future invasions.
How do non-native pests arrive in the U.S.?
The study points out that invasive insects gain entry into the country through two major pathways — the importation of plants and in wood packing material such as pallets and crates. "The primary driver of the invasive pest problem is globalization, which includes increased trade and travel," said Andrew Liebhold, a Forest Service research entomologist in West Virginia.
Emerald Ash Borer (adults) and tree damage from larvae.
Photo source: US Forest Service  David Cappa...
Emerald Ash Borer (adults) and tree damage from larvae. Photo source: US Forest Service, David Cappaert, photographer.
Liebhold says climate change is also playing a role in the spread of non-native and native insects. "As climates warm, species are able to survive and thrive in more northerly areas."
In February 2015, Digital Journal reported on the earlier emergence of the black-legged tick, a carrier of Lyme disease, with other species expanding their geographical range because of a warming climate.
In 2011, the U.S. Forest Service issued its first "report card" on the health of the nation's forest in over eight years. At that time, the agency said the nation's 751 million acres of forestland had remained "remarkably stable" over the past half-century, despite insect damage and losses due to drought and fires, according to NBC News.
Female gypsy moths laying their egg masses on a tree.
Female gypsy moths laying their egg masses on a tree.
Screen grab
Rob Mangold, the agency's director of forest health protection said, "Forests go through this cycle of death to produce a new forest. You have to look at things in the long-term, although locally there are some really big impacts."
But since 2011, and the report that looked at the period covering 2003 to 2007, things have drastically changed, not only in our forests but with our climate. The western part of the country has been in a severe and prolonged drought, and warming temperatures have started impacting our environment.
From emerald ash borers, first found in Michigan in 2002, and the gypsy moth, discovered in 1869 in Boston, to our native bark beetles taking advantage of a warming climate and a prolonged Western drought to quickly spread from Mexico to Canada, our forests are being rapidly devoured.
The brown spruce longhorn beetle is an invasive insect from Europe that is now found in Canada and t...
The brown spruce longhorn beetle is an invasive insect from Europe that is now found in Canada and the U.S. It is known as a secondary forest insect, attacking trees that have already been subjected to other types of insect attack or environmental stresses.
Natural Resources Canada
And it's not just our forests we should be very concerned about — it's our urban forests, too. In 2008, Worcester, Massachusetts had to remove 31,000 trees because of an Asian long-horned beetle infestation. The study points out that while many insect names are familiar to most of us, there are many more recent arrivals, and the current and potential impacts can be severe.
Policies have not worked to curb the importation of invasive bugs
According to the study, "Despite a succession of policies beginning in the early 20th century to reduce the introduction of these pests, the rate of establishment has continued unabated in the face of increasing trade."
Not only are our policies not working as expected, we are going to be inundated with even more non-native pests as global trade continues to expand, bringing pests into this country we have never had to deal with before. The continued influx of invasive pests represents a severe risk to United States forests and urban and suburban landscapes.
California's drought crisis has caused wildfires  decimated forests  threatened animal species ...
California's drought crisis has caused wildfires, decimated forests, threatened animal species and deprived thousands of homes of access to clean water
Justin Sullivan, Getty Images/AFP/File
The study authors suggest we need to have stricter enforcement of regulations regarding the import of horticultural plants, or going further, ban them outright. We also need to educate travelers about the risks of bringing live plants into the U.S. and enforce compliance with the regulations now in place.
It's a complicated dance to get all the agencies involved with our trade, customs and the various agencies mandated with protecting our well-being, health and safety on the same track. It won't be an easy fix, and that is a given. But we do have to do something while we still have the time and opportunity to fix the problem.
More about Global trade, Climate change, droughtweakened trees, native insects, invasive insects
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