When you think of deforestation, you might conjure up images of loud and heavy machinery bulldozing 200-year-old trees, or rampant forest fires turning trunks and branches black with ash. But there’s another killer out there, and it’s small enough to fit in the palm of your hand. Tree-killing insects are responsible for large-scale deforestation across North America. 

While some insects work by defoliating and weakening healthy trees, others, like bark beetles, target trees that are already sick or under stress. According to the Food and Agriculture Organization of the United Nations, 35 million hectares of forest are damaged by tree-killing insects each year!

The Mountain Pine Beetle

Native to North America’s west coast, the mountain pine beetle has devastated forests from British Columbia to Mexico. No larger than a grain of rice, the invasive insects fly from tree to tree, weakening and killing species like lodgepole, western white, sugar, whitebark, and limber pines by boring into the bark. These boring holes, known as “pitch tubes” are tell-tale signs of a mountain pine beetle infestation. Piles of dark dust, known as boring dust, may also be found around the base of the tree. Large populations of mountain pine beetles can be determined by the presence of woodpeckers, which feed on developing larvae under the bark, punching holes into thin-barked trees like the whitebark pine. Within eight to 10 months of  a successful attack, the tree will fade and eventually die. Here's a look at a pine beetle infested forest from above. 

According to the U.S. Forest Service, more than 1.5 million acres of forest in northern Colorado and southern Wyoming are affected by the mountain pine beetle epidemic, which was triggered by an extended drought in the late 1990s and early 2000s. 

"By about 2012, beetles will have killed nearly all of the mature lodgepole trees in northern Colorado and southern Wyoming.  Besides affecting watersheds, future timber production, wildlife habitat, recreation sites, transmission lines, and scenic views, beetle-killed trees also present a fuels build-up situation that could result in catastrophic wildland fires."

The Emerald Ash Borer

The Effects of Climate Change

Insect outbreaks are a normal part of a forest’s biological cycle. In fact, by eliminating dead or sick trees, insect infestations can encourage a more productive ecosystem and healthier forest. Rampant and recurring outbreaks, however, are more than just natural disturbances; they can have long-lasting or even irreversible effects on forests and ecosystems. The reason for these outbreaks is in large part caused by climate change. 

Warmer, drier seasons contribute to environments ideal for travel, mating, and survival among tree-killing insects. As temperatures increase, tree-killing insects are moving into forests previously untouched by invasive species. Leaves, needles, and bark shed as a result of damage caused by insects also increase the risk of forest fires. These changes not only affect trees, but entire ecosystems that surround and rely on them.

How Can I Help Stop the Spread of Invasive Species?

There are many things you can do as an individual or community to reduce the spread of tree-killing insects. Here are just a few:

1. Refrain from moving firewood from one location to another.
2. Report sightings of invasive or unfamiliar species.
3. Plant trees and plants native to your area.
4. Refrain from moving organic matter like wood, flowers, or plants across borders.
5. Stay on designated pathways and trails.
6. Wash your boots of seeds and plant matter after hiking.

References: 1, 2, 3, 4, 5, 6, 7