A mountain pine beetle tethered to a “flight mill” in the lab of Maya Evenden (University of Alberta) to learn how far they can fly. The answer: one to four miles, depending on their age. The record was 15 miles. Photo by Peter Essick/National Geographic.

According to an article appearing in the April 2015 issue of National Geographic, more than 60 million acres of forest — from northern New Mexico through British Columbia — have suffered die-offs since the 1990s due to the spread of the mountain pine beetle (Dendroctonus ponderosae).

The beetles bore through the bark and create tunnels beneath it, where the females lay eggs. When the eggs hatch, the larvae feed on the bark as well.

But it gets worse. The beetles are fungus farmers that carry spores on their bodies. When they tunnel under the bark, the spores grow, providing an excellent food source for pine beetle larvae — but it simultaneously damages the trees, including lodgepoles, ponderosas, white pines, jack pines, and others.

In order to stop the beetle’s spread, infected trees must be removed. The following video shows Canadian forest health officers at work as they battle the beetle.

Scientists blame years of drought, which weakens trees’ natural defense systems, as well as warmer temperatures and a lack of forest fires, which means more trees on the same amount of land. That causes competition among the trees for water and nutrients, and further weakens their defenses. As this article from the Journal of Integrated Pest Management concluded, one of the keys to managing bark beetles involves adequate spacing between host trees.

“For its current good fortune, the mountain pine beetle can thank us,” according to the NG article. “To start with, we’ve spent the past century eliminating forest fires — thereby turning the woods into beetle buffets. When the crisis began, British Columbia’s forests were packed with three times as many mature pines as there would have been had they been allowed to burn naturally. Like mountain pine beetles, fire is native to western forests, and it’s as important as rain to their health. It nourishes soil, spreads seeds, creates openings for sunlight, ensures habitat for all sorts of creatures.”

Click here for the full article from National Geographic.