Mountain Pine Beetles: Disaster for America’s Grizzlies?

Few animals are as revered by Americans as the grizzly bear. With its lumbering posture, powerful stature, and resourceful nature, the grizzly bear is a mammalian manifestation of the landscapes it inhabits. Historically, the North American grizzly bear lived across much of Alaska, Canada, western and central United States, and into Mexico, and was one of the most widely distributed animals across the continent. Currently, large populations are found in Alaska and Canada, and are making a comeback in the US lower 48, most notably in the greater Yellowstone ecosystem.

There are talks of upgrading the Yellowstone grizzly bear from its threatened status, but climate change poses a threat to conservation efforts. Food sources and associated ecosystem functions are being influenced—most notable is the degradation of whitebark pine ecosystems by mountain pine beetles, jeopardizing crucial grizzly bear food sources. These changes may cause the bears to deviate from historic life cycles, marginalizing individual fitness levels and negatively impacting population levels.

Due to fire suppression and milder winters, mountain pine beetles are beginning to infest and destroy whitebark pine populations. Killing a mountain pine beetle requires five days of sustained temperatures below -30° Fahrenheit, and stretches of cold weather are becoming less frequent. Whitebark pine also relies on fire to propagate, as it establishes quickly in post-fire areas. As wildfire suppression remains key to keeping human populations safe and happy, and as winters continue to grow milder, grizzly bears face a sizable hurdle as they adjust to changes in critical habitats and food sources. Removing the Yellowstone ecosystem grizzly bear population from the Endangered Species List would likely be premature as the world’s climate continues to change.

by Brendan O’Callaghan