When we burn dirty sources of energy like coal and oil, we release carbon pollution into the atmosphere. Thankfully, some of the pollution is taken up by carbon “sinks” — ecosystems like oceans and grasslands that store carbon and temporarily keep it from warming the atmosphere.
A new study estimates that between 1990 and 2007, the world’s established forests stored about a third of the carbon from dirty fuels. But forests need to be healthy to hang onto their stored carbon, and a little beetle is posing a big challenge to forests in western North America.
Mountain pine beetles are one of hundreds of species of bark beetles native to the U.S. and Canada. About the size of a grain of rice, mountain pine beetles burrow in the bark of live pine trees, where they lay their eggs and feed on the bark. A severe beetle outbreak has been under way for several years, creating swaths of red or gray-colored dead trees that can stretch for miles.
In British Columbia alone, the mountain pine beetle has damaged an area more than twice the size of New Brunswick, with consequences for the ability of the forests to store carbon. Another recent study found that from 1990 to 1999, Canadian forests stored more carbon than they released. But from 2000 to 2008, those same forests were a net source of carbon — largely because of beetle damage.
So mountain pine beetles may be helping warm the planet. Now here’s the other bad news: a warming planet encourages the spread of the beetles. Normally, severe, short-term freezes or sustained cold snaps help keep beetle populations in check. But as winters get warmer, beetles outbreaks are getting more severe in both the U.S. and Canada. In British Columbia, mountain pine beetles are now found in forests “previously considered climatically unsuitable.”
Some scientists wonder if jack pines in the boreal forest will be the next victim of mountain pine beetles. The beetles have already crested the Rocky Mountains into north-central Alberta, and could spread to the east if temperatures continue to climb. Boreal forests account for nearly a quarter of the carbon stored in the world’s forests — meaning without action to reduce carbon pollution, we can expect this vicious cycle of “warming-more beetles-more warming” to continue.