Thinking about the sustainability of carbon sequestration in forests

Bugs are one of the most common killers of trees, their common names associated with the tree they attack- Douglas Fir Tussock Moth, Emerald Ash Borer, Spruce Budworm, White Pine Weevil. The mountain pine beetle is similar in name, but was first known to a few households as the carrier of blue-stain fungi, creator of the elegantly-stained boards popular during the 1970s and 80s for interior paneling and woodwork. As a pest, the mountain pine beetle didn’t reach the national stage until the 1980s, when large-scale infestations began killing entire stands of trees. Today, the beetle is known for the deaths of large swaths of forest across the Rockies, especially in Colorado, Wyoming, Montana, and British Columbia. Sometimes, these forests burn, as happened in 2009 when over 600,000 acres of partially-beetle-killed-timber burned in British Columbia, leading to thousands of evacuations and highway closures the province and neighboring Alberta (where I was bicycling at the time). Other times the forests are clear-cut before either the bug or fire hits, and often the entire forest just slowly decomposes. The situation is so dire in many areas that entire government departments are now dedicated to the beetle; the state of Montana and the province of Alberta even have web prefixes, beetles.mt.gov and mpb.alberta.ca, to address the spread of bark beetles. Today western forests, according to Warner Kurz’s study in Nature, are reversing their trend as carbon sinks and are releasing more carbon than they originally took in. Pines, like other plants, breathe carbon dioxide, the very gas that warms our planet now. So anything that absorbs carbon is generally a good thing, but too much of a good thing, in the case of pines, can turn into a potentially very bad thing. In British Columbia and the rest of Rockies, there now exists a positive feedback loop contributing to global warming. The mountain pine beetle benefits from warming climates and can move to higher altitudes and latitudes because of warmer winters. The mountain pine beetle can expand terrain as its victims contribute more CO₂ to the atmosphere and contribute global warming, which then helps the mountain pine beetle. It has been estimated that 7.5% of Canada’s CO₂ emissions come from British Columbia forests, and that by 2020 990 megatons of CO₂ will have been released by the forests. This transition of forests from carbon sinks to carbon emitters is problematic for life as a whole. In 2008, the Natural Resources Defense Council filed an endangered species listing for the Whitebark Pine, a relative of the Ponderosa common at elevations around 6000 feet. A June 2011 decision by the US Fish and Wildlife Service denied the listing, but the Whitebark Pine was found to be at risk due to climate change exacerbating existing threats, including the bark beetle. The US government at last recognized the connection between global warming and bark beetles. Mountain pine beetles are also not the only insects aided by global warming, and when forests are planted or replanted, as suggested as an easy way to sequester or contain CO₂, the even age distribution of trees will make the forests once again vulnerable to infestation. In this larger scale, the mountain pine beetle is just one of thousands of players, all of which have the power to turn forests from sinks into emitters of CO₂. While there is no obvious solution to global warming, the pine bark beetle is a reminder that sequestering all of our carbon into forests may be an evil rather than a good, and a plea to the world to think beyond the storage of carbon.