Cold Snap Kills Mountain Pine Beetle: Canadian Forests’ Littlest Big Threat

The population of the destructive mountain pine beetle in Alberta was greatly reduced during a cold snap that hit the province mid-January. Nightly temperatures of around -35°C were maintained for over a week (1). During this time, as much as 95% of the population was killed in some areas (1). This is good news – the mountain pine beetle is an invasive species that burrows in pine tree bark and threatens their survival (2). It is native to the Rocky Mountain Ecosystem in British Columbia and studies suggest that outbreaks within this range have occurred for centuries (3). However, it appears that a warmer climate is providing the conditions for the beetle to move past its native territory, threatening large portions of Western Canada’s boreal forests (1). This outbreak is causing alarm about the destruction of forests, which act as carbon stores, and the unsustainability of methods used to fight mountain pine beetle outbreaks.

The current infestation has been active since the 1990s in British Columbia (4). The beetle has now moved beyond their historic range and into the boreal forest of Alberta, where they have spread at an average rate of 80 km/year and into Saskatchewan’s South West (4). Decades of successful fire suppression in Canada’s forests has led to older and weaker pine stands that are more susceptible to attacks and create a path for the beetles to move through (5). In addition, climate change has caused the consistently favorable weather conditions of warm and dry summers, and mild winters. This has allowed the beetles to move into the higher elevations of the boreal forest (3). The scale of the beetles’ impact grows with rising temperatures because the population increases and the beetles are able to disperse farther, more than 100 km, when weather conditions are favorable (4).

During the current outbreak there has been unprecedented damage to Canada’s forests, with more than 18 million hectares of forest affected. In addition, huge sums of federal and provincial funds have been put towards managing the outbreak: $484 million from 2004 to 2016 (6). Frustratingly, the outbreak also hurt Canada’s carbon budget. A 2008 study in Nature highlighted the immense contributions of the beetle outbreak to Canada’s emissions – damage to trees limits the ability of forests to store carbon, and decay of dead trees leads to production of carbon dioxide and methane (7). At their worst, beetle outbreaks contribute to emissions at nearly the same scale as annual forest fires (7). In addition to the tree mortality caused by the beetles, accepted management strategies include clear-cutting infected trees, and harvesting swaths of forest ahead of the beetles’ path (8).

In conclusion, climate change-induced warm and mild weather and successful fire suppression tactics in recent years have created the conditions for the mountain pine beetle to move beyond its historic range, cause unprecedented destruction, and increase carbon emissions. The recent cold snap in Alberta drastically reduced the beetles’ population and will likely slow its expansion, as, luckily, it hit especially hard in regions where the mountain pine beetle is of most concern (1). These reductions will inform the year’s management strategies, provide some relief to Alberta’s forest and those who enjoy them, and remind us to be thankful for Canada’s cold winters (1).