Photo: Forest impacts

The mountain pine beetle has killed huge swaths of forest in B.C. (Credit: joeronzio via Flickr.)

Climate change is threatening the health of forests around the world. As temperatures rise, weather patterns and the availability of water also change, altering the ability of trees to survive.

Canada's forests cover almost half of the country's landmass and make up 10 per cent of the world's forest cover. Forests are a crucial part of Canada's natural heritage, wilderness areas and economy.

Although more carbon dioxide in the atmosphere may encourage tree growth, the negative impacts of climate change are expected to far outweigh any benefits.

Forest dispersion and shifting

Although scientists predict an increase in precipitation due to climate change, it will likely not be sufficient to keep up with increased evaporation from rising summer temperatures. This will lead to decreased soil moisture, which will cause more drought-resistant trees or grasslands to displace existing forest ecosystems.

Forest fires

As hotter, drier summers increase evaporation they will also increase the risk of forest fires across most of Canada, and increase the severity of those fires. According to the government of Canada, both fire frequency in Canada's boreal forest and total area burned have increased over the last 20 to 40 years.

Rising tree lines

The alpine tree line is one of the most distinctive habitat transitions, separating continuous subalpine forest from the alpine environment.

Tree line elevation is determined by growing-season temperature. As global temperatures rise, tree lines are expected to advance upslope and northward, shrinking the alpine environment (e.g., invading alpine meadows) and fragmenting wildlife habitat. Climatologists believe that a rise in global temperatures of 3.25 degrees Celsius would be equivalent to an ecological shift upwards of about 500 metres in altitude. Alpine species confined to the tops of low-lying mountains risk extinction as the habitat is taken over by forests.


Forest disease and pest infestations

Warmer temperatures are also expected to expand the ranges and enhance the survival rates of forest pests such as the spruce budworm and the mountain pine beetle.

Infestations of the mountain pine beetle are normally controlled by intense cold snaps in the winter, but warmer winters have been one factor enabling the infestation to grow into an epidemic in British Columbia's Interior forests. Over 50% of B.C.'s commercially valuable pine timber has already been lost due to the infestation of the mountain pine beetle.

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