Canadian Forest Service Publications
Anticipating the consequences of climate change for Canada's boreal forest ecosystems. 2013. Price, D.T.; Alfaro, R.I.; Brown, K.J.; Flannigan, M.D.; Fleming, R.A.; Hogg, E.H.; Girardin, M.P.; Lakusta, T.; Johnston, M.; McKenney, D.W.; Pedlar, J.H.; Stratton, T.; Sturrock, R.N.; Thompson, I.D.; Trofymow, J.A.; Venier, L.A. Environmental Reviews 21(4):322-365.
Issued by: Northern Forestry Centre
Catalog ID: 35306
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Canadian boreal woodlands and forests cover approximately 3.09 × 106 km2, located within a larger boreal zone characterized by cool summers and long cold winters. Warming since the 1850s, increases in annual mean temperature of at least 2 °C between 2000 and 2050 are highly probable. Annual mean temperatures across the Canadian boreal zone could be 4–5 °C warmer than today’s by 2100. All aspects of boreal forest ecosystem function are likely to be affected. Further, several potential “tipping elements” — where exposure to increasing changes in climate may trigger distinct shifts in ecosystem state — can be identified across the Canadian boreal zone. Approximately 40% of the forested area is underlain by permafrost, some of which is already degrading irreversibly, triggering a process of forest decline and re-establishment lasting several decades, while also releasing significant quantities of greenhouse gases that will amplify the future global warming trend. Warmer temperatures coupled with significant changes in the distribution and timing of annual precipitation are likely to cause serious tree-killing droughts in the west; east of the Great Lakes, however, where precipitation is generally nonlimiting, warming coupled with increasing atmospheric carbon dioxide may stimulate higher forest productivity. Large wildfires, which can cause serious economic losses, are expected to become more frequent, but increases in mean annual area burned will be relatively gradual. The most immediate threats could come from endemic forest insect pests that have the potential for population outbreaks in response to relatively small temperature increases. Quantifying the multiple effects of climate change will be challenging, particularly because there are great uncertainties attached to possible interactions among them, as well as with other land-use pressures. Considerable ingenuity will be needed from forest managers and scientists to address the formidable challenges posed by climate change to boreal ecosystems and develop effective strategies to adapt sustainable forest management practices to the impending changes.
Plain Language Summary
This paper examines several approaching threats of climate change to Canada’s boreal ecosystems up to 2100. The resilience limits of presently stable ecosystems will be increasingly challenged if projected changes in climate unfold. This could result in permanent changes in those ecosystems. Warming, drying, and increased carbon dioxide concentration may stimulate forest growth in some regions, but this benefit would likely be outweighed by the combined effects of increasingly serious droughts, more intense storms, and wildfires. Of particular concern is that about 40% of Canada’s boreal forests grow on permafrost soils, which have been warming since the 1850s. Permafrost thawing has increased markedly since the 1970s and will likely further accelerate, causing irreversible changes to large areas of northern forests and adding large amounts of greenhouse gases to the atmosphere. Catastrophic outbreaks of forest insect pests are less certain but could be triggered by relatively small temperature increases. There will be major northward shifts in the climate zones suitable for boreal forests, adding further stresses on growth and regeneration. In combination, these threats seem likely to drive major changes in all boreal forest ecosystems, but particularly along the southern boreal fringe in western Canada. The changes will create new unprecedented challenges for forest researchers, managers, and policy-makers.