Taiga Plains Ecozone

Changing Forest Landscape Conditions

Overall, the forests of this ecozone are considered healthy. Insect and disease outbreaks are common but are essential to the ecological integrity of these forests. Spruce budworm is the most widespread, being concentrated in white spruce stands along rivers, particularly the Mackenzie, Nahanni, and Liard rivers. Since 1989, outbreaks have covered between 100 000 to 400 000 ha annually.

Range extension of forest tent caterpillar: Of interest is the recent outbreak, between 1995 and 1997, of forest tent caterpillar in the Liard River valley (Brandt et al. 1996, Brandt 1997). It was the first documented outbreak of the insect this far north. At its peak in 1996, the outbreak covered 225 000 ha of trembling aspen forests, resulting in moderate to severe defoliation. One hypothesis for this occurrence is that recent warming in the region has been favorable for insect growth and reproduction (J. Brandt, Canadian Forest Service, personal communication).

Changing Biodiversity

The overall biodiversity within these forests is not threatened. The forest wetland ecosystems of the Taiga Plains are particularly important as they are essential to the survival of many North American migratory species, including lesser snow geese, trumpeter swan, Caspian tern, and lesser yellowlegs (Alexander et al. 1991).

Changing Atmospheric Environment

Potential climate change impacts: The impact of climate change on these forests is a priority area of research. The Mackenzie Basin Impact Study (MBIS), a collaborative research program initiated in 1990 and completed in 1996, concentrated on such potential impacts within the Mackenzie River watershed. Results indicate that a warming climate would cause various impacts, including lower water levels, less permafrost, longer growing seasons, increased fire frequency, increased incidence of insect infestations, and less caribou habitat (Cohen 1997).

Other studies within the Mackenzie River Basin suggest that, with warming temperatures, the white pine weevil would extend its natural range northwards and upward in elevation. A warming of 3ºC would increase the area of high hazard for this insect from 24 to 75% of the commercial forest within the Basin (Sieben et al. 1997). White pine weevil attacks spruce and pine species throughout North America, causing reduced growth and wood quality.

There has been a northward shift of the permafrost boundary by 140 km in Alberta, Saskatchewan, and Manitoba due to general warming conditions over the last 200 years (Halsey et al. 1995). Under current projections of climate warming, this northward retreat of the permafrost line would be accelerated. Overall warming may result in enhanced growth and productivity of these northern forest ecosystems. However, permafrost is also important to the survival of many of these northern ecosystems. It elevates surface soils, allowing trees to survive because their roots remain relatively dry (Zoltai 1993, Vitt et al. 1994). In the absence of permafrost, previously elevated, dry forest soils may become saturated with water, resulting in reduced growth and increased mortality of existing stands.

From research carried out within this ecozone, changing weather patterns are known to have direct and indirect impacts on boreal insects. A changing climate disrupts the life cycle of insects. Indirectly, it impacts on hosts, predators, and competitors (Fleming and Volney 1995). Changes in the timing of flushes of biting insects could adversely affect the breeding success of boreal nesting songbirds and the migratory movements of many other birds (Herrington et al. 1997; Environment Canada 1996).