Changing climate, changing forest zones

Issue: Climate change is expected to alter the distribution of tree species in Canada, adding a level of uncertainty to forest management and planning.

Solution: New species zones are being mapped and new models developed to help decision-makers predict how forests may shift in response to climate change.

A stand of sugar maples growing near Hudson Bay is a logic-defying image for most Canadians. Yet depending on the pace of climate change, the reaction of different tree species and a host of other factors, such a landscape may not be far-fetched by the middle or end of the century.

Climate change is expected to redraw the lines within which trees and other plants grow across the country. How quickly that redrawing will occur, where it will take place and which species will be affected are still unknown. But Canadian scientists are hoping to provide insight into how best to plan for climate change and its effects on forest zones.

Mapping plant ranges

Under most climate change scenarios, whether conservative or radical, growing environments are likely to change, making it hard to keep traditional plant hardiness zones up to date.

With this in mind, researchers with the Canadian Forest Service (CFS) have begun a project that’s intended to go beyond a single general map that shows plant hardiness zones to individual maps for each plant species that show the possible range of that species across Canada and the United States. Plant experts and members of the public are asked to report which species exist at their location. Once there’s enough data for a species, a range map is created and updated regularly as more information is submitted. To date, almost 3,000 species have been modelled.

Besides providing more accurate detail on where individual species actually grow, this new approach to mapping plant ranges will make it easier to track the effects of climate change on individual species over large areas.

For more information and sample maps, see Canada’s Plant Hardiness website.

Aspen dieback, Saskatchewan parkland, August 2004

Aspen dieback, Saskatchewan parkland
August 2004. Photo: Michael Michaelian, CFS

Tracking the effects of climate change on aspen

Trembling aspen, the most common deciduous tree in Canada’s boreal forest, is valuable from both an ecological and a commercial standpoint. Since the 1980s aspen have been suffering from dieback and periods of slow growth, especially along the southern edge of the boreal forest. Defoliation by insects is one cause; severe drought is another.

In 2000 CFS began a long-term study of the effects of climate change on aspen in the western boreal forest. The CIPHA study (short for “Climate Change Impacts on the Productivity and Health of Aspen”) is monitoring the growth and general health of aspen in areas considered sensitive to changes in climate.

The project’s laboratory is huge: a system of long-term research plots extending from the Northwest Territories and northeastern B.C. across the Prairie provinces to northeastern Ontario. And the goals are ambitious: to detect climate change impacts as early as possible and to predict what the future has in store for the health and productivity of this species. The latter aspect of the project will particularly benefit forest managers who need guidance on how aspen will fare under different climate scenarios.

A study as large and as long as CIPHA requires cooperation on many fronts. CFS researchers work with climate modellers and researchers from Environment Canada and Canadian universities. CIPHA has received financial support from various sources, and its work is continuing in collaboration with the Alberta government and other agencies.

Modelling the impacts of climate change

Forest managers need to be able to factor the effects of climate change into their planning. To help with this process, researchers at the University of British Columbia have expanded FORECAST, their forest management decision-support tool, to include climate change capabilities. Now forest managers can use the computer model to examine how different climate change scenarios might affect their ability to meet various forest management objectives, such as maintaining stand productivity and features important for wildlife habitat.

“Clearly, our work is a relatively simple first step at exploring some of the potential responses of forests to a changing climate. Given the highly complex nature of this issue, and the many uncertainties involved, efforts to respond to climate change will no doubt be best served by an adaptive management approach that is sensitive to new information gained from ongoing monitoring efforts. The plant hardiness project gives us a mechanism to make use of monitoring efforts and continue to update results.”

—Dr. Daniel McKenney, Chief of Landscape Analysis and Applications,
Canadian Forest Service