February 26, 1999

Canada's peatlands could crawl further north

Dr. Dennis Gignac

Most gardeners worth their green thumbs are familiar with the practice of laying peat on the garden to help preserve moisture and add beneficial nutrients to the soil. But to Dr. Dennis Gignac, peat is remarkable not only for its capacity to hold water, but also for an altogether different property - its potential for predicting the future.

A plant ecologist in the Faculté Saint-Jean, Gignac has been studying climate change and its effects on ecosystems for 15 years. His latest research focuses on peatlands (wet areas composed of dead plant matter up to six metres deep) of the Mackenzie River Basin in northern Canada, a vast part of continental western Canada running from the basin of the Athabasca River at its southern end to the Arctic in the north.

Gignac is the only researcher at the university to use climate-sensitive peatlands to predict changes in the environment. He says these plants are ideal because they respond so quickly. "By moving north or south in a peatland ecosystem today, you can see the same results as if you had waited for 20 years in one spot for the climate to change." From his model, Gignac predicts global warming could cause peatland distribution to shift northward, ultimately altering northern communities and lifestyles as we know them today.

Speaking at a seminar series on climate change sponsored by the Environmental Research and Studies Centre and funded by TransAlta Corporation, Gignac said he looked at the relationship between climate, peatland distribution and concentration of atmospheric carbon dioxide. Carbon dioxide and other trace gases normally blanket the Earth and re-radiate heat downward - hence the term "greenhouse gases"- but when they accumulate at higher than normal levels, global warming results.

By combining the data from his peatlands model with that of general circulation models (GCMs), Gignac created a snapshot of current conditions. From that he hoped to predict "what would happen if the amount of carbon dioxide in the atmosphere was doubled and therefore what would happen to other ecosystems in the Mackenzie River Basin."

He analysed 82 peatlands throughout the region for plant species, pH, height above the water table and climatic variables. From this data, Gignac segregated the peatlands into seven groups and identified "a plant indicator species" for each. To test his model for classifying peatlands correctly and placing them in the proper climatic and geographical zones, he compared his data to 100 other peatland sites and combined it with GCM data. It turns out, at current levels of carbon dioxide, his model is about 88 per cent accurate.

Gignac next calcula-ted the results for twice the level of atmospheric carbon dioxide. The results are startling: his model predicts when plants adapt to this climate, "water evaporation will increase in southern areas, permafrost will disappear in northern areas and peatland ecosystems will shift northward by about 500 km."

Based on his projections and data from a 1997 report by Stewart Cohen on the Mackenzie Basin, Gignac outlined other possible serious consequences of global warming. In the south there could be more drying, lower water levels in lakes and rivers, and more fires. A decrease in the commercial forest harvest and an increase in wheat production - but with greater irrigation needs - could be among the socioeconomic results.

But it is in the north the impact of global warming will be felt most sharply. According to Gignac, when the permafrost declines, the "soil turns to mush and banks slide into rivers." The eventual impact of massive soil erosion on northern communities on the Mackenzie River "could translate into an end to traditional aboriginal lifestyles."

When asked by a member of the audience if a difference in precipitation could alter his predictions, Gignac acknowledged it could. But he says, "It's a two-edged sword - there could be more precipitation than predicted and there could be less." Less precipitation would accelerate the effects of global warming.

Gignac hopes to build his model on a North American scale by heading east and north to Ontario, Quebec, the Maritimes and the subArctic. He stresses his model only tells us what ecosystems "want to do" if the globe warms up - how long it will take for them to redistribute is unknown. On the other hand, since peatlands are geared to the water table, "if it dries out a little, the whole vegetation complex changes," so the effects on plant life would be seen within only a few years.

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