Imagine wheat, ripening under the warm Yukon sun in the fields around Whitehorse. It's not possible now, but it could happen in the future. Global warming could dramatically change the characteristics and potential of Yukon agriculture.

Difficult as it is to imagine after the short, cold summer of 1996, there is evidence that the world is gradually warming. Furthermore, the warming is at least partly the result of human activity, the effect of pollutants released into the atmosphere.

The earth's atmosphere acts as a natural greenhouse, trapping heat from the sun beneath layers of gases. Greenhouse gases, like water vapour, carbon dioxide, methane and nitrous oxide, occur naturally in the atmosphere. However, human activity contributes more of them, as well as adding a number of greenhouse gases that do not occur naturally.

The net effect appears to be a gradual warming trend, although how quickly the warming is taking place and how much is due to human activity are topics hotly debated by scientists.

Nevertheless, scientists in many fields are trying to predict the changes warming might bring to the environment and to human activity.

Scott Smith, head of the Yukon Land Resource Unit of Agriculture Canada's Research Branch, has looked at the potential changes in climate that could result from a doubling of the amount of carbon dioxide in the earth's atmosphere.

Climate models based on that level of carbon dioxide predict an increase of two to three degrees Celsius in the mean Yukon temperature, year-round.

"This kind of climate warming would really take us from being a marginal climate for agriculture to being a typical cool grain-growing type of climate," says Smith. The Yukon climate, according to the model, would be similar to that now experienced on the northern prairies.

Agriculture Canada measures the growing season in "growing degree days," which aren't actual days but rather a cumulative measure of how warm the days are through the growing season. Currently, the growing season in the southwest Yukon is only a little more than 800 growing degree days, long enough to grow hay or green feed but not long enough to ripen most grains.

It takes about 1000 growing degree days to mature a crop of wheat, and about 900 to mature a crop of barley. With an overall increase of two to three degrees, the season in the southwest Yukon would approach the 1000 days needed to ripen wheat.

In the Mayo and Dawson areas, where the summers are warmer, an across-the-board increase of two to three degrees would mean a growing season capable of consistently maturing spring-seeded grain.

Of course, temperature isn't everything, Smith says. "There are so many other variables that go into producing a crop."

Moisture is an important factor. The climate projections show an increase in rainfall, but that would likely be more than balanced by increased rates of evaporation. Smith says it's hard to say exactly how much moisture would be available for crops.

"Things would get drier, and irrigation would become increasingly important. I think that's the safest statement."

The quality of the soil is also an important factor. The prairies have grassland soil, rich in organic matter. Smith says the forest soils of the Yukon are extremely poor in organic matter and require heavy use of fertilizers in order to produce a crop.

However, with fertilizer, irrigation, and a marked increase in temperature, the Yukon's agricultural production could increase dramatically.

But will it happen? The answer is still very much an unknown.

"This stuff is fun to fantasize about, but we've got to remember that's all we're doing -- fantasizing," warns Smith. We still don't know enough about global warming to predict, only to speculate.

For more information about climate change and its impact on the Yukon, see the Yukon State of the Environment Report, available from Environment Canada, Whitehorse. (Visit the World Wide Web version of the Yukon State of the Environment Report.)