Creeping Desert

Will climate change push fertile prairie to desolate wasteland?

By Alex Roslin
Canadian Wildlife, September/October 2009

Water is the lifeblood of the Canadian Prairies—essential for its ecosystems, drinking and economy. But water experts say life could be turned upside down there as climate change brings severe drought, dried-up rivers and near-desertification to the Prairies in coming decades. Some of the impacts are already well underway.

“There is going to be tremendous stress on ecosystems,” says James Byrne, chair of the geography department at the University of Lethbridge. “It’s going to require substantial adjustment.”

“There will be a fair amount of problems in terms of agricultural production,” says Suren Kulshreshtha, an agricultural economist at the University of Saskatchewan. Impacts could include a 10 to 30 per cent drop in crop yields across the Prairies, according to Environment Canada.

Temperatures across the Prairies have already gone up by between one and four degrees Celsius in the past century, depending on the region. By 2100, they’re expected to go up a further 6.5 degrees under a median climate-change forecast in a landmark study coauthored by University of Alberta biologist David Schindler in 2006. He found that temperatures in northern Fort McMurray will be warmer than they are now in Lethbridge, 1,000 kilometres to the south.

Warmer temperatures, in turn, are behind a few parallel trends that are combining to imperil the Prairie water supply: melting glaciers and diminishing snowpacks in the Rocky Mountains, and increased evaporation of soil moisture.

Some of the hardest hit glaciers are in Montana’s Glacier National Park, which also sprawls into British Columbia and Alberta. Ice fields there help feed the South Saskatchewan River, whose waters meander across the Prairies and ultimately drain into Lake Winnipeg. This watershed is the main source of freshwater in a vast expanse of the southern Prairies.

But high up in the Rockies, rising temperatures over the past century have slowly melted 67 per cent of Glacier National Park’s icesheet. Scientists from the U.S. Geological Survey now estimate the last glaciers there will disappear by 2020—a decade earlier than initial estimates because warming is happening faster than expected.

“All of a sudden the park needs to be renamed because there are no glaciers,” says Stefan Kienzle, a University of Lethbridge hydrologist who studies climate-change impacts in the Prairies and in the mountain headwaters of the region’s rivers. Kienzle worked with other leading Canadian scientists to coauthor a landmark review of those impacts for Natural Resources Canada in 2007. They concluded that rising temperatures will bring widespread drought to the Prairies, especially in late summer, and that there will also be more frequent severe droughts.

Many rivers and streams will dry up, and wildlife that depends on them will be devastated. “A large number of Prairie aquatic species are at risk of extirpation,” the review said.

Byrne, who was one of the lead authors of the study, says the Prairies will eventually turn into an arid tropical zone like Arizona, especially in summertime, with near-desert conditions in some areas. “Overall, the biggest concern is we’re going to see a big increase in variability (of the Prairie climate),” he says.

River flows in the three Prairie provinces are already down substantially. A severe drought in 2001 and 2002 caused an estimated $5.8-billion drop in Canada’s gross domestic product and 41,000 lost jobs, mostly in the Prairies. A study commissioned for Agriculture and Agri-Food Canada tied it to climate change and called for better preparedness to counter “the increasing threat of drought risk."

One of the key unanswered questions is the fate of the massive Columbia Icefield straddling the Alberta and B.C. border. This 365-metre-thick chain of glaciers is the largest mass of ice and snow in the Rockies and helps feed a watershed that spans the central and northern Prairies.

But this icefield is also retreating. One of its main components, the Saskatchewan Glacier, which is the primary water source for the North Saskatchewan River, has retreated 1.4 kilometres in the last 100 years. Another component, the Athabaska Glacier, has lost half its volume.

Low river flow in the late summer will have significant implications for wildlife in the watershed, says Kienzle. “It will put more stress on the ecosystem and on all species that depend on the rivers.”

LOW FLOW

Climate change is already affecting rivers in the Canadian Prairies. Summer river flows are 20 to 84 per cent lower than 100 years ago, according to a 2006 study coauthored by University of Alberta biologist David Schindler, which appeared in the Proceedings of the National Academy of Sciences.

“We were shocked by how extreme the changes in river flows had been,” a profile of Schindler in the journal quoted him saying. He added that the decline of Canada’s freshwater “might be the largest crisis facing that nation in the upcoming century,” the article said.