If you take the long view, if you look at the geological scale, climate change is nothing new.

Fifteen thousand years ago, much of the southern Yukon was buried under a kilometre of ice and the northern Yukon was a haven of grasslands and game. Even longer ago, lush forests grew on what are now barren Arctic islands.

So why the big fuss about the current pattern of climate change?

Several things are different this time around, says Don Lemmen, an Ottawa-based climate change scientist with Natural Resources Canada.

"This is the first time in the planet's history that human activity is a significant, indeed dominant, factor in controlling climate change."

Logically, if humans can help create climate change, we should be able to do something about mitigating it, he adds.

"Second is the rate of change," says Lemmen. "The climate is changing much more rapidly than it has for at least 10,000 years."

That speed is significant. Natural systems can adapt to change, and have adapted repeatedly in the past. But the adaptation happens slowly, over years and generations.

If change happens more quickly than systems can handle, the results can be disastrous. Mass extinctions in the distant past, including the disappearance of the dinosaurs, may well be related to environmental change that happened more rapidly than the organisms could handle.

Human social and economic systems are also vulnerable to change, Lemmen points out, and they too need time to adapt. In fact, modern humans need quite a bit of time.

The last time a major climate shift hit the Yukon, the local human population was small and nomadic. When conditions became difficult, people could move their homes and families to a new location with relative ease. The modern Yukon population is both much larger and much less mobile.

The third factor that makes this round of climate change different, says Lemmen, is stress.

"Most systems today, both human and natural, are under considerable stress from a number of factors besides climate change," he says.

"Decreased biodiversity, habitat fragmentation, persistent organic pollutants, and other factors have placed many natural ecosystems under such stress that they are less able to cope with changing climate than they were in the past."

On the human side, there are stresses related to social and economic change, uncertainty, and the struggle to create sustainable communities based on finite resources. Climate change adds another level of stress, and a significant one in the North.

"Climate-related changes have already been observed in the Yukon," adds Fiona Warren, a science advisor at Natural Resources Canada. "For example, disturbances such as forest fires and insect infestations appear to be increasing."

Other costs and stresses are beginning to show up. Communities and industries that rely on ice roads or ice bridges have experienced unusually short ice-road seasons over the past few winters. Melting permafrost and increased storm action are contributing to rapid erosion on the Beaufort Sea coast. Caribou have had trouble reaching their calving grounds before spring break-up.

We can't stop the warming, Lemmen says. Even if we stop pumping out the greenhouse gases that are contributing to climate change, the warming process will only slow down, not stop. But a slow-down would help.

Reducing the rate of change will give us more time to adapt and to plan for a different kind of climate, he explains.

"An immediate task is to decrease our vulnerability to climate change. Preparing for adaptation now will help the Yukon minimize the negative impacts of future climate changes and take advantage of potential opportunities."

For more information about climate change, contact the Northern Climate ExChange at Yukon College in Whitehorse, (867) 668-8874, or go to www.taiga.net/nce.