In Far North, Peril and Promise
Thursday, February 22, 2007
PINE FALLS, Manitoba -- Here on the edge of the silent and frozen northern tier of the Earth, the fate of the world's climate is buried beneath the snow and locked in the still limbs of aspen trees.
Nearly half of the carbon that exists on land is contained in the sweeping boreal forests, which gird the Earth in the northern reaches of Canada, Alaska, Scandinavia and Russia. Scientists now fear that the steady rise in the temperature of the atmosphere and the increasing human activity in those lands are releasing that carbon, a process that could trigger a vicious cycle of even more warming.
The prospect of the land itself accelerating climate change staggers scientists, as well as woodsmen such as Bob Austman, who stopped recently in a quiet stand of birch on the edge of the boreal forest to examine a jack rabbit's tracks.
"There are big forces out there," he said succinctly.
Those forces, which scientists are only starting to understand, could free vast stores of carbon and methane that have been collecting since the last ice age in the frozen tundra and northern forests. Their release would push the world's climate toward a heat spiral that would raise ocean levels, spawn fierce storms and scorch farmlands, scientists believe.
But the land is impartial. It could also be enlisted to help abate global warming, as both a storehouse for man-made carbon dioxide and a natural sponge for greenhouse gases. Policymakers are considering changes to protect and expand the forested areas that store carbon; outside the boreal forest, they are experimenting with techniques to bury man-made carbon dioxide in underground vaults and porous seams.
"The world is both victim of climate change and a possible solution to it," said Stewart Elgie, associate director of the Institute of the Environment at the University of Ottawa.
Carbon is freed from the land in numerous ways. Permafrost melting because of warmer weather exposes peat, deadwood and buried pine needles to decay, freeing the carbon they contain. Fires, raging through forests more often because of hotter and drier weather, send wood -- and its carbon -- up in smoke. Insects thriving in milder winters girdle trees and send them to rot on the forest floor. Miners and oilmen build roads that expose the earth and warm the land, and loggers cut down old forests and replace them with young ones that will take decades of growth to absorb and store the same amount of carbon.
As the released carbon rises, it adds to the belt of greenhouse gases in the atmosphere, trapping even more heat, which causes more warming. Scientists call it a "feedback loop." Others have a more ominous term: the carbon time bomb.
Risk Poorly Understood
"We are taking risks with a system we don't understand that is absolutely loaded with carbon," said Steven Kallick, a Seattle-based expert on the boreal forests for the Pew Charitable Trusts. "The impact could be enormous."
Scientists acknowledge they are not certain how the carbon time bomb will explode, or when. Many of the consequences of global warming that experts once predicted would take centuries are occurring in decades, such as the melting of the world's glaciers and ice caps. But other changes might be more gradual.
"With permafrost, it may take longer for change to get moving. But it may keep moving, even if we get our emissions under control," said Antoni Lewkowicz, a professor of geography at the University of Ottawa. "It's like a big boulder. Once you get it moving, it won't stop."