But nothing in nature is so simple. As tundra warms, the tree line may migrate north, and the fresh growth of forest may soak up more carbon from the atmosphere than the soil releases. In areas of discontinuous permafrost, where forests topple as the ground collapses, emerging wetlands may also sequester more carbon than the forest that preceded them. On the other hand, climatic warming is already increasing the acreage of Northern forest that burns every year, a trend likely to accelerate — and burning forest releases huge amounts of CO2. We just can't be sure how these forces will play out.
One thing we can be sure of is the critical role of the peat and moss that cover permafrost. Destroy that layer of insulation, and the ground will be as exposed to the sun as is bare skin. Yet, in our zeal to build, we often ignore the guardian role of moss and peat. All around Fairbanks, land has been cleared of forest and moss to build homes, hundreds of which are now settling at odd angles as permafrost thaws. In Kotzebue, a hospital damaged by melting permafrost was abandoned. So was a radio transmitter site near Fairbanks, and miles of roadway across interior Alaska.
It is earliest autumn, and as I drive with Tom Osterkamp on the road to Mount McKinley, he exclaims with delight whenever he sees a yellow birch. The road heaves and dips and falls away at the shoulder into newly formed pits and pools of meltwater. "Thermokarst," he points out, again and again. I have grown to recognize it, as I suspect will many others, as climate and land change.
By Bernice Wuethrich