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Wildfires gain ground on Alaska tundra

Posted: Wednesday, July 16, 2008

DIMPLE LAKE - The Arctic is burning.

It long has, of course, but now with greater regularity and more ferocity. Splinters of lightning crackle on the tundra, setting ablaze runaway fires that toast the landscape black.

Around this remote pond deep in the Arctic Circle, the ground is a singed sponge dotted with charred clumps of tussock grass. Nearby an emerald carpet covers nearly every inch of tundra in one shade or another of green, as it typically does for the 300 or more years that usually pass between fires.

Adrian Rocha, a physiological ecologist, excitedly strolls the undulating burnscape.

The fire that incinerated the land from July into September last year is the largest ever recorded on Alaskan tundra. It cleared a swath of 400 square miles far from civilization. It followed a pair of forest fires earlier in the decade that had ranked one and three on the list of largest on record in the state.

Rocha patches the hose of a sample-gathering water pump chewed apart by a grizzly bear and slips a new data card into a $50,000 patchwork of scientific equipment that listens silently to the ecological changes wrought on the recovering ground.

The gadgets could tease new secrets from the environment. Foremost among them, will more fires beget a warmer world?

One finding: It turns out looks do matter.

"You can see that the surface is really dark," said Rocha, a researcher at the Marine Biological Laboratory. In fact, the ground is mostly coal-mine black rather than the vibrant green that blanketed the land before fire came.

"More of the sun's energy is heating up the soil," he said.

Just 3 percent of the light that strikes this ash-black ground is reflected back, compared with 18 percent on leafier, unburned ground.

Soil temperatures run 3.6 to 5.4 degrees hotter. And the ground thaw runs about 10 inches deeper than beneath unburned tundra - perhaps because it absorbs more sunlight, maybe because a layer of insulation against winter cold was stripped away, or both.

The fire itself kicked massive amounts of carbon dioxide into the air. All wildfires do that. But even though the Arctic covers less than a sixth of the planet's land mass, it holds about one-third of the planet's stored carbon, in part because of the slow rate of decomposition in the previously frozen north.

With more of that soil taken out of the permafrost, the dirt is awakened to the activity of microbes that could release greater levels of carbon dioxide into the atmosphere.

If the research going on here now finds that happening, the increase in Arctic fires could set in motion what scientists call positive feedback: greenhouse gases making for a hotter, drier Arctic that burns more often and kicks up even more greenhouse gases.

"These fires have everyone thinking this is part of a pattern," said Wendy Loya, an ecologist for the Wilderness Society in Anchorage. "You've got dramatic increases in temperature and a little more precipitation. But the extra rain isn't enough to offset the warmer temperatures and the longer growing seasons. ... You get more fires."

This year, it turns out, has seen fewer Alaskan wildfires. Although a portion of the Arctic burned last week along the Yukon River, interior Alaska so far has seen just 297 wildfires torch about 43,000 acres of wilderness.

In 2005, the state lost 5 million acres of forest and tundra to fire. In 2004, about 6.5 million acres burned.

The area struck by wildfire in the state tripled from the 1960s to the 1990s.

In fact, a recent article in the journal Bioscience said fire in Alaska is more severe this decade than it has been in 150 years.

And unlike the lower 48 states, Alaska firefighting is approached far differently. In the 1980s, Alaska was split into three kinds of fire zones. In about 17 percent of the state fire is fought aggressively to protect life and property. An intermediate zone sees fire fought only early in the season to provide a buffer for populated areas, but is left to burn late in the season when rain can be expected to quell it.

Yet on two-thirds of the Alaskan interior, fires are almost always allowed to burn. That's partly because the areas are too large and too remote for firefighting to be effective, and partly because it allows for a natural regeneration of the landscape.

The policy has been mostly lauded in environmental circles.



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