Are Alaska's wildfires accelerating global warming?


A quick primer for the climate impaired

The natural presence of certain gases like carbon dioxide in the air helps keep the Earth warm enough for life to exist. Solar radiation warms the planet, and these gases slow the loss of that heat back into space. They act somewhat like glass in a greenhouse, hence the nickname. In the past, when the level of CO2 rose -- maybe due to vast rotting swamps or volcanic action -- the climate grew warmer. Sometimes much, much warmer.

And when CO2 levels plunged? Can you say ‘Ice age'? After thousands of years of relative stability, Earth's CO2 concentration has lately been rising fast, in synch with the burning of fossil fuel by industrialization and the emissions of modern life. The Earth's CO2 level is now almost 390 parts per million, according to the latest measurements posted by the Mauna Loa Observatory in Hawaii.

So, when was the last time CO2 concentrations were that high? About 15 million years ago, according to this 2009 study led by UCLA scientist Aradhna Tripati. A very different Earth, that. Global temperatures were 5 to 10 degrees warmer, and there was no permanent ice in the Arctic. Sea level was at least 75 feet higher. This could be our future.

A series of warmer summers and drier springs in Interior Alaska has forced wildfires to burn deeper into the region's ancient peat, releasing far more carbon dioxide into the air than previously thought, according to a new study by a team of scientists.

The longer-burning fires, and longer burn season, has dramatically increased the release into the atmosphere of carbons stored over eons by Alaska's black spruce ecosystem, a dynamic that threatens to accelerate global warming even more.

The result may be a climate game-changer.

Alaska's boreal forests -- long thought to be one of the Arctic's main carbon sinks and a stabilizing influence against global warming -- have begun to spew out more greenhouse gas than they take in, according to a study by University of Guelph plant biologist Merritt Turetsky, of Ontario, Canada, and six other researchers.

"Essentially this could represent a runaway climate change scenario in which warming is leading to larger and more intense fires, releasing more greenhouse gases and resulting in more warming," said lead author Turetsky, in a release about the study, to be published in Nature Geoscience. "This cycle can be broken for a number of reasons, but likely not without dramatic changes to the boreal forest as we currently know it."

Study co-author Eric Kasichke, a professor of biogeography at the University of Maryland, said the research amounts to the first demonstrated link between burned area and increases in fire severity. "This not only impacts carbon storage, but also will accelerate permafrost loss and changes in forest cover," he added.

The findings dramatize the critical role the Arctic plays in global climate change, driven by the increasing concentration of atmospheric greenhouse gases produced by human activity and the burning of fossil fuel.


Measured over decades, the North has seen shifts in sea ice, snow cover, vegetation, wildlife, permafrost and air temperature.

"This includes longer snow-free seasons, changes in vegetation, loss of ice and permafrost, and now fire, which is shifting these systems from a global carbon sink toward a carbon source," said study co-author Jennifer Harden, a U.S. Geological Survey scientist.

The National Oceanic and Atmospheric Administration determined in its 2010 Arctic Report Card that climate change in the North isn't a short-term aberration.

"It is clear that the Arctic is experiencing the impacts of a prolonged and amplified warming trend," NOAA stated in the report. "It is very likely that Arctic climate warming will continue and we will continue to see records set in years to come."

Not every season is hotter than the last, of course. Nor does every region show warming every year. Global warming can deliver regional cooling, big storms and strange weather -- such as Alaska's unprecedented November rain.

Alaska's average annual temperature rose about 3 degrees Fahrenheit between 1949 and 2009, according to the Alaska Climate Research Center, which attributes the rise to a major step-up in air temperatures in the mid-1970s, coupled with record warmth of the mid-2000s. Yet throw in the recent, somewhat cooler years, and the same stations show that Alaska actually chilled by a tenth of a degree since 1976.

(A 30-year warming trend in the Bering Sea just got interrupted by the three coldest years on record, according to a recent study by Alaska scientist Alexei Pinchuk.)

Still, measured across many decades, climate change in Alaska now threatens to free carbon stored one leaf and stick at a time during thousands of years inside the thick beds of peat and permafrost of Alaska's black spruce forests.

About half of all the soil carbon in the world is locked into the peat and permafrost of the North, and that includes Alaska, Turetsky said. Left to a "normal" carbon processing pattern, these boreal forests tend to have a net cooling effect on the globe. But blast them with fire, and all that carbon can soar into the sky where it contributes to the greenhouse effect.

"When most people think of wildfires, they think about trees burning, but most of what fuels a boreal fire is plant litter, moss and organic matter in surface soils," Turetsky explained. "This is carbon that has accumulated in ecosystems a little bit at a time for thousands of years, but is being released very rapidly through increased burning."

A perfect firestorm

Wildland fire has been a natural and necessary part of Alaska's boreal forest ecology for at least 6,000 years, scientists say. When a gnarly and ragged stand of black spruce burns off, the landscape rejuvenates in an explosion of new growth -- first sprout fireweed and herbs and blueberries, succeeded by shrubs that feed a furious rebound in moose. Finally, after 30 to 40 years, black spruce dominate again, and the cycle repeats.

Alaska's migratory Native groups understood this process well and took advantage of it in their quest for food. Scientists say Gwich'in Athabascans even sparked their own wildfires in eastern Alaska in an effort to "manage" resources and improve hunting. (For a fascinating discussion, check out this study.)

But Alaska's fire ecology has been changing fast in recent years. Extensive stands of highly flammable black spruce now dominate nearly half of Interior Alaska -- and these stands are older and more vulnerable to fire than at any time in the past century, according to University of Alaska Fairbanks scientist F. Stuart Chapin.

The reasons are complex, reaching back into the 19th century, when disease outbreaks decimated Interior Native populations and perhaps decreased the amount of burning Natives themselves conducted in the eastern Interior, wrote Chapin and 14 co-authors in Bioscience in 2008.

Then came a "pulse of fire" triggered during the Gold Rush in the early 20th Century, setting the stage for re-growth by black spruce up and down the Yukon River drainage.

Over the past half century -- as formerly migratory Natives settled into permanent villages and towns spread along the road system -- people began to aggressively suppress fires in this aging taiga near communities, allowing fuels to build up and the stands to become even more prone to burning.

"Thus, a combination of factors has increased landscape flammability, particularly in areas close to communities, just when climate warming has increased the likelihood of large, uncontrollable wildfires," Chapin wrote.


Pepper up the Interior's fire seasons with hotter, drier weather, and what do you get? During the 2000s, wildfires scorched about 1.8 million acres per year in Alaska -- a 50 percent increase over any previous decade since the 1940s, according to a previous study led by Kasichke.

The record season struck in 2004, when 696 fires raged across 6.5 million acres -- an area larger than Vermont. The amount of carbon dioxide sent skyward over the 90-day season was estimated at 56.7 million tons -- more than was released by U.S. domestic airlines over the entire year. Last year, 689 fires burned through about 1.1 million acres, also above average.

Turetsky and the other researchers took to the field during this fire surge. Between 1983 and 2005, they measured how deep fires burned at 178 sites spread among 31 fires in Alaska's black spruce forests to find how much carbon was burned. They also analyzed 296 samples from 43 mature, unburned black spruce stands, and conducted a series of complex calculations.

"This study suggest that fire-regime changes over the past decade ... have caused Alaska boreal ecosystem to switch from a long-term net soil (carbon) sink toward a (carbon) source," the authors concluded.

Unintended consequences

The trend of more searing and extensive wildfires will impact Alaska beyond accelerating the release of greenhouse gases, Kasichke wrote in an e-mail last week.

"For example, the deeper burning fires will accelerate the warming of permafrost, and in some cases, result in the loss of permafrost," Kasischke said. "In addition, in many areas, the deep burning fires will cause a shift in forest type, from spruce dominated forests to aspen and birch dominated forests. This in turn, will impact the role the sites play in terms of wildlife habitat."

What can be done? For instance, should Alaskans shift tens of millions of dollars into suppressing fires in wilderness areas that are now allowed to burn?

"Practically, this would be very difficult, given that fires can be very large and burn in remote locations," Turetsky said. "Fire management can lead to unintended consequences. For example, fire suppression has been related to the dramatic mountain pine beetle outbreak in British Columbia.


"Having said that, I know that fire management agencies in Canada are being proactive and thinking more about protection of resources other than timber, such as carbon rich peat lands. We don't know much about what ignites a smoldering peat fire, or how long they burn."

Alaskans are aware of the changes at hand, too, Harden added.

"All of the resident Alaskans I've talked to are keenly aware of changes in the seasonal climate and animal browse, and (how) the recent fires in the Interior affected everyone traveling or with asthma. Interior fires are too huge to fight, so these smoky summers and falls are just something to cope with," he said via e-mail.

Wildfire: 'A beautiful terror'

Charging into fire zones and tramping through soot past still-glowing embers was a startling experience for the scientists. It offered wondrous sights and a few close calls.

After a field trip toward an old fire scar near Tolovana Hot Springs in 2003, Turetsky and colleagues were driving toward the highway when a new fire erupted near Ericson Creek -- a fire that ultimately burned for months.

"We saw the ignition," Turetsky said. "We drove towards the flaming that afternoon in our field truck and realized that the fire was larger than it looked from a distance. I was behind the wheel, and had trouble staying on the road due to poor visibility. When we came out of the smoke, I realized that several sedans were following us out, using our truck as a guide."

Turetsky also relished going "backcountry" with fire crews in 2003 with co-author Kristen Manies. At first, they really stuck out because of their squeaky clean faces.

"A few days later, no one could tell that we were scientists and not fire fighters," she said. "We had char everywhere, including in our ears."

Harden remembers donning full safety gear and riding an ATV into freshly burned landscape the morning after one Interior fire in the Caribou-Poker creeks area about 30 miles north of Fairbanks.

"You read about 'beautiful terror' -- well fire is like that," she wrote in an e-mail last week. "Ash pillows -- they disperse on the gentlest breath; survivor moss -- green sheep in a field of black; glowing embers reminiscent of the frightful heat..."

"Now that watershed thrives in shrubs and little trees," she added. "Fire isn't evil and it's not forever."