Understanding the Effects of Arctic Tundra Fires

June 11, 2010 RSS Feed Print

By Marlene Cimons, National Science Foundation

Until recent years, fires on the Arctic tundra were rare. But warming temperatures and drier conditions have caused more lightning, which, in turn, has ignited an increasing number of wildfires. In 2007, the area experienced its largest yet, on Alaska’s North Slope, which scorched a swath of land roughly the size of Cape Cod.

“We were doing our work up there, and it was smoky, and we finally realized there was a big fire on the North Slope,’’ said Gaius (Gus) Shaver, an ecologist at the Marine Biological Laboratory in Woods Hole, Mass., who has been studying the tundra for more than 30 years and currently leads a National Science Foundation-funded study to better understand the fire’s environmental impact. “There have been other smaller fires, but this one was huge, and grew very rapidly.’’

Understanding the effects of these Arctic tundra fires provides a wealth of information about climate change, in particular the extent of carbon and energy exchanges between the land and the atmosphere. If the Arctic is frequently damaged by fire, very large amounts of carbon dioxide could be released into the air, especially if the land’s permafrost is disturbed, since the frozen soil there holds approximately one-third of the world’s soil carbon. “The burning put two million tons of carbon into the atmosphere,’’ Shaver said.

Initially, the team’s work was funded through awards from NSF’s Small Grants for Exploratory Research and later bolstered by money from the American Recovery and Reinvestment Act of 2009. The current NSF stimulus grant is $872,715 for three years. “This allowed us to fund more research than we could have done, and created jobs for many more people,’’ Shaver said.

The scientists have established a series of stations where they are monitoring the carbon balance, the exchange of carbon dioxide between the land and the atmosphere, and the energy balance. Automatic samplers are located in burned sites, as well as unburned sites, the latter to serve as a control, for comparison purposes. Sampling areas include streams.

“We want to look at changes in stream chemistry, and in lakes, changes in vegetation, in aquatic plankton and fish communities, and compare them with unburned sites,’’ Shaver said. “We are basically monitoring all the biological and geophysical changes in the area that were burned moderately, and burned severely. We have an unburned area almost totally surrounded by burned areas--that’s our control for the terrestrial stuff.

“This fire happened 26 miles north of Toolik Lake, a major research site where we’ve been working for 30 years, conducting long-term ecological research,’’ he continued. “We’ve been there since 1976 documenting how this system works, and comparing different types of systems, so we have this tremendous data base on how the system works just south of where this burn took place.’’

Among other things, the fire created a black surface much less reflective and more absorptive of solar energy, he said. “There is a lot of heat now going into the ground and into the permafrost,’’ Shaver said. “These are large disturbances that are happening with increasing frequency over a large area.’’

Most of the changes that are occurring in response to these fires are those that are reinforcing the initial stimulus, that is, “the warming is leading to more warming, which leads to an increase in fires, which leads to a greater amount of energy absorbed by the surface and transferred back into the atmosphere, which leads to more warming,’’ Shaver said. “We have a change that leads to a change that reinforces a change that reinforces the original change.’’

Shaver and his colleagues are looking at alterations that may occur in tundra vegetation, specifically whether conditions at burn sites will lead to new seeds or species. A warmer landscape may produce an increase in shrubs, for example, that could dominate much of the current grasses and mosses.

The climate changes in the tundra also could lead to harmful effects on the local economy. The North Slope is sparsely populated, although there are some small villages with several hundred people each. Also, about 5,000 individuals, most of them Native Alaskans, live in the nearby city of Barrow and depend on hunting and fishing for food.

“There are few sources of money,’’ Shaver said. “I am extremely interested in how a fire of this size will affect their supply of Caribou moose, and the fish in the lakes. It is very important for these people that we understand how the base of the food chain has been affected by the fire.’’