July 07, 2006
Study suggests peat bogs may affect global climate
CARBONDALE, Ill. — Peat bogs might conjure images of misty, swampy wastelands. But a Southern Illinois University Carbondale professor wants you to think of them as giant stores of carbon that can have a major impact — good or bad — on the global temperature.
Dale Vitt, professor and chairman of the plant biology department in the College of Science at SIUC, recently visited Siberia, site of the world's largest peat deposit. Vitt, who has studied the bogs for some 30 years, recently received a $34,000 grant from the National Science Foundation to organize an international survey of peat bog knowledge and management practices.
The Siberian bog, along with one in western Canada that is the second largest on Earth, hold vast amounts of carbon in the form of plant biomass. In a sense, the bogs act like great sponges, soaking up carbon and holding it in place.
And we're talking about a lot of carbon.
"A full one-third of all the terrestrial carbon on the planet is in peat," Vitt said.
To understand the bogs' impact on the environment, one has to understand plant systems.
In normal, balanced systems such as the forests around Southern Illinois, the plants use photosynthesis to take the carbon dioxide out of the atmosphere. Microscopic creatures then release the carbon as a gas when they eat the material that falls to the floor, decomposing it.
Peat bogs, however, develop when thick vegetation grows in a waterlogged area. The plants still take the carbon dioxide out the atmosphere. But as the water in the area becomes anaerobic — that is, without oxygen — it greatly slows the rate of decomposition of the plant material, allowing it to build up rather than flow back into the environment as a gas.
"You can think of it in terms of carbon input and output," Vitt said. "Usually, things decompose about as rapidly as they grow. Peat lands are essentially unbalanced systems. More carbon comes in than decomposes. The bugs that live in that kind or anaerobic environment are poor decomposers."
Because of the bogs' ability to hold carbon, Vitt said they play an important role in how much carbon dioxide is in the atmosphere. Carbon dioxide is considered a "greenhouse gas" that contributes to warming the environment.
A major thrust of Vitt's research is finding out how these expansive bogs formed and why.
"Peat bogs in North America are about 3 meters deep, but in Siberia they're 5 meters deep. Why?" Vitt asked.
Some theories hold that a dry period in North America 7,000 to 10,000 years ago led to the vast prairies forming. The dry climate prevented bogs from forming as readily in North America as they did in Siberia, where bogs began forming about 3,000 years earlier than those in North America.
Another reason may be that North America was more prone to thick stands of trees, which are susceptible to intense fires that are another detriment to bog formation.
Vitt's work has some implications for the ongoing debate about global warming. Although warming and cooling cycles have happened naturally throughout the ages, Vitt said the combination of an apparent warming cycle coupled with additional carbon emissions caused by humans might have an impact on the bogs as well.
"The models say Canada, for instance, is going to have a warmer, dryer climate. They may be wrong, but that's what they say."
Such a change might cause decomposition in peat bogs there to accelerate, adding a huge amount of carbon dioxide to the atmosphere and potentially increasing the "greenhouse effect." Vitt said large oil deposits in the areas of the great bogs also might encourage more exploration, potentially disturbing the bogs' operations.
"This is a big amount of carbon and we should think carefully about what we do with bogs," Vitt said.
Vitt is working with an international team of scientists to pool their knowledge of the great peat bogs. The team is writing a paper and will present it next summer at an international conference. It also will study tree ages and distribution on bogs and will seek a large, international grant to perform a definitive study of the Siberian peat lands.