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Study: Siberian Bogs Big Player in Greenhouse Gas

James Owen
for National Geographic News
January 15, 2004
 
Northern Russia's vast peat bogs may play a pivotal role in regulating
greenhouse gas levels throughout the world, according to a new study.

The barren peatlands of Siberia have been a massive methane producer since soon after the last ice age some 12,000 years ago, far longer than previously thought, scientists say. They also found evidence that suggests peat bogs rank among the world's top carbon stores, absorbing huge amounts of carbon dioxide from the atmosphere.


Both methane and carbon dioxide are key greenhouse gases. They absorb long-wave radiation and trap heat in the Earth's lower atmosphere. The research team says this makes northern Russian a major player in future global warming scenarios.

"The study shows the potential role of Siberian peatlands as a major piece of the greenhouse gas puzzle, both in the past and the future," said Glen MacDonald, chair of geography department at the University of California, Los Angeles (UCLA), and co-author of the study published today in the research journal Science.

UCLA researcher Laurence Smith led a 22-member international team to the West Siberian Lowland. The region—a flat, mosquito-infested plain of wetlands, tundra, and scattered larch forests—covers half a million square miles (1.3 million square kilometers), the largest expanse of peatlands in the world.

"If you pushed all the individual peat bogs together they themselves would cover at least 233,000 square miles [603,445 square kilometers], almost as big as Texas," Smith said.

Radiocarbon Dating

Radiocarbon dating revealed that the bogs were 2,000 to 3,000 years older than previously thought, and researchers believe the bogs may be responsible for a huge rise in atmospheric methane levels (identified from Arctic ice core records) 9,000 to 11,500 years ago.

Previous explanations for this rise in methane gas included catastrophic releases from the seafloor and emissions from tropical rain forests. "Now we [also] suspect these peatlands," said Smith.

Peat forms in cool, wet regions, especially at northern latitudes, where dead plant material doesn't fully decompose. Over time, peat builds up in layers thousands of years old. Where the ground is particularly soggy and oxygen-poor, anaerobic bacteria attempts to digest organic matter, producing methane gas and a noxious odor.

Smith says the methane spurt during the early Holocene period is probably best attributed to a combination of factors, including warming temperatures and closer plant contact during the early stages of peat formation with the nutrient-rich, mineral substrate.

Core samples of the peat, which reaches depths of 33 feet (10 meters), revealed that different species typical of low wetland areas dominated at the time. The study team calculates these plants would have produced about six times more methane than today's bog-dwelling plants such as sphagnum moss.

Yet these same peatlands are credited with converting another greenhouse gas, carbon dioxide, into harmless carbon held in the soil. Because peatland vegetation doesn't properly decompose, much of the carbon dioxide taken in by living plants isn't returned to the air.

Carbon Store

The new study suggests the West Siberian Lowland alone accounts for between 7 to 26 percent of global carbon reserves accumulated since the last Ice Age. Globally, peatlands contain an estimated 550 billion tons (541 billion metric tons) of stored carbon. If this carbon sink were released back into the atmosphere as carbon dioxide gas, the consequences could be dire.

Signs in northern Russia indicate this process may be about to start.

Smith said: "Sea ice is melting so quickly that it's at the lowest extent ever seen before. Shrubs are sprouting up in what used to be tundra. The growing season has lengthened, and the tree line may even be moving north. Studies have shown that permafrost is degrading at its southern boundaries, and permafrost temperatures are rising further north. There's no question that the Arctic is really heating up."

Similar concerns exist in other countries. At an international climate change conference in Milan, Italy, last month, the conservation group Wildlife Habitat Canada warned that climate change modeling studies forecast very severe effects on peatlands in the mid-belt of Canada. Peatlands cover 12 percent of the country.

The UCLA-led team says warmer temperatures, coupled with melting permafrost and a lowered water table, could eventually lead to aerobic decomposition due to peatland drying and increased soil oxygen levels. As a result, carbon dioxide would be produced instead of methane. They calculated that the long-term benefits of lower levels of methane (which has a shorter lifetime in the atmosphere) could be significantly outweighed by the increase in carbon dioxide, leading to "a positive warming impact to the atmosphere."

Smith added: "Since we focus so much today on manmade sources of greenhouse gases, it's easy to forget that global climate changes also occur naturally. But we're in uncharted territory when it comes to combining manmade sources with natural sources."

Smith cautions that if the Siberian peatlands, with 11,500 years' worth of carbon dioxide stored in them, start to rot away, we could be in for a shock.
 

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