Indonesia Rainforest Fires Doubled CO2 Levels Globally

by Cat Lazaroff

A team of scientists led by Susan Page from the University of Leicester in the United Kingdom attempted to estimate the mount of carbon released by the 1997 fires, and their potential effects on global warming. In an article published in the November 7 issue of the journal "Nature," the researchers conclude that these fires were "a major contributor to the sharp increase in atmospheric CO2 concentrations detected in 1998."

Fire on Mt. Suharto, Borneo, March 1998

From 1997 to 1998, the growth rate of CO2 in the atmosphere nearly doubled, from an average of 3.2 gigatons per calendar year to 6.0 gigatonnes, the highest value on record.

Most of the carbon released in the Indonesian fires came not from burning trees but from smoldering peat bogs which lost between 25 and 85 centimeters (about 10 to 33 inches) of their depth in the fires.

Tropical peatlands form one of the largest land reserves of organic carbon. Peat is a carbon rich soil made of compacted, decayed vegetation. Peat bogs like those found in Indonesia normally support lush swamp forests over peat deposits that can be up to 20 meters (66 feet) thick.

But when forest clearing, drainage and drought begin to dry out these peatlands, they become susceptible to fire -- as was demonstrated during the 1997 El Nino driven dry season.

Using satellite images of a 2.5 million hectare study area in Central Kalimantan, Borneo, from before and after the 1997 fires, the researchers calculates that about 32 percent, or almost 800,000 hectares, of the area had burned. Peatlands accounted for 91.5 percent of the burned area, or about 730,000 hectares.

"Using ground measurements of the burn depth of peat, we estimate that 0.19-0.23 gigatonnes (Gt) of carbon were released to the atmosphere through peat combustion, with a further 0.05 Gt released from burning of the overlying vegetation," the team wrote in the "Nature" article.

"Extrapolating these estimates to Indonesia as a whole, we estimate that between 0.81 and 2.57 Gt of carbon were released to the atmosphere in 1997 as a result of burning peat and vegetation in Indonesia," an amount equal to between 13 and 40 percent of the average annual carbon emissions caused by the burning of fossil fuels around the world.

The CO2 released by the fires was more than all the carbon taken up by all living things on the planet -- collectively known as the biosphere -- in a single year.

The 1997 fires were therefore likely responsible for the massive boost in CO2 emissions seen in 1997-1998 -- the largest annual increase in atmospheric CO2 concentration detected since records began in 1957, according to the researchers.

Indonesia's 1997 and 1998 fire seasons were massive, destroying about 10 million hectares (38,600 square miles) of Indonesia's national forests, recognized as one of the world's centers of biodiversity.

More than 20 million people were exposed to breathing extremely high levels of pollutants known to cause both acute and long term health effects. Schools and businesses were closed in Malaysia and people were advised to remain indoors.

But the problem did not end with the easing of the dry El Nino weather pattern. Wildfires, mostly sparked by humans clearing forest for agriculture, and exacerbated by increased logging in the years following the fires, caused major problems again in 2000, and problems may be cropping up again this year.

These fires destroy some of the habitat on which a variety of endangered species, such as bears, elephants, rhinos, tigers and orangutans, depend. Birute Galdikas, a primatologist who began her orangutan research in 1971, said the number of orangutans in Indonesian Borneo has been halved in the past decade, partly due to the fires as well as logging and mining.

But besides the catastrophic effects that tropical wildfires may have on biodiversity, researchers must consider the impact that relatively small areas of fire may have on the planet as a whole, through their contributions to global climate change.

Natural, undamaged peat swamp forest is "essential to maintain high water levels, protect the peat carbon store and facilitate future carbon sequestration from the atmosphere," the researchers conclude.

That position is echoed by an essay that accompanies the "Nature" article, written by two scientists from the U.S. National Center for Atmospheric Research.

The researchers, David Schimel and David Baker, note that Susan Page and her colleagues have shown that "abrupt events can have an appreciable effect on the carbon cycle."

"Most observing systems and modeling strategies assume that, to affect the carbon cycle, processes must occur over thousands of square kilometers or more," they write. "But especially in areas of high carbon density, catastrophic events affecting small areas can evidently have a huge impact on the global carbon balance."

The Indonesian wildfires show that attempts to slow the rate of global warming will have to focus not only on reducing direct human caused carbon emissions from factories, power plants and vehicle tailpipes, but also on efforts to stem the unsustainable destruction of massive carbon stores such as those found in tropical forests and peat bogs.

If tropical peat forests continue to be destroyed by logging, development and fire, "there will be a continued release of carbon through decomposition of the exposed peat surfaces that, in turn, will place this large carbon store at further risk," write Page and her colleagues. "Tropical peatlands will make a significant contribution to global carbon emissions for some time to come unless major mitigation, restoration and rehabilitation programs are undertaken."