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Untouched Forests Store More Carbon

Posted on: Monday, 4 August 2008, 14:20 CDT

A new Australian study of "green carbon" and its role in climate change suggests that untouched natural forests store three times more carbon dioxide than previously estimated and 60 percent more than plantation forests.

Green carbon occurs in natural forests, brown carbon is found in industrialized forests or plantations, grey carbon in fossil fuels and blue carbon in oceans.

The role of untouched forests, and their biomass of green carbon, had been underestimated in the fight against global warming, according to Australian National University (ANU) scientists.

The U.N.'s Intergovernmental Panel on Climate Change (IPCC) and the Kyoto Protocol did not distinguish between the carbon capacity of plantation forests and untouched forests, scientists said.

However, the ANU report released on Tuesday said untouched forests can carry three times the carbon presently estimated, if their biomass of carbon stock was included.

Currently, forest carbon storage capacity is based on plantation forest estimates.

The report "Green Carbon, the role of natural forests in carbon storage" said a difference in the definition of a forest was also underestimating the carbon stock in old-growth forests.

Trees taller than 2 meters (six feet) and a canopy cover greater than 10 percent were the IPCC’s definition of a forest, but in Australia a forest was defined as having trees taller than 10 meters (33 feet) and a canopy cover greater than 30 percent.

Southeast Australia's unlogged forests could store about 640 tons per hectare (1,600 tons per acre), yet the IPCC estimate put it at only around 217 tons of carbon per hectare, the report said.

Around 9.3 billion tons of carbon can be stored in the 14.5 million hectares of eucalypt forests in southeast Australia if they are left undisturbed, scientists estimated.

According to IPCC estimates, only one third of this capacity and only 27 percent of the forests' biomass carbon stock.

Not only did natural forests store more carbon but because they remained untouched, they stored the carbon for longer than plantation forests which were cut down on a rotation basis.

Natural forests are more resilient to climate change and disturbances than plantations, the report found.

“Protecting natural forests serves two purposes: it maintains a large carbon sink and stops the release of the forest's stored carbon,” said Co-author of the report Brendan Mackey.

He said protecting the carbon in natural forests is preventing an additional emission of carbon from what we get from burning fossil fuel.

The report says the carbon stored in the world's biomass and soil was approximately three times the amount in the atmosphere. About 35 percent of greenhouse gases in the atmosphere is a result of past deforestation and 18 percent of annual global emissions is from continued deforestation.

Logging resulted in more than a 40 percent reduction in long-term carbon compared with unlogged forests.

"The majority of biomass carbon in natural forests resides in the woody biomass of large old trees. Commercial logging changes the age structure of forests so that the average age of trees is much younger," it said.

"The carbon stock of forests subject to commercial logging, and of monoculture plantations in particular, will therefore always be significantly less on average than the carbon stock of natural, undisturbed forests."

Preventing further deforestation of southeast Australia's eucalypt forests was the equivalent of preventing emissions of 460 million tons of carbon dioxide a year for the next 100 years, scientists said.

Letting logged forests regrow to their natural carbon storage capacity would avoid emissions of 136 million tons of carbon dioxide a year for the next 100 years -- about 25 percent of Australia's total emissions in 2005.

The report says that in Australia, and probably globally, the carbon carrying capacity of natural forests is underestimated and therefore misrepresented in economic valuations and in policy options.

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On the Net:

• Australian National University
• Intergovernmental Panel on Climate Change

Source: redOrbit Staff & Wire Reports

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