Untouched forests store 3 times more carbon: study

SYDNEY (Reuters) - Untouched natural forests store three times more carbon dioxide than previously estimated and 60 percent more than plantation forests, said a new Australian study of "green carbon" and its role in climate change.

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.

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

"In Australia and probably globally, the carbon carrying capacity of natural forests is underestimated and therefore misrepresented in economic valuations and in policy options," said the scientists in their report released on Tuesday.

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

Yet 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.

The IPCC defines a forest as trees taller than 2 meters (six feet) and a canopy cover greater than 10 percent, but in Australia a forest was defined as having trees taller than 10 meters (33 feet) and a canopy cover greater than 30 percent.

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

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

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

"MORE RESILIENT"

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.

Co-author of the report Brendan Mackey said protecting natural forests served two purposes: it maintained a large carbon sink and stopped the release of the forest's stored carbon.

The carbon stored in the world's biomass and soil was approximately three times the amount in the atmosphere, said the report. 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.

The report said 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.

Mackey said emissions trading systems should not favor plantation forests as carbon offsets, as they would not balance out the loss of natural forests and release of carbon.

"We need to make sure that emissions trading schemes do not lead to perverse outcomes," Mackey told Reuters. Australia has promised to introduce an emissions trading system by 2010, but it will exclude agriculture.

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

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

Australian Greens political party called on Prime Minister Kevin Rudd to end old-growth logging in Australia and lead the world in protecting natural forests at the U.N. Climate Change Conference in Copenhagen in 2009.

In Copenhagen, world nations are expected to agree on a broader pact to replace the Kyoto Protocol. The new pact would bind all countries to emissions curbs from 2013.

"The Rudd government should be leading the charge in Copenhagen to ensure the green carbon in the natural forests of both developed and developing countries are recognized and protected," said Greens leader Bob Brown.

(Editing by David Fogarty)