Australia's forests key to fighting global warming

Rob Taylor, Reuters 16 Jun 09;

CANBERRA (Reuters) - Ancient Australian forests are key to fighting climate change and contain the world's most dense carbon store, eclipsing tropical rainforests as efficient greenhouse gas absorbers, scientists said on Tuesday.

Towering Mountain Ash forests covering Victoria state's cool highlands hold four times more carbon, or around 1,900 metric tons of carbon per hectare, than tropical forests, scientists at the Australian National University said.

"The trees in these forests can grow to a very old age, at least 350 years, and they can grow very large, very tall, and they grow very dense, heavy wood," said Brendan Mackey, a professor of environment science.

The researchers studied biomass data from 132 forests around the world to discover regions storing the most carbon, with results published in the U.S.-based Proceedings of the National Academy of Sciences.

The Australian forest was compared to old growth tracts on the United States Pacific Coast, Siberia, the central Amazon, Thailand and Cambodia, Venezuela, Finland and elsewhere.

The findings overturn conventional thinking about the carbon density of different forest types that until now held that tropical rainforests were the most carbon-dense, Mackey said.

The Victorian forest, part of the water catchment for Australia's second biggest city Melbourne, was a large store because the area had been protected from logging, highlighting the link between old growth forest felling and global warming.

"Part of the reason these trees store so much is that they have reached mature growth. You are just never going to store the same amount of carbon if you are turning the forest over every 40 years," Mackey told Reuters.

"This reinforces the point that we need to think about the carbon value of these forests, which we've just been thinking of until now as wood supply," he said.

A second reason for Mountain Ash's carbon efficiency was that plant growth rates were balanced by rates at which biomass decayed, with the cool Victorian forests conducive to high growth and slower rates of decomposition.

That placed Australia's living and dead biomass carbon among Mountain Ash forest at 1,900 metric tons per hectare against 650 tones per hectare in temperate U.S. Pacific forests and between 140 and 250 metric tons in most rainforests globally.

The Victorian forests are in rugged mountains at the head of the Yarra River, which eventually flows through the center of Melbourne, and is surrounded by national park and state forest.

Mackey said the findings could be of real help in planning the fight against climate change in other parts of the world.

"If we were to have climate change policies that recognized the mitigation value of the carbon stocks in natural forest, then that would give a completely different set of values about forest resource management," he said.

Australia's Wilderness Society said the carbon stored in the native forests of Southeast Australia was equivalent to 460 million metric tons of greenhouse gas per year for the next 100 years, with 9.3 billion metric tons of carbon stored.

"This research demonstrates how important it is for the (national) government to now take seriously the carbon stored in our remaining native forests," said Virginia Young, the society's Strategic Campaigns Coordinator.

(Editing by Sanjeev Miglani)