Alister Doyle, PlanetArk 11 Sep 08;
OSLO - Old forests from Alaska to Russia soak up vast amount of greenhouse gases as they age and are wrongly overlooked as a weapon in a UN-led fight against global warming, a study said on Wednesday.
"New growth continues in forests that are centuries old," an international team of scientists wrote in the journal Nature of old forests outside the tropics that make up 15 percent of the world's total tree-covered area.
Plants soak up heat-trapping carbon from the air as they grow and release it when they die. Until now, most scientists have reckoned that mature forests have a neutral impact on the climate, with any new trees merely replacing others that die.
The report, by scientists in Belgium, the United States, Germany, Switzerland, France and Britain, estimated that old-growth forests outside the tropics absorbed a net 1.3 billion tonnes of carbon a year with ever denser vegetation.
That is almost as much as the total annual industrial greenhouse gas emissions by the 27-nation European Union.
"Until now there was a belief that ecosystems -- like weeds, bacteria in a pond or forests -- reach carbon neutrality when they age," lead author Sebastiaan Luyssaert of the University of Antwerp told Reuters.
"We find no support for that idea," he said. The scientists urged greater protection for temperate forests and northern pine forests such as in Siberia, Canada, the Nordic region or Canada.
The forests studied, from 15 to 800 years old, kept on growing thicker roots and branches while carbon-rich leaves and other debris built up in the soil. And new vegetation quickly replaced fallen trees that could take decades to rot.
REDWOOD LIMIT
Still, forests could not go on absorbing more carbon for ever. Forests along the Pacific coast of the United States, where giant redwoods flourish, seemed at the limit with between 500 and 700 tonnes of carbon per hectare (2.5 acres), they said.
And the scientists said there was too little data to know if tropical forests, less affected by seasonal swings and other factors, also kept accumulating carbon as they aged.
Deforestation, often burning of forests to clear land for farming, accounts for 20 percent of greenhouse gas emissions from human sources, according to UN data. Warming can stoke droughts, heatwaves, more powerful storms and rising seas.
Climate negotiators from 190 nations, meant to agree a new UN pact to fight global warming by the end of 2009, are debating ways to pay developing nations to slow deforestation from Brazil to Indonesia.
The Nature study urged wider protection for other forests and said that: "carbon-accounting rules for forests should give credit for leaving old-growth forest intact."
"The focus on deforestation has been limited to the tropics," Luyssaert said. "We kind of forgot about the forests in places like Siberia, Canada and Alaska. Hopefully we can draw attention to them."
(Editing by Matthew Jones)
Old forests help curb global warming too: study
Yahoo News 10 Sep 08;
Old-growth forests remove carbon dioxide (CO2) from the atmosphere, helping to curb the greenhouse gases that drive global warming, according to a study to be published Thursday.
Many environmental policies are based on the assumption that only younger forests, mainly in the tropics, absorb significantly more CO2 than they release.
Partly as a result, primary forests in temperate and subarctic regions of the northern hemisphere are not protected by international treaties, and do not figure in climate change negotiations seeking ways to reward countries that protect carbon-absorbing woodlands within their borders.
Some 30 percent of global forest area -- half old-growth -- is unmanaged primary forest.
"Old-growth forests can continue to accumulate carbon, contrary to the long-standing view that they are carbon neutral," lead researcher Sebastiaan Luyssaert, a professor at the University of Antwerp in Belgium, told AFP.
An international team led by Luyssaert analysed scores of databases set up to monitor the flow of carbon into and out of the world's vegetal ecosystems.
They calculated that primary forests in Canada, Russia and Alaska alone absorb about 1.3 gigatonnes of carbon per year, about ten percent of the net global carbon exchange between the ecosystem and the atmosphere.
These forests need to be protected not just because they help to absorb carbon dioxide, but also because destroying them could release huge stores of greenhouse gases.
"Old-growth forests accumulate carbon for centuries and contain large quantities of it," Luyssaert said. If these pools of CO2 "are disturbed, much of this CO2 will move back into the atmosphere," he added.
The new study, published in the London-based science journal Nature, suggests that UN climate change negotiations underway should also include incentives for northern hemisphere countries to protect their forests.
"The discussions should be expanded to include boreal and temperate forests in Canada and Russia," Luyssaert said.
