Marlowe Hood Yahoo News 16 Apr 09;
PARIS (AFP) – Forests that today soak up a quarter of carbon pollution spewed into the atmosphere could soon become a net source of CO2 if Earth's surface warms by another two degrees Celsius (3.6 degrees Fahrenheit), cautions a report to be presented Friday at the UN.
Plants both absorb and exhale carbon dioxide, but healthy forests -- especially those in the tropics -- take up far more of the greenhouse gas than they give off.
When they are damaged, get sick or die, that stored carbon is released.
"We normally think of forests as putting the brakes on global warming," said Risto Seppala, a professor at the Finnish Forest Research Institute and head of the expert panel that produced the report.
"But in fact over the next few decades, damage induced by climate change could cause forests to release huge quantities of carbon and create a situation in which they do more to accelerate warming than slow it down."
Authored by 35 of the world's top forestry scientists, the study provides the first global assessment of the ability of forests to adapt to climate change.
Manmade warming to date -- about 0.7 C since the mid-19th century -- has already slowed regeneration of tropical forests, and made them more vulnerable to fire, disease and insect infestations. Increasingly violent and frequent storms have added to the destruction.
If temperatures climb even further, the consequences could be devastating, according to the report by the Vienna-based International Union of Forest Research Organisations (IUFRO).
"The current carbon-regulating functions of forests are at risk of being lost entirely unless carbon emissions are reduced drastically," said Alexander Buck, IUFRO's deputy director and coordinator of the report.
"With a global warming of 2.5 C (4.5 F) compared to pre-industrial times, the forest ecosystems would begin to turn into a net source of carbon, adding significantly to emissions from fossil fuels and deforestation," he told AFP by phone.
The UN's Intergovernmental Panel on Climate Change (IPCC) predicted in 2007 that average global temperatures would go up before 2100 by 1.1 C to 6.4 C (2.0 F to 11.5 F), depending on efforts to curb the gases that drive global warming.
Any increase of more than 2.0 C, the panel said, would unleash a maelstrom of human misery, including drought, famine, disease and forced migration.
Since the IPCC report, however, a growing number of climate scientists have said that this threshold is likely to be crossed no matter what actions are taken.
The forest assessment did contain what appears to be some good news: cold-clime boreal forests stretching across vast expanses of Russia, northern Europe, Canada and Alaska are set to expand rapidly as climate change kicks in.
But while this may be a boon for the timber industry, it is not likely to help curb global warming, it said.
"One might assume with the increasing growth in boreal forests that more carbon would be taken up by forest ecosystems and removed from the atmosphere," said Buck.
"But these positive effects will be clearly outweighed by the negative impacts on forest ecosystems."
The report urged international negotiators trying to hammer out a new global climate change treaty before the end of the year to take into account the potential impact of warming on forests.
Up to now, discussions on forests at the UN climate talks have focused almost exclusively on the impact of deforestation.
The destruction of vegetation straddling the equator -- some 130,000 square kilometers (50,000 square miles) disappear every year -- accounts for nearly 20 percent of total carbon emissions.
"But it is also important to keep in mind that those forests that remain will be affected by climate change to a degree that might exceed their capacity to adapt," Buck cautioned.
The IUFRO report will be submitted to the UN Forum on Forests.
Forests could become source of warming: report
Timothy Gardner, Reuters 17 Apr 09;
NEW YORK (Reuters) - The world's forests are at risk of becoming a source of planet-warming emissions instead of soaking them up like a sponge unless greenhouse gases are controlled, scientists said.
Deforestation emits 20 percent of the world's carbon dioxide when people cut and burn trees, but standing forests soak up 25 percent of the emissions.
If the Earth heats up 2.5 degrees Celsius (4.5 degrees F) or more, evaporation from the additional heat would lead to severe droughts and heat waves that could kill wide swaths of trees in the tropics of Africa, southern Asia and South America. And emissions from the rotting trees would make forests a source of global warming.
"If temperatures are growing at the current pace definitely this would happen at the end of this century or before," said Risto Seppala, chair of a report by the International Union of Forest Research Organizations, a nonprofit network of scientists.
The IUFRO will present the report to the U.N.'s Forum on Forests in New York next week.
Not all areas of the world would suffer immediately and pine forests in northern parts of the world could benefit at first.
"In the beginning it would mean some very positive consequences," for boreal forests such as those found in Northern Europe and Canada, said Seppala by telephone from his home in Finland north of the Arctic Circle. He said timber and paper industries in the North could prosper as warmer weather pushes growth of spruce and other trees.
Even forests found in more temperate parts of the world, such as the United States and Western Europe, could grow faster at first.
"Those who live in industrialized countries in the Northern Hemisphere won't suffer too much at first," he said.
People in many developing countries with forests tend to rely more on forests for food, clean water and other basic needs.
But eventually tree pests and parasites that until now have not appeared much in forests in colder parts of the world are likely to spread north as temperatures warm, the report said.
An example of pests already moving to the North is the pine beetle, which has devastated large parts of forests in British Columbia over the past decade and has moved into the province of Alberta. The pest can be killed by periods of extreme cold, but the 2007-2008 winter did not kill off the insects in Alberta.
Much depends on exactly how much temperatures will warm. A Reuters poll earlier this month of scientists showed that global warming is like to overshoot a 2 degrees Celsius (3.6 F) rise above pre-industrial levels seen by many countries as the maximum to avoid the worst of rising sea levels, floods, droughts and heat waves. Temperatures have already risen 0.7 Celsius.
Steps can be taken to protect forests and help them adapt to warmer temperatures, such as sustainable harvesting, the IUFRO report said. Perhaps even more important is cutting global emissions of greenhouse gases, said Seppala.
(Editing by Christian Wiessner)
