April 17, 2009

Forest Carbon Sinks Threatened By Global Warming

The Earth's forests serve as crucial carbon sinks due to their ability to absorb greenhouse gases, but that ability is "at risk of being lost entirely", according to a new United Nations report.

Currently, the Earth's forests soak up about 25 percent of greenhouse gas emissions, but that capability could be reversed if the Earth heats up 2.5 degrees Celsius (4.5 degrees F) more.

A rise in temperature could cause severe droughts and heat waves that would kill off many of the Earth's forests in Africa, southern Asia and South America, thus reducing their ability to soak up emissions.

The new report, "Adaptation of Forests and People to Climate Change "“ A Global Assessment", was put together by the Vienna-based International Union of Forest Research Organizations (IUFRO) through the Collaborative Partnership on Forests (CPF), an alliance of 14 international organizations that each has substantial forestry programs.

The report, authored by 35 of the world's top forestry scientists, offers the first depiction of how the world's forests would react to a rise in global temperature.

"We normally think of forests as putting the brakes on global warming," said Risto Seppala, a professor at the Finnish Forest Research Institute (Metla) and Immediate Past President of IUFRO, who chaired 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 to slow it down."

Deforestation currently amounts to 20 percent of the world's carbon dioxide emissions. If the forests began to die out due to a rise in temperature, all of the absorbed carbon would be released into the atmosphere and intensify the rate of global warming, scientists said.

"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.

Higher temperatures, along with prolonged droughts, intense pest invasions, and other environmental stresses could add more risks to the threat of forest decline, according to scientists.

"If temperatures are growing at the current pace definitely this would happen at the end of this century or before," said Seppala.

"In the beginning it would mean some very positive consequences," for boreal forests such as those found in Northern Europe and Canada, Seppala told Reuters. He said paper companies in the North would initially benefit from the extra growth of spruce trees caused by warmer weather.

"Those who live in industrialized countries in the Northern Hemisphere won't suffer too much at first," he said.

But "decreased rainfall and more severe droughts are expected to be particularly stressful for forest-dependent people in Africa who look to forests for food, clean water and other basic needs," scientists said.

Scientists plan to officially present the new report at the UN's Forum on Forests in New York City next week. It is their hope that the new report will help gather more support to shape new international climate change policy in the months leading up to the conference in Copenhagen in December.

"Even if adaptation measures are fully implemented, unmitigated climate change would, during the course of the current century, exceed the adaptive capacity of many forests," said Professor Andreas Fischlin of the Swiss Federal Institute of Technology, who is one of the lead authors of the study and a coordinating lead author with the IPCC.

"The fact remains that the only way to ensure that forests do not suffer unprecedented harm is to achieve large reductions in greenhouse gas emissions."


Image 1: Efforts to manage tropical forests more sustainably must take into account the complex relationships between the welfare of local people and global concerns such as climate change. Credit: Photo: John Innes

Image 2: A series of warmer-than-average winters have allowed populations of the Spruce Beetle (Dendroctonus rufipennis) to develop, resulting in the mortality of almost 400,000 ha of this boreal forest. Credit: Photo: John Innes


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