World’s Forests Losing Their Green. Billions of tonnes of CO2 Released
By Stephen Leahy
UXBRIDGE, Canada, Feb 3, 2011 (IPS)
Last year’s severe drought in the Amazon will pump billions of tonnes of additional carbon dioxide (CO2) into the atmosphere, a new report has found.
Researchers calculate that millions of trees died in 2010, which means the Amazon is soaking up much less CO2 from the atmosphere, and those dead trees will now release all the carbon they’ve accumulated over 300 or more years.
The widespread 2010 drought follows a similar drought in 2005 which itself will put an additional five billion tonnes of CO2 into the atmosphere, Simon Lewis of University of Leeds in the UK and colleagues calculate in a study published Thursday in Science. The United States emitted 5.4 billion tonnes of CO2 from fossil fuel use in 2009.
The two droughts will end up adding an estimated 13 billion tonnes of additional CO2 – equivalent to combined emissions in 2009 from China and the U.S. – and likely accelerating global warming.
“New growth in the region will not offset those releases,” Lewis told IPS.
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After the 2005 drought, Lewis and Brazilian scientist Paulo Brando from the Amazon Environmental Research Institute (IPAM) led teams of researchers on the ground to assess the impacts. They determined that only a few trees died per hectare, and so while the forest canopy cover looked relatively unchanged, there had been a significant change in the forest’s carbon balance.
Most years, the Amazon absorbs about 1.5 billion tonnes of CO2 from the atmosphere. This is crucial in helping to offset some of CO2 emissions from burning fossil fuels that is overheating the planet.
However, researchers found during and after the 2005 drought that the Amazon stopped absorbing carbon for two years and became a source of CO2 amounting to roughly five billion tonnes over a period of four to eight years as the dead trees rot and release their stored carbon. Lewis and Brando expect something similar with the 2010 drought – but with many more trees killed.
“The 2010 drought was spread over a huge area several million square kilometres in size,” Lewis said.
“Having two events of this magnitude in such close succession is extremely unusual, but is unfortunately consistent with those climate models that project a grim future for Amazonia,” he said in a release.
Those models show a decline in rainfall in much of the region as the climate warms. Most worrying is if these staggeringly large CO2 emissions from droughts become part of a feedback loop of drying out the region even more, leading to more frequent and intense droughts. However, it is too soon to tell if that is underway, Lewis told IPS.
The fact that Amazon may be near a tipping point of unstoppable decline was the warning in a million-dollar study by the world’s leading research institutions IPS reported on a year ago.
The study, “Assessment of the Risk of Amazon Dieback”, found that a combination of climate change, deforestation and fire could lead to the inevitable loss of 66 percent of the current 5.3 million sq km forest by 2075. That means the Amazon would shrink from covering an area the size of the entire continental United States to the state of Alaska.
The rainforest literally makes much of its own rain, but when too much forest cover is lost, this unique feature declines leading to further drying and increased potential for fire, the researchers found. And that leads to even less rain in what becomes a spiral of decline.
“The forest eventually converts to cerrado (the Brazilian savanna) after a lot of fire, human misery, loss of biodiversity and emission of carbon into the atmosphere,” Thomas Lovejoy, biodiversity chair at the Washington DC- based Heinz Centre for Science, Economics and the Environment, told IPS at the time.
“It may happen faster than that study projected given the droughts of 2005 and 2010,” said leading tropical biologist Daniel Nepstad of IPAM in Belem, Brazil.
Over the past four years there has been a 25 percent decline in rainfall in the southeast Amazon, sparking huge fires that cover up to 10,000 sq km, Nepstad told IPS. The smoke from the fires inhibits rainfall, further drying the forests.
“There seems to be a change in the regional climate,” he speculated.
Fortunately, there has been a big decline in deforestation in the Amazon in recent years. “In (the state of) Matto Grosso it has fallen 67 percent,” he said.
Brazilian and state governments get some of the credit, along with falling prices for soy and cattle. Carbon offset programmes like Reduced Emissions from Deforestation and Degradation (REDD) have also silenced the chain saws as land owners and others wait to see if the promised billions of dollars for protecting forests materialises.
“Some REDD money is starting to come in,” Nepstad said. “If we can do REDD right it could have a big impact.”
Nepstad said other forests are also shifting from absorbing CO2 to emitting the global warming gas. A particular worry is the Boreal forest that spans the top of the globe and is much larger than Amazon.
“The Boreal is losing its green, especially in North America, from disease, insect outbreaks and fires,” he said.
There is potential for “huge feedbacks” in the Boreal which has far more carbon stored in it than anywhere else.
“Forests diebacks are taking place all around the world. The evidence is quite sobering,” he said.
This reinforces the urgent need to reduce emissions of fossils fuels and to develop a global land strategy to turn sources of CO2 into sinks for CO2, he said.
“Most of the evidence shows climate change is speeding up. Meanwhile political action on climate is slowing down,” Nepstad added.