World's forests protecting humanity from climate disaster: Study

By Margaret Munro, Postmedia News July 14, 2011 2:23 PM

The world's forests gobble up so much carbon they are protecting the planet from the worst impacts of humans' staggering fossil fuel emissions.

An international study has concluded forests suck up a third of the carbon pumped into the atmosphere each year through the burning of oil, gas and coal.

"That one third taken up by the forests would otherwise be in the atmosphere," said Werner Kurz of the Canadian Forest Service, co-author of the report published Thursday in the journal Science.

The oceans suck up another 20 per cent of the emissions, which means "we have basically been getting a 50 per discount on all our fossil fuel emissions," said Kurz.

The report is the most comprehensive assessment yet of the global forest "sink" and shows trees from the tropics to the boreal play a huge role in controlling the global carbon budget by sucking up vast amounts of carbon from the air and locking it away in wood and soil.

It says that the forests have been a major carbon sink since 1990, and shows the changing dynamics of the world's trees.

It says fire and insects hit this country's forests so hard between 1990 and 2007 that the carbon sink in Canada's managed forest was "reduced by half". On the other side of the Atlantic, the carbon sinks grew in fast-growing new forests in Russia and northern Europe.

The study also highlights the staggering scale of deforestation in the tropics.

Though the world's trees took up close to 4 billion tonnes of carbon a year between 1990 and 2007, the report says almost 3 billion tonnes a year were lost back to the atmosphere because of tropical land clearing and deforestation.

Tally those numbers up and the planet's forests were still a huge carbon sink, despite the deforestation loss — taking up a net 1.1 billion tonnes of carbon a year over the 17-year study period.

The scientists say there is great potential for forests soak up and store more carbon and "lessen the risk of climate change" if deforestation could be reduced in the tropics.

It has long been thought that forests help buffer the planet from the carbon dioxide generated by fossil fuel burning, but the study is the first assessment based on data from thousands of forest sites around the world and remote sensing observations.

It provides a picture of 95 per cent of the world's forests, but notes that data is lacking for some regions like Canada's and Alaska's northern forests. Improving these forest inventories should be a priority, the study says.

While the biggest potential for sequestering more carbon in future is reducing tropical deforestation, which Kurz described as "a tragedy," the study notes there is plenty of carbon-capturing potential in young forests in other regions such as Russia, northern Europe and China.

It says amount of carbon added to Canada's managed forests each year was "reduced by half" over the 17-year study period, largely due to wildfires and insects like the mountain pine beetle that destroyed huge swaths of forest.

The study warns that "relying on biological sequestration is not without risk" since drought and fires can send carbon billowing back into the atmosphere in clouds of smoke.

If the world's forests were to stop acting as sinks then the carbon dioxide level in the atmosphere would "greatly go up," said Kurz, stressing it is "vitally important" to better understand the forces controlling forest carbon uptake and the impact on the global climate system.

"By improving our understanding of where the sinks are geographically, and what is driving them, we have a better ability to predict what they will do in the future," he said.

mmunro@postmedia.com

Twitter.com/margaretmunro

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@VancouverSun World's forests protecting humanity from climate disaster

World's forests protecting humanity from climate disaster: Study

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