by Allan Britnell

Most of us have known for years that trees are good for the environment, particularly because of their ability to sequester greenhouse gases spewed by cars and the other conveniences of our lives. Yet, until recently, no one knew precisely just how much carbon forests could store. But a detailed analysis published in the August 19, 2011, issue of the journal Science has cleared the air on how significant a factor forest-carbon capture is.

The study, which analyzed forest inventory figures from countries around the globe and grouped them according to temperate, tropical and boreal regions, estimates that forests cumulatively sequester approximately 2.4 billion tonnes of carbon every year. That means that trees capture nearly one-third of the estimated 8.8 billion tonnes of carbon dioxide emitted annually.

“This study clearly indicates the important role that forests play in absorbing carbon and regulating the climate,” says Anne

Bell, Ontario Nature’s director of conservation and education. “The science is complex, and there are many uncertainties, but of note is the finding that, globally, the net forest carbon sink is mainly in the temperate and boreal forests.”

That is in part because the carbon released from the ongoing deforestation in the tropics almost entirely negated the amount sequestered in patches of undisturbed tropical forest. One saving grace for the region was the surprisingly high level of carbon capture – 1.6 billion tonnes – of forest regrowth following logging and slash and- burn operations.

Closer to home, the researchers also came to some troubling conclusions. Over the course of the two time periods studied,

1990 to 1999 and 2000 to 2007, the biomass of Canadian forests actually decreased by half, primarily as a result of losses to forest fires and damage from invasive species.