Instead of absorbing carbon dioxide from the air, tropical rainforests could become a source of carbon in the atmosphere as soon as the next decade. Long appreciated as “carbon sinks,” those days will soon be over, according to a new study published in the journal Nature.

“We’ve found that one of the most worrying impacts of climate change has already begun,” Simon Lewis, study author and plant ecologist at University of Leeds, told The Guardian. “This is decades ahead of even the most pessimistic climate models.”

Researchers spent 30 years tracking 300,000 trees in African and Amazonian rainforests. Their work took them to remote sites, and even required a week in a dugout canoe traveling deep into the Democratic Republic of the Congo. The team tagged individual trees with aluminum nails, charting their height and diameter every few years and calculating the carbon stored in both the surviving trees and those that died. The Amazonian forests — which face higher temperatures and worse droughts — were weakening first, but the African forests weren’t far behind. The researchers based their projections that the forests will soon turn into carbon sources on a statistical model, their own observations and trends in emissions, rainfall and temperatures to predict how forests will store carbon in the near future.

Carbon uptake by tropical forests peaked in the 1990s. Back then, the forests absorbed about 17% of the carbon dioxide humans generated. But droughts, deforestation and high temperatures have adversely effected these carbon sinks. By last decade, forests could only take about 6% of global emissions off our hands.

“Humans have been lucky so far, as tropical forests are mopping up lots of our pollution, but they can’t keep doing that indefinitely,” Lewis said. “We need to curb fossil fuel emissions before the global carbon cycle starts working against us. The time for action is now.”

+ Nature

Via The Guardian and Phys.org

Image via Etienne Delorieux