The world’s tropical forests – already known as havens for a diversity of beetles and birds – may also protect the planet from runaway global warming by sucking greenhouse gases out of the air, a new study suggests.
Jungles remove one-fourth of human greenhouse-gas emissions every year, according to an international team of scientists led by Britt Stephens at the National Center for Atmospheric Research in Boulder.
“Tropical forests are helping much more than we realized,” Stephens said.
The new study, which appears today in the journal Science, may also solve a scientific mystery that has baffled climate scientists for years, Stephens said: the case of the missing carbon.
Humans generate about 8 billon tons of the greenhouse gas carbon dioxide every year, but scientists could find only about 5.6 billion tons of that in the atmosphere, in the oceans and on land.
Most researchers concluded that northern forests across Canada, Russia and the United States were pulling carbon dioxide out of the atmosphere and putting it into trunks, branches and leaves.
Across much of the Northeastern United States and Europe, forests have been regrowing in the past century as land once once used for farming reverted back into woods, Stephens said.
Most computer models predicted the missing carbon should accumulate in northern lands.
But northern forests haven’t grown fast enough to account for all the missing carbon, according to ground-based measurements – and that has perplexed scientists for more than a decade, said Scott Denning, an atmospheric scientist at Colorado State University in Fort Collins and a co-author of the study.
Stephens, Denning and their colleagues analyzed air samples collected from around the globe by research planes during the past 27 years.
Northern lands take up some carbon, the researchers said – but much more is absorbed in the tropics.
“We’ve basically been looking in the wrong place,” Stephens said.
“This is even a stronger argument for preserving the forests left in the tropics,” said Richard Houghton, a carbon researcher with the Woods Hole Research Center Falmouth, Mass., not involved in the new research.
Houghton said the new paper was “mind-blowing” because its conclusion runs counter to what’s been predicted for two decades, and because it explains once-puzzling ground-based observations.
Some researchers studying small patches of tropical forest found that plants pull carbon dioxide out of the atmosphere, but many scientists dismissed the findings as anomalous and probably not representative of the tropics as a whole.
Staff writer Katy Human can be reached at 303-954-1910 or khuman@denverpost.com.
