Skip to main content

Sign up for our newsletter.

Quality journalism. Progressive values. Direct to your inbox.

Amazon forest canopy at dawn in Brazil.

Amazon forest canopy at dawn in Brazil. (Photo: Peter Vander Sleen)

'Alarming': Tropical Forests in Shift From Carbon Sponge to Carbon Source

"We've found that one of the most worrying impacts of climate change has already begun."

Andrea Germanos

A new study published Wednesday adds to mounting evidence that the world's tropical forests could soon stop serving their climate crisis-mitigating role of carbon sinks.

"After years of work deep in the Congo and Amazon rainforests, we've found that one of the most worrying impacts of climate change has already begun. This is decades ahead of even the most pessimistic climate models," said Simon Lewis, a senior author of the study and a professor from the School of Geography at the U.K.'s University of Leeds.

"There is no time to lose in terms of tackling climate change," said Lewis.

The findings, published in the journal Nature, represent the collaborative effort of roughly 100 institutions in which researchers tracked some 300,000 trees spanning 565 patches of undisturbed tropical forests across Africa and the Amazon over a 30-year period.

Researchers used measurements of tree growth and death, along with CO2 emissions, rainfall, and temperatures, to estimate carbon storage or "sequestration."

"We show that peak carbon uptake into intact tropical forests occurred in the 1990s," said lead author Wannes Hubau of the Royal Museum for Central Africa in Belgium.

At that time, the forests were able to store 46 billion tonnes of CO2 from the atmosphere, representing about 17% of human-made carbon dioxide emissions.

Fast forward to the 2010s, and the researchers found the amount dropped to an estimated 25 billion tonnes, on par with roughly 6% of human-made carbon dioxide emissions.

Over the 30 years, the area of intact forest shrunk by 19% but global carbon dioxide emissions soared by 46%, the researchers noted.

The downward trend of carbon absorption didn't happen in the zones at the same time, the study also found. The downward trend of sequestration hit the Amazon in the mid-1990s and the African forests about 15 years later.

The potential for the Amazon forests to switch from carbon sink to carbon source isn't far off, with the study predicting it could happen as soon as the mid-2030s.

Hubau, in his statement, stressed need for ongoing monitoring "as our planet's last great tropical forests are threatened as never before."

For the moment, at least, humanity should still consider tropical forests carbon sponges. But, if urgent and bold measures aren't taken soon, that could well change.

"Intact tropical forests remain a vital carbon sink but this research reveals that unless policies are put in place to stabilize Earth's climate it is only a matter of time until they are no longer able to sequester carbon," said Lewis, pointing to the possibility of a feedback loop being triggered.

"One big concern for the future of humanity is when carbon-cycle feedbacks really kick in, with nature switching from slowing climate change to accelerating," Lewis said.

The bottom line for global governments is clear.

"By driving carbon dioxide emissions to net-zero even faster than currently envisaged, it would be possible to avoid intact tropical forests becoming a large source of carbon to the atmosphere. But that window of possibility is closing fast," said Lewis.

Professor Douglas Sheil at the Norwegian University of Life Sciences, a contributing researcher to the study, put the findings in stark terms.

"Our results are alarming," he said.

"The word 'alarming' should not be used lightly," continued Sheil, "but in this case it fits."


Our work is licensed under Creative Commons (CC BY-NC-ND 3.0). Feel free to republish and share widely.

We've had enough. The 1% own and operate the corporate media. They are doing everything they can to defend the status quo, squash dissent and protect the wealthy and the powerful. The Common Dreams media model is different. We cover the news that matters to the 99%. Our mission? To inform. To inspire. To ignite change for the common good. How? Nonprofit. Independent. Reader-supported. Free to read. Free to republish. Free to share. With no advertising. No paywalls. No selling of your data. Thousands of small donations fund our newsroom and allow us to continue publishing. Can you chip in? We can't do it without you. Thank you.

Biden Urged to Fire Covid Response Chief Over 'Damning' Failures

"Zients has failed to provide the materials necessary to improve the U.S. response, or the guidance necessary to keep the pandemic under control," argued one critic.

Jake Johnson ·


As Sinema Defends Filibuster, Progressives Say 'Vote Her the Hell Out'

"The filibuster is a meaningless Senate rule. It's a remnant of slavery used to block civil rights for generations."

Jake Johnson ·


Poor People's Campaign Readies 'Massive, Nonviolent' Effort to Save Democracy

"We are not in this for a moment, but for a movement," said Rev. Dr. William J. Barber II. "Our deadline is victory."

Jake Johnson ·


Tsunami Triggered by Huge Volcanic Eruption Hits Tonga

The undersea volcano's eruption also sparked tsunami warnings for Fiji, Samoa, New Zealand, and the West Coast of the United States.

Common Dreams staff ·


Sanders Says Manchin and Sinema Are Imperiling US Democracy

"It is a sad day when two members of the Democratic Caucus are prepared to allow the Freedom to Vote Act to fail and undermine the future of American democracy."

Jake Johnson ·

Support our work.

We are independent, non-profit, advertising-free and 100% reader supported.

Subscribe to our newsletter.

Quality journalism. Progressive values.
Direct to your inbox.

Subscribe to our Newsletter.


Common Dreams, Inc. Founded 1997. Registered 501(c3) Non-Profit | Privacy Policy
Common Dreams Logo