Healthy forests keep CO2 in check — until temperatures soar

Tropical forests are an overlooked ally in the climate crisis — storing 25 years worth of fossil fuel emissions in trees alone.

A new study shows these forests continue to store this carbon. If global temperatures continue to rise, however, they could release stored carbon and cause a cycle of accelerated climate change.

Christopher Baraloto and researchers from the FIU Institute of Environment, were a part of an international research team that conducted the first study to analyze long-term climate sensitivity data from more than 500,000 trees in 813 forests across the tropics.

They found these forests continue to store high levels of carbon up to an estimated threshold of 89.6 degrees Fahrenheit in daytime temperature. Anything above this puts forests in a danger zone. Even a two degree increase above the threshold would release four times as much carbon dioxide than would have been released.

“There is a message of hope with this study,” Baraloto said. “These forests are relatively resilient and are now predicted to withstand a moderate level of temperature increase based on our measurements and models.”

Tropical forests have the ability to adapt to some climate change, partly because of their high biodiversity. Species that thrive in warming temperatures replace those that can’t handle warming temperatures. Ensuring forests can continue to store carbon means giving these trees time to grow and protecting them from fire and other threats. 

“We must take this as a warning to limit deforestation and other activities linked to global temperature increases, so as to maintain these forests, which are vital to our planet’s health and our security,” Baraloto said.

The insights into how the world’s tropical forests respond to climate were only possible with decades of careful fieldwork, often in remote locations. The global team of 225 researchers combined forests observations across South America (RAINFOR), Africa (AfriTRON) and Asia (T-FORCES). In each monitoring plot, the diameter of each tree and its height was used to calculate how much carbon they stored. Plots were revisited every few years to see how much carbon was being taken in and how long it was stored before trees died.

Calculating changes in carbon storage required identifying nearly 10,000 tree species and more than 2 million measurements of tree size across 24 tropical countries.

The research team points out that reducing carbon emissions is key to keeping forests healthy.

“Right now, humanity has a unique opportunity to make the transition toward a stable climate. By not simply returning to ‘business as usual’ after the current crisis we can ensure tropical forests remain huge stores of carbon,” Oliver Phillips of the University of Leeds, the study’s senior author, said. “Imagine if we take this chance to reset how we treat our Earth. We can keep our home cool enough to protect these magnificent forests - and keep all of us safer.”

The findings were published today in Science.