For years, scientists believed that boreal forests—the vast stretches of coniferous trees covering regions like Canada and Siberia—were the world’s most effective carbon sinks.
These forests were thought to be doing the heavy lifting when it came to pulling carbon dioxide (CO₂) out of the atmosphere, helping slow the rate of global warming.
But a groundbreaking study by NASA researchers has just flipped that assumption on its head.
According to their findings, tropical forests are actually absorbing far more CO₂ than boreal forests—1.4 billion metric tonnes out of a total of 2.5 billion.
This means that rainforests, not northern pine forests, are Earth’s best defense against climate change.
“This is good news, because uptake in boreal forests is already slowing, while tropical forests may continue to take up carbon for many years,” said lead author David Schimel of NASA’s Jet Propulsion Laboratory.
In a world where carbon emissions continue to rise, this discovery is both surprising and critically important.
But it also raises an uncomfortable question: Are we doing enough to protect these forests?
The Surprising Science Behind CO₂ Absorption
It’s no secret that forests play a crucial role in fighting climate change.
Through photosynthesis, trees absorb about 30% of human-produced CO₂, preventing it from lingering in the atmosphere and accelerating global warming.
But accurately measuring how much CO₂ forests absorb—and which forests are doing the most work—is incredibly difficult.
“Feedbacks from terrestrial ecosystems to atmospheric CO₂ concentrations contribute the second-largest uncertainty to projections of future climate,” the researchers wrote in the Proceedings of the National Academy of Sciences.
Simply put, figuring out where all this carbon is going isn’t easy.
Scientists have to rely on a mix of:
- Satellite imagery, which tracks changes in forest cover
- Experimental forest plots, where researchers measure tree growth and CO₂ absorption
- Computer models, which simulate atmospheric and ecological processes
By combining these methods, NASA scientists were able to trace how CO₂ moves through Earth’s atmosphere and into different ecosystems.
The results were striking: Tropical forests were absorbing more CO₂ than previously estimated—more than any other forest type on Earth.
“Until our analysis, no one had successfully completed a global reconciliation of information about carbon dioxide effects from the atmospheric, forestry, and modeling communities,” said co-author Joshua Fisher.
So, why are tropical forests outperforming boreal forests?
The answer lies in a process called carbon fertilization—and it turns out human activity is actually making forests grow faster.
Are We Accidentally Supercharging Rainforest Growth?
It might sound counterintuitive, but in one specific way, rising CO₂ levels are actually helping forests grow.
This process, known as carbon fertilization, occurs because plants need CO₂ to perform photosynthesis.
As humans pump more of this greenhouse gas into the air, forests are getting an unexpected boost—they’re growing faster and absorbing more carbon in the process.
Interestingly, this effect appears to be strongest in warmer climates, which could explain why tropical forests are outpacing boreal forests in carbon absorption.
“What we’ve had up till this paper was a theory of carbon dioxide fertilization based on phenomena at the microscopic scale and observations at the global scale that appeared to contradict those phenomena,” Schimel explained.
“Here, at least, is a hypothesis that provides a consistent explanation that includes both how we know photosynthesis works and what’s happening at the planetary scale.”
So, in a bizarre twist, our fossil fuel emissions may have accidentally supercharged the ability of tropical forests to absorb CO₂—at least for now.
But before you get too optimistic, there’s a catch.
Why Tropical Forests Are at Risk
Yes, tropical forests are pulling more CO₂ out of the air than we thought.
But at the same time, they’re facing unprecedented threats—and those same forests could soon become a net source of CO₂ instead of a sink.
Here’s why:
- Deforestation is accelerating. The Amazon rainforest alone loses an area the size of New York City every month due to illegal logging, agriculture, and land clearing.
- Fires—both natural and human-caused—are increasing. Wildfires and slash-and-burn deforestation send enormous amounts of carbon back into the atmosphere, counteracting any CO₂ absorption gains.
- Climate change is making forests less resilient. Higher temperatures and shifting rainfall patterns are causing more tree die-offs and reducing the forests’ ability to absorb carbon.
If this trend continues, we could soon reach a dangerous tipping point.
Instead of slowing climate change, rainforests could actually start accelerating it.
As Schimel and his team point out, losing these forests would be catastrophic.
Protecting Rainforests Is Now More Urgent Than Ever
For decades, the fight against climate change has largely focused on reducing emissions—which is, of course, essential.
But this new research highlights a critical second piece of the puzzle: protecting the carbon sinks that are already working to clean up our mess.
If tropical forests are doing more of the heavy lifting than we thought, then we need to double down on conservation efforts.
That means:
Cracking down on illegal logging and deforestation
Investing in rainforest restoration projects
Supporting sustainable land-use practices
Holding corporations accountable for environmental destruction
The good news?
Unlike other solutions to climate change, this one already exists.
We don’t need futuristic carbon-capture technology or experimental geoengineering—we just need to keep the world’s forests standing.
Because as this NASA study makes clear: The fate of our climate may depend on it.
