Carbon is driving unexpected growth in Amazon’s giant trees

The Amazon rainforest is often described as the “lungs of the planet.” Stretching across nine nations, it provides shelter to millions of species and stores vast amounts of carbon. Yet, amid concerns about climate change and deforestation, new research has revealed a surprising discovery: the trees themselves are growing larger.

A new study published in the journal Nature Plants reveals that the average size of trees across the Amazon has increased by 3.2 percent per decade.

This remarkable trend, observed consistently for at least 30 years, reflects the forest’s response to rising carbon dioxide levels.

Forest giants keep expanding

The findings come from an international partnership of more than 60 universities, including institutions in South America and the UK, such as the Universities of Birmingham, Bristol, and Leeds. This large-scale collaboration allowed scientists to gather a comprehensive picture of tree growth across diverse regions of the Amazon.

Nearly one hundred researchers monitored tree growth in 188 permanent plots. Their collective data showed that trees – both large and small – have grown steadily larger.

“This is a good news story,” said Professor Beatriz Marimon from Universidade do Mato Grosso, who coordinated much of the Brazilian data collection. “We regularly hear how climate change and fragmentation is threatening Amazonian forests.”

“But meanwhile the trees in intact forests have grown bigger; even the largest trees have continued to thrive despite these threats.”

Carbon impact on Amazon trees

The study highlights that increased atmospheric carbon dioxide is fueling tree growth, acting like a fertilizer for the forest. Large trees in particular play a critical role by absorbing vast amounts of carbon from the atmosphere.

“Ahead of COP30 in Brazil later this year, these results underscore just how important tropical rainforests are in our ongoing efforts to mitigate against climate change,” said joint lead author Dr. Adriane Esquivel-Muelbert of the University of Cambridge.

Large trees remain highly effective at absorbing CO₂ from the atmosphere, and despite concerns that climate change could weaken this ability in the Amazon, this research shows that the growth-stimulating effect of CO₂ persists – highlighting the remarkable resilience of these forests, at least for now.

Old giants hold unique power

While the growth of trees brings positive news, the research also warns of significant risks. Large trees, many hundreds of years old, provide unique carbon and biodiversity benefits that cannot be replaced quickly.

“Our paper also highlights how destructive Amazon deforestation really is,” said Dr. Rebecca Banbury Morgan from the University of Bristol.

“Large tropical trees are hundreds of years old. We can’t simply plant new trees and expect them to confer anything like the kinds of carbon or biodiversity benefits that the old, natural forest is providing.”

Growth reshapes the whole forest

The RAINFOR network has previously shown that intact Amazonian forests store more carbon over time. This study extends that knowledge by demonstrating not only that carbon storage has increased, but also that trees of all sizes have grown larger across the forest.

“We knew that the total amount of carbon stored in the trees of intact Amazonian forests has increased,” said Professor Tim Baker of the University of Leeds, a senior author.

“What this new study shows is that all sizes of tree have grown larger over the same period – the whole forest has changed.”

Big trees need a connected forest

As trees expand in size, the largest individuals increasingly dominate resources, shaping the forest structure. Their survival, however, depends on the resilience of the ecosystem as a whole.

“What happens to big trees – including how they deal with increasing climate threats and manage to disperse their seeds – is now mission-critical,” said Professor Oliver Phillips of the University of Leeds.

“The only way the giants will stay healthy is if the Amazon ecosystem stays connected. Deforestation is a huge threat-multiplier and will kill them if we let it.”

Carbon gains for Amazon trees

The research paints a picture of both resilience and fragility. Amazon trees are adapting to higher carbon dioxide levels by growing larger, enhancing their role in carbon storage.

Yet, this resilience is under constant threat from deforestation and climate pressures. The message is clear: protecting the forest as a connected system remains vital if these gains are to continue.

The study is published in the journal Nature Plants.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–