Govind Tekale
Amazon rainforest trees have been quietly getting fatter over the past three decades, with their average size increasing by 3.2% every decade, according to a groundbreaking new study published in Nature Plants. This growth appears to be consistent with rising carbon dioxide levels in our atmosphere.
The research, conducted by a team of nearly 100 scientists from over 60 universities worldwide, tracked changes across 188 permanent forest plots throughout the Amazon. Their findings show that trees of all sizes have increased in girth, with the largest trees benefitting the most.
“This is a good news story,” explains Professor Beatriz Marimon from Universidade do Mato Grosso, who helped coordinate 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.”
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The study reveals that the frequency of large trees with trunks over 40 centimeters in diameter has increased by 6.6% per decade. Meanwhile, smaller understory trees declined by more than 1% per decade, indicating a significant shift in forest structure.
This carbon dioxide fertilization effect works because increased CO2 in the air helps trees photosynthesize more efficiently. The trees essentially use this extra carbon to bulk up, building bigger trunks and branches.
Dr. Adriane Esquivel-Muelbert from the University of Cambridge, who led the research, emphasizes the forests’ importance for climate efforts: “Large trees are hugely beneficial for absorbing CO2 from the atmosphere. Despite concerns that climate change may negatively impact trees in the Amazon, the effect of CO2 in stimulating growth is still there. This shows the remarkable resilience of these forests, at least for now.”
However, experts caution that this positive trend comes with important warnings. Dr. Rebecca Banbury Morgan from the University of Bristol points out: “Our paper also highlights how destructive Amazon deforestation really is. 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.”
Professor Oliver Phillips of the University of Leeds adds that keeping the Amazon ecosystem connected is critical: “What happens to big trees – including how they deal with increasing climate threats and manage to disperse their seeds – is now mission-critical. Deforestation is a huge threat-multiplier and will kill them if we let it.”
The findings come as Brazil prepares to host COP30 later this year, where Amazon conservation will feature prominently in climate negotiations. The research underscores the vital role these forests play in absorbing carbon that would otherwise contribute to global warming.
While the Amazon’s trees are currently showing remarkable adaptation to rising CO2 levels, their continued health depends on protecting the forest from deforestation, fragmentation, and other human-caused disruptions. These giant trees, some hundreds of years old, represent irreplaceable carbon vaults that can help mitigate climate change – but only if they remain standing in healthy, connected forests.
