Trees in the Amazon Are Getting Bigger

A study out of the UK adds a new wrinkle to how climate change will affect the Amazon rainforest: It turns out that trees there are getting bigger. Researchers at the University of Cambridge and the RAINFOR Amazon Forest Inventory Network found that the average tree size has increased about 3.3% in diameter per decade over the last few decades, reports New Scientist. It appears to be related to a steady increase in atmospheric carbon dioxide levels in the same period, per a release at Phys.org.

"What we're following is some space in the forest and in that space the average tree size is bigger, meaning that the trees can pack more carbon in that space than they could in the past," says Adriane Esquivel-Muelbert at the University of Cambridge. The finding, published in Nature Plants, complicates debates about how forests will respond to climate change. Traditionally, scientists expected that larger trees would struggle to survive future conditions—like drought or storms—but so far, the opposite is happening.

"The structure of the Amazon forest is changing quite consistently across the whole basin," says researcher Rebecca Banbury Morgan of at the University of Bristol. "We have more bigger trees and fewer smaller trees, so the average size has shifted up towards those bigger trees." The researchers believe rising CO2 levels are essentially "fertilizing" tree growth, giving an edge to big trees that outcompete others for light and water. Still, the study leaves questions open. Peter Etchells of Durham University points out that this carbon-absorbing boon might not last as the climate keeps changing. Factors such as deforestation and shifting nutrient availability could eventually disrupt the trend, making the future of the Amazon as a carbon sink uncertain.