As we describe in research published this month (Brienen et al. Nature 519, 344–348), the biomass dynamics of apparently intact forests of the Amazon have been changing for decades with important consequences.
RAINFOR’s partners and other researchers have been taking a close-up look at Amazon forests since the 1980s, tracking the lives of hundreds of thousands of individual trees and thousands of species. This allows an unprecedented assessment of how Amazon forests have changed over the past three decades.
Researchers looked at trees right across the Amazon. RAINFOR, CC BY-NC-SA
Our analysis across 321 plots, 30 years, eight nations, and involving almost 500 people, first of all confirms earlier results. The Amazon forest has acted as a vast sponge for atmospheric carbon. That is, trees have been growing faster than they have been dying.
The difference – the “sink” – has helped to put a modest brake on the rate of climate change by taking up an additional two billion tonnes of carbon dioxide each year. This extra carbon has been going into ostensibly mature forests, ecosystems which according to classical ecology should be at a dynamic equilibrium and thus close to carbon-neutral.
However we also found a long, sustained increase in the rate of trees dying in ‘intact’ Amazon forests. Tree mortality rates increased by more than a third since the mid-1980s, while growth rates have stalled since the early 2000s. This had a significant impact on the Amazon’s capacity to take-up carbon.
Lars Hedin has also written a News and Views commentary on the paper.