The ability of the world’s tropical forests to remove carbon from the atmosphere is decreasing, according to a study tracking 300,000 trees over 30 years.
Published in Nature, the global scientific collaboration reveals that a feared switch of the world’s undisturbed tropical forests from a carbon sink to a carbon source has begun.
Intact tropical forests are well-known as a crucial global carbon sink, slowing climate change by removing carbon from the atmosphere and storing it in trees, a process known as carbon sequestration.
However, the new analysis of tree growth and death in 565 undisturbed tropical forests across Africa and the Amazon has found that the overall uptake of carbon into Earth’s intact tropical forests peaked in the 1990s.
By the 2010s, on average, the ability of a tropical forest to absorb carbon had dropped by one-third. The switch is largely driven by carbon losses from trees dying and goes against the typical predictions of climate models.
The study involved almost 100 institutions – led by the University of Leeds and including the University of Plymouth – and provides the first large-scale evidence that carbon uptake by the world’s tropical forests has already started a worrying downward trend.
Dr Sophie Fauset, Lecturer in Environmental Science in Plymouth’s School of Geography, Earth and Environmental Sciences, provided data from 15 forest plots in Ghana, measured during her PhD.
This required nine months of fieldwork with the help of collaborators and field technicians in the country, with her data making up 6% of the new African dataset used in the paper.
She also contributed data to a previous study of forests in the Amazon, which has also been used to draw the conclusions in the current paper.
Dr Fauset said: