Peatlands cover just a fraction of Earth’s surface, but store huge amounts of carbon. In the Peruvian Amazon, one of these swamps has switched to carbon neutral.

A palm swamp peatland in the Peruvian Amazon that normally absorbs more carbon than it releases each year has switched to being carbon neutral, even with no major disturbance by local people.

On their face, the findings, reported June 30 in the journal Geophysical Research Letters, may seem like a sign of trouble. However, experts say there’s more to the story.

Peatlands play a crucial role in the carbon cycle by absorbing carbon dioxide. In Peru, they cover some 22,000 square miles (56,000 square kilometers) — less than 5% of the country’s total area. Yet they store about 5 gigatons of carbon belowground — roughly equivalent to all of the carbon stored aboveground in vegetation in Peru.

It’s a similar picture globally, where, according to the International Union for Conservation of Nature, peatlands cover about 3% of the world’s land area but store at least 550 gigatons of carbon — more than twice the carbon stored in all the world’s forests.

“Peatlands represent such a small land area on Earth, but they are massively important as stocks of carbon,” Jeffrey Wood, a biometeorologist at the University of Missouri and lead author of the new study, told Live Science. “These systems have accumulated gigatons of carbon over tens of thousands of years.”

So what has happened in Peru?

Key ecosystems

Wood and his colleagues have been studying the dominant kind of Amazonian peatland in Peru’s Quistococha Forest Reserve. These swampy ecosystems, known locally as aguajales, are dominated by moriche palms (Mauritia flexuosa).

These key ecosystems develop in areas that flood seasonally, with the palms providing a fruit called aguaje for locals, as well as for macaws, monkeys, tapirs and agoutis. These areas are densely vegetated havens for many birds, reptiles and mammals.

Crucially, the plants that grow there absorb carbon dioxide (CO2) from the atmosphere through photosynthesis. But because the area is waterlogged, their dead leaves and other fallen matter usually accumulate as peat in the low-oxygen environment, which traps carbon instead of fully decomposing and releasing it back into the atmosphere.

Wood and his colleagues found that the peatland switched from being a strong carbon sink in 2018 and 2019 to being about carbon neutral in 2022.

Yet there were no obvious signs of human effects on the ecosystem, Wood said. “The peatland hadn’t been drained and the trees hadn’t all been cut down or taken down by a storm,” he said. “It also wasn’t a major drought year or a major heat wave.”

**Instead, the researchers found that two factors led to the change. The first is that prolonged cloudless periods and higher sun intensities limited the photosynthesis of the plants, thus restricting their growth and how much carbon dioxide they absorbed.

The second was that lower water levels left more of the top of the peat exposed. This meant more oxygen was available to bacteria in the decaying matter, which decomposed faster, releasing more carbon dioxide and methane gases than usual.**