Palm swamp peatlands in the Amazon Peru can usually absorb more carbon than they are released.
In their faces, the findings reported in the Journal Geophysical Research Book on June 30 may seem like a sign of trouble. But experts say there is more in the story.
Peatlands play an important role in the carbon cycle by absorbing carbon dioxide. In Peru, it covers approximately 22,000 square miles (56,000 square kilometers). This is less than 5% of the country’s total area. However, they store about 5 gigatons of carbon at the bottom. It is roughly equivalent to all carbon stored underground in Peruvian vegetation.
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It’s a similar photograph from around the world, and according to the International Union for Conservation of Nature, peatlands cover about 3% of the world’s land area, but they store at least 550 gigatons of carbon.
“Petatlands represent such a small area of land on Earth, but are extremely important as carbon inventory,” Jeffrey Wood, a biologist at the University of Missouri and lead author of the new study, told Live Science. “These systems have accumulated gigatons of carbon for tens of thousands of years.”
So what happened in Peru?
Important ecosystems
Wood and his colleagues have been studying the dominant variety of Amazon peat in the Quistococha Forest Reserve in Peru. Locally known as Aguariares, these marsh ecosystems are dominated by the Morihiepalms (Mauritiaflexhusa).
These major ecosystems develop in areas where flooding occurs every season, with the palms providing the locals with fruit called aguage, and fruit for macaws, monkeys, tapirs and agutis. These areas are densely vegetated shelters for many birds, reptiles and mammals.
Importantly, plants growing there absorb carbon dioxide (CO2) from the atmosphere through photosynthesis. However, because the area is flooded, dead leaves and other fallen material usually accumulate as peat in hypoxic environments. This traps carbon rather than completely decomposes and releases it into the atmosphere.
Wood and his colleagues discovered that peatlands had approached carbon neutrality in 2022 from strong carbon sinks in 2018 and 2019.
However, there were no clear signs of human influence in the ecosystem, Wood said. “The peatlands were not drained, and all the trees were not smashed or fell down by the storm,” he said. “It was also not a major drought year or a major heat wave.”
Instead, the researchers found that two factors were leading to change. First, the longer cloudless period and higher sun intensity limits the plant’s photosynthesis, which limits the growth and the amount of carbon dioxide absorbed.
Second, lower water levels left the top of the peat exposed. This means that the attenuators allow bacteria to utilize more oxygen, which decomposes faster and releases more carbon dioxide and methane gas than usual.
Lydia Cole, a conservation ecologist at St Andrews University in Scotland, told Live Science that, although he was not involved in the work, peat systems usually go through periods of greater carbon uptake and greater carbon release over a year, on average, usually net carbon absorption.
“There are areas that emit carbon and sinks across one landscape, and peatlands often have microtopography,” she explained. “So, on the mound, you might get more decomposition and emissions with carbon and dents, but it’s wet, so you get sequester.
At first, it seemed opposed to wood, that more sunlight means less photosynthesis. But that could happen because Quistococha’s rainforest is generally covered with thick clouds, he said.
“Plants are exposed to much more light than they can handle,” Wood told Live Science. If there is too much light and heat, the plant closes pores, called stomata, on top of the leaves.
Therefore, photosynthesis often drops at midday in rainforests, with timber and his colleagues seeing its standard pattern in Peru. However, what changed was usually in very productive mornings and afternoons, with photosynthesis below normal levels at higher light intensity.
One major question is whether the peatlands will return to the carbon sink, maintain carbon neutrality, or proceed to release enormous amounts of stored carbon.
Wood is optimistic that peatlands will regain future sink capacity.
Chris Evans, a biogeochemist from Welsh peatlands at the UK Centre for Ecology and Hydrologies, also advised from drawing conclusions based on a year. “We would expect to see a variance between net sinks and neutrals depending on weather conditions.[ly] Evans told Live Science.
Human shock
However, the changes observed by wood and his colleagues occurred when there was no obvious human interference, but that does not mean that humans have no effect on the sink or will not in the future.
“One ecosystem does not function as an island,” Cole said. The larger area created after deforestation includes grassland and settlement areas. This could have changed local weather patterns, she said, which provided long-term climate change.
It is unclear how climate change will affect tropical peatlands in Peru and elsewhere in the Amazon, but Wood said the impact on cloud cover and water table changes is likely to affect the strength of these carbon sinks.
Jean Ometo, director of the Earth Systems Science Center at the Brazilian National Space Institute, was not involved in the work, but told Live Science that water table variations are generally a major issue for the Amazon.
“In the Amazon in Brazil, we are facing extremes of extreme flooding and drought,” he said. “Droughts are frequent, so water tables can be a long-term process. With climate change, it can be a permanent process, which is a major problem.”
The findings should be taken seriously, but should be put into view, Cole said. “We should not cry wolves about this,” she said. “But we also need to be really serious about how we can protect the peatlands we are healthy and how we can re-melt those peatlands that still have the ability to isolate carbon in the future.”
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