The wetlands and veredas of Brazil's Cerrado savanna-like biome can store up to 1,200 tons of carbon per hectare. This is about six times the biomass stock of typical Amazonian forests. Dating indicates that this carbon has, on average, been in place for 11,000 years and, in some cases, as long as 20,000 years. This is the result of a slow accumulation process favored by the lack of oxygen in water-saturated soils.
The findings come from a study published in the scientific journal New Phytologist and led by researchers from the Institute of Biology at the State University of Campinas (IB-UNICAMP) in the state of São Paulo, Brazil.
Since these groundwater-dependent wetlands are poorly studied, the scientists conducted an initial mapping using remote sensing data combined with machine learning. This analysis indicates that the wetlands may cover 167,000 square kilometers (km²) in the Cerrado. This represents a region at least six times larger than previously thought: about 8% of the biome and 2% of Brazil's territory.
The Cerrado, the second-largest biome in South America, is the world's most biodiverse savanna. It is known as the "cradle of waters" because it contributes two-thirds of the water supply to major river basins, especially in the country's South and Southeast regions. It also contains seeps or "water eyes" – natural outcrops of the water table – including diffuse ones , which are protected by the Forest Code (Law No. 12,651/2012) and classified as Permanent Preservation Areas (APPs).
Immortalized in the novel Grande Sertão: Veredas – which celebrates its 70th anniversary in 2026 – by writer João Guimarães Rosa (1908–1967), veredas are a type of peatland, which are flooded and marshy ecosystems. In addition to storing carbon, they are significant sources of methane (CH₄), especially in permanently flooded areas where higher temperatures increase emissions.
Though barely visible and often overlooked, these formations play a crucial ecological role as sources for rivers and watersheds. However, according to the researchers, these ecosystems are highly vulnerable to changes in the water regime caused by agricultural expansion, deforestation, wetland drainage, small dam construction, and intensive water use for irrigation.
Even when preserved in fragments, changes in the surrounding environment can lower the water table and transform these soils into sources of carbon emissions.
"If we cut down a tree that's been in the forest for 300 years, we lose a large carbon stock and important ecosystem functions that are difficult to fully restore. But with the forest restoration process, it's possible to get close to that in 30 or 40 years. In other words, you can plant trees and witness this process during your lifetime. However, we won't recover the carbon in the soil of a Cerrado wetland within our lifetime, since it was stored over tens of thousands of years," explains Larissa da Silveira Verona , the first author of the article and a biologist, to Agência FAPESP.
The study is partly based on her master's thesis, which was supervised by Professor Rafael Silva Oliveira and awarded the best thesis prize in the Graduate Program in Plant Biology at IB-UNICAMP in 2024.
Verona is currently working at the Cary Institute of Ecosystem Studies in the United States with Amy Zanne, another author of the article. She received a scholarship from FAPESP , which also supported the study through a Research Grant awarded to Oliveira.
"The Cerrado was chosen as Brazil's primary agricultural frontier geared toward large-scale commodity production. Situated between two forest formations, the Amazon and the Atlantic Forest, the biome faces intense pressure for conversion and, unlike those forests, it isn't recognized as national heritage in the Constitution, and it has a legal requirement of only 20% for preservation areas. Unfortunately, there's a perception that maintaining APPs along rivers is enough to conserve the biome's ecosystem functions. We're finding that's not the case. To maintain the Cerrado's hydrological processes, we must understand the connectivity of the landscape. It isn't enough to preserve small fragments while the rest of the territory is converted," adds Oliveira, a co-author of the article.
Despite a downward trend, deforestation rates in the biome remain high. From August 2025 to January of this year, 1,905 km² of the Cerrado were under deforestation alert, compared to 2,025 km² in the previous period (a 6% decrease), according to data from the Real-Time Deforestation Detection System (DETER) of the National Institute for Space Research (INPE).
A MapBiomas survey , conducted by a collaborative network of non-governmental organizations, universities, and technology startups that map land cover and land use in Brazil, showed that 47% of the Cerrado is occupied by human-used areas (2024 data). Of this, 24% is used for pasture and 13% for agriculture, most of which is dedicated to soybean cultivation. Regarding water surface area, the document shows that 2024 had the largest area since 1985, but 60% of it is used for human activities, much of which is for hydroelectric power.
Fieldwork
The research is pioneering in its use of deep soil samples (up to four meters deep) to quantify carbon in these environments. Soil samples were collected from veredas and wet fields at seven locations in Chapada dos Veadeiros National Park in Goiás state in 2023.
"Collecting these samples involved exploring some regions. There were places where the vegetation reached my shoulder height, and, since it's flooded, your feet often sink into the mud. Our soil is denser than others, so it was physically exhausting – sometimes requiring five or six people to operate the equipment – but the results are very rewarding," says Verona.
The group used a LI-COR Trace Gas Analyzer connected to PVC rings installed in the ground to measure carbon dioxide and methane.
To perform carbon dating, the UNICAMP researchers collaborated with scientists from the Max Planck Institute in Germany. Paulo Negri Bernardino from UNICAMP and Guilherme Gerhardt Mazzochini from the Rio de Janeiro Botanical Garden contributed to mapping the areas using remote sensing.
The study also indicated, through spectroscopy, low carbon stability compared to other tropical peatlands. About 70% of annual CO₂ and CH₄ emissions occurred during the dry season. Since most of the vegetation in these wetlands is grass, which decomposes easily, stored carbon can be released as emissions when the soil dries out. This process may be exacerbated by climate change and increased hot, dry seasons.
In the article, the researchers emphasize the importance of expanding the protection of wetlands and raising awareness about these zones, which are fed by groundwater. They also emphasize the importance of expanding mapping efforts and conducting more in-depth studies to better understand these ecosystems.
In this regard, Verona says she is continuing her research on seasonal wetlands in order to better understand the carbon dynamics. Meanwhile, Oliveira is deepening his analysis of the hydrological system to better understand how these ecosystems function and how to restore them.
"If we lose peatlands or veredas, it'll take thousands of years to restore stored carbon levels, not to mention the losses in other ecosystem services. Preservation is the way forward, but we must continue trying to better understand the processes," the professor notes.
Another article led by Oliveira and published last year highlighted that despite their importance for water security and legal protection, the Cerrado's wetlands, including the "water eyes," continue to be systematically neglected by public policies, environmental consultants, rural landowners, and regulatory agencies (read more at agencia.fapesp.br/55808 ).
About São Paulo Research Foundation (FAPESP)
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