Brazil’s Cerrado Wetlands: Hidden Carbon Stores Rival Amazon Rainforest

Brazil’s Cerrado savanna, a vast tropical ecosystem covering roughly 26% of the country, is increasingly recognized not just for its incredible biodiversity – home to over 12,000 plant species and a wealth of animal life – but for its surprisingly potent capacity to store carbon. New research reveals that the wetlands within the Cerrado sequester carbon at a rate six times greater than the Amazon rainforest’s vegetation, highlighting the critical, and previously underestimated, role this region plays in global climate regulation.

The Cerrado similarly functions as a vital water source, feeding the headwaters of two-thirds of Brazil’s major waterways, including the Amazon River. The Amazon River’s health is inextricably linked to the Cerrado’s, making the preservation of this savanna essential for regional water security.

Unearthing the Cerrado’s Carbon Storage Potential

For years, the Cerrado’s carbon storage capabilities were overlooked. Previous studies indicated high carbon levels in the region’s soils, but sampling was often limited to surface levels (within a meter) and focused on higher elevation areas. The unique characteristic of the Cerrado – its groundwater-fed wetlands – weren’t easily detectable from above, leading to an underestimation of their true potential. As Amy Zanne, an ecologist at the Cary Institute of Ecosystem Studies, explains, “We have very little information from field science” when it comes to understanding carbon cycles in tropical wetlands.

The recent study, published in New Phytologist, employed a more comprehensive approach. Researchers extracted soil cores several meters deep from seven sites across the Cerrado and analyzed the carbon content at various layers. This detailed analysis revealed an average carbon density of 1,200 metric tons of carbon per hectare – a surprisingly high figure, even when compared to soils typically considered carbon-rich, like peat.

Whereas the soils studied didn’t quite meet the classical definition of peat (requiring around 30% organic matter, compared to the Cerrado’s average of 16%), their sheer density resulted in significantly higher carbon storage. Julie Loisel, a peatland ecologist at the University of Nevada, Reno, who was not involved in the study, noted that the data richness is a significant contribution, “filling a really big data gap” in our understanding of tropical carbon cycles.

Age of the Carbon: A Millennial Timescale

Further analysis using radiocarbon dating revealed that the carbon stored in the Cerrado is, on average, over 11,000 years old, with some samples dating back as far as 20,000 years. This age underscores the importance of protecting these ecosystems; carbon accumulated over millennia cannot be easily replaced if lost. As Zanne emphasizes, “If we lose the carbon in the Cerrado that has accumulated for millennia, we can’t put it back so easily.”

Vulnerability and Threats to the Cerrado

Despite its immense carbon storage capacity, the Cerrado is facing increasing threats from land apply changes, agricultural expansion, and the accelerating effects of climate change. The study also found that approximately 70% of greenhouse gas emissions from the Cerrado’s wetlands occur during the dry season, raising concerns that prolonged droughts could lead to a rapid release of stored carbon.

Currently, Brazilian law offers some protection to wetland areas, but these protections often fail to address the critical need to safeguard the water sources that sustain them. Larissa Verona, lead author of the study and an ecologist at the Universidade Estadual de Campinas in Brazil, points out that protecting only the wetlands themselves, without addressing the broader hydrological system, is insufficient. “If you protect only the wetlands per se and don’t protect the water in the landscape…we will lose the hydraulic system.”

The Cerrado is often described as a “sacrifice biome,” absorbing land-use pressures that might otherwise impact the better-protected Amazon rainforest. Though, Verona argues this is counterproductive, as the Cerrado’s water resources are essential for maintaining the Amazon’s health.

Implications for Carbon Accounting and Policy

A significant finding of the study is that the Cerrado’s substantial carbon stores have not been adequately incorporated into Brazil’s national carbon accounting. Without detailed scientific data, it’s difficult to accurately assess the carbon emissions resulting from wetland degradation. Rafael Oliveira, an ecologist at Universidade Estadual de Campinas, highlights this issue: “Without detailed scientific information, ‘we have no clue what the emissions are’ when these wetlands are degraded. ‘What are we losing in terms of carbon?’”

The research team used remote sensing data, land use information, and machine learning to estimate that the Cerrado’s wetlands cover approximately 16.7 million hectares, representing about 8% of the total area of the savanna. This estimate, combined with the carbon density measurements, provides a more accurate picture of the Cerrado’s overall carbon storage potential.

What’s Next: Strengthening Protections and Filling Data Gaps

The study underscores the urgent need for stronger protections for the Cerrado’s wetlands. This includes implementing policies that recognize the interconnectedness of groundwater and wetlands, as well as enacting more effective water usage regulations. Addressing the issue requires a shift in perspective, recognizing the Cerrado not as a disposable landscape, but as a critical component of both regional and global climate stability.

Further research is needed to fully understand the complex carbon dynamics within the Cerrado and to monitor the impacts of climate change and land use practices. Continued investment in field science, alongside remote sensing technologies, will be crucial for refining carbon accounting and informing effective conservation strategies. As Oliveira states, “They remain invisible in policy in Brazil, and even for the global scientific community. They really deserve urgent, stronger protection and recognition at the global level.”

This article was originally published on Eos.org. Read the original article.