New research reveals that Brazil's cerrado savanna, often overshadowed by the Amazon rainforest, holds six times more carbon per hectare in its underground peat than the Amazon's biomass. This biodiverse ecosystem faces threats from climate change and expanding agribusiness. Protecting its wetlands could significantly aid global efforts to curb planet-warming gases.
The cerrado, Brazil's second-largest biome after the Amazon, is a vast savanna known for its swaying grasses and scattered trees, making it the world's most biodiverse savanna. Beneath the surface, its wetlands harbor peat—concentrated carbon formed in waterlogged, oxygen-poor conditions that prevent decay of dead vegetation. Deposits in the cerrado can date back 20,000 years, sustained by groundwater that keeps the soil moist even during the four-to-five-month dry season.
Ecologist Larissa Verona, lead author of a recent study conducted while at the State University of Campinas and now at the Cary Institute of Ecosystem Studies, analyzed soil cores up to 13 feet deep. The findings show these peatlands store more than 1,300 tons of carbon per hectare. "When you degrade it—one hectare of Amazon and one hectare of wetland in the cerrado—we are losing six times more carbon," Verona said.
The cerrado's groundwater system not only preserves the peat but also feeds eight of Brazil's 12 major waterways, including some flowing to the Amazon. In a single 3-foot-by-3-foot plot, researchers identified 50 plant species, highlighting the area's rich, if subtle, biodiversity. Co-author Amy Zanne, an ecologist at the Cary Institute, noted, "They’re tiny, so you don’t notice them, like a big Amazon tree, but they’re hugely rich in diversity."
However, rising temperatures and a lengthening dry season are drying out the peat, making it vulnerable to wildfires. These fires, fueled by desiccating peat, smolder longer than typical grass fires, releasing greenhouse gases and harmful particulate matter. Agribusiness, particularly soy farming, exacerbates the issue by tapping groundwater needed to maintain wetland conditions. The cerrado receives less legal protection than the Amazon, allowing such encroachment.
"If you only protect the place, but not protect the water, we are not protecting the carbon," Verona emphasized. Unlike the rapid growth of Amazon trees, peat accumulation occurs over millennia. "If you lose this, to accumulate this again will demand thousands of years," she added. While ecosystems can be restored, lost carbon cannot, underscoring the need to safeguard both land and water in the cerrado.