Study points to a billion-dollar carbon deficit in Brazilian soils.

A groundbreaking study indicates that the conversion of native vegetation into agricultural areas across Brazil's six biomes has resulted in a carbon deficit of 1,4 billion tons in the 0-30 centimeter layer of soil. This loss is equivalent to an emission of 5,2 billion tons of CO2 equivalent (carbon dioxide equivalent). The data is based on research that evaluated over 370 studies and identifies areas with the greatest potential for soil recarbonization, in addition to providing input for public policies and private initiatives aimed at adopting sustainable agricultural practices.

The research, published in the journal Nature Communications, was developed by scientists from the Luiz de Queiroz Higher School of Agriculture (Esalq/USP), the Center for Carbon Studies in Tropical Agriculture (CCarbon/USP), the State University of Ponta Grossa (UEPG), and Embrapa.

This is the first time that carbon stocks in Brazil have been calculated before anthropogenic interventions, and the deficit caused by the conversion of native vegetation areas into crops and pastures has been measured. 

This article is the result of scientific collaboration.

The article "Soil carbon debt from land use change in Brazil" was authored by: João Marcos Villela, scholarship recipient at Esalq/USP; Júnior Damian, scholarship recipient at Embrapa; Daniel Potma and Luis Gustavo Barioni, both researchers at Embrapa Agricultura Digital (SP); and Maurício Cherubin and Carlos Eduardo Cerri, from Esalq/USP and CCarbon.

This work was funded by the São Paulo Research Foundation (FAPESP), the National Council for Scientific and Technological Development (CNPq), Bayer, and Shell Brazil.

The study utilized an extensive database with 4.290 soil samples, collected at different depths (0-10 cm, 0-20 cm, 0-30 cm, and 0-100 cm), from areas of native vegetation and agricultural land use throughout the country. The differences between the values ​​of organic carbon stock in the soil served as the basis for the calculation and allowed for an understanding of carbon loss in six biomes, five soil types, and different levels of intensification of agricultural management.

“While quantifying the problem, the research points to opportunities for increasing carbon emissions through changes in agricultural practices, public policy initiatives, or private actions,” explains Luis Gustavo Barioni, a researcher at Embrapa.

According to João Marcos Villela, first author of the article and scholarship recipient at Esalq/USP, the study establishes a baseline on carbon loss in Brazil and serves as a reference for other research on this topic.

"Since the data comes from different studies, there is no methodological uniformity. However, we didn't have information with this breadth before."

"This work serves as a benchmark for future actions," says Villela, highlighting that CCarbon has approved a project to expand data collection throughout Brazil in a standardized way, enabling the refinement of the numbers.

The database is the result of a systematization effort based on more than 370 studies. “It was a very extensive evaluation, in which we used several criteria; we broke it down, for example, by geographic information, soil types, biome, and management practices. We collected this data and, from that, we sought to do something that made sense for our country, in terms of the carbon market and climate change,” explains Júnior Damian, a fellow at Embrapa and one of those responsible for the database. The database published in the article is in open format and available for other studies.

Climate influences carbon loss.

In addition to measuring the carbon loss caused by land-use changes, the researchers wanted to know what alternatives exist to increase carbon stocks, potentially returning to the initial stage, or even surpassing it.

Data analysis confirmed that climate is an important factor in the balance of organic carbon loss and storage in the soil. Colder and more humid locations, such as the Pampa and Atlantic Forest biomes, showed higher carbon stocks compared to tropical biomes like the Cerrado, Pantanal, Caatinga, and Amazon.

Similarly, changes in land use, with the introduction of agricultural practices, caused greater carbon loss in locations with higher initial carbon stocks.

The role of sustainable agricultural practices

The study also compared soil carbon stocks in different production systems, such as monoculture, crop rotation, and integrated farming systems like crop-livestock integration (CLI). According to the data, carbon losses decrease as agricultural systems intensify and diversify.

The conversion of native vegetation to monoculture resulted in an average loss of 22% in organic matter, while in integrated agricultural systems the loss was 8,6%. The no-till system also proved less susceptible to carbon loss than conventional planting. In this system, the reduction was 11,4%, while in conventional cultivation it was 21,4%. This results in a 47% difference between the two sowing techniques. 

Policy targeting for recarbonization

Quantifying lost carbon makes it possible to theorize the country's carbon stock potential and guide the identification of regions where it is easier to increase organic carbon in the soil. According to researchers, about 72% of the recarbonization potential is in the Cerrado and Atlantic Forest biomes. The Cerrado would contribute 0,53 billion tons of C, and the Atlantic Forest 0,48 billion tons of C.

Focusing on regions with the greatest potential for increasing carbon stocks will allow Brazil to meet the target set in its Nationally Determined Contributions (NDCs) under the Paris Agreement. Despite its limitations, the study offers a good quantitative benchmark, allowing us to state that by recarbonizing one-third of the estimated potential, the target for reducing Brazilian emissions by between 59-67% will be achieved by 2035.

“Understanding the differences in this diversity of climates, biomes, and production systems, both in terms of losses and gains, helps to direct more adapted solutions. We can direct the agricultural system with greater efficiency in carbon input in each region,” highlights João Marcos Villela.

carbon market

In addition to supporting public policies for recarbonization, the research provides important information about the potential of the carbon market in Brazil. Daniel Potma, currently a researcher at Embrapa Agricultura Digital, and affiliated with the State University of Ponta Grossa at the time of the study, states that defining the carbon deficit allows us to estimate the size that this market can reach.

“Knowing the size of the ‘pot,’ 1,4 billion tons of carbon, it’s possible to understand its value in terms of resources, which could be an incentive to attract investment in the decarbonization economy,” he points out.

International support

The publication of this study in a high-impact journal such as Nature Communications contributes to the recognition of Brazilian science and data on greenhouse gas emissions in national agriculture.

Researcher Luis Gustavo Barioni emphasizes that climate negotiations and countries' commitments are based on scientific information recognized by the international community. Therefore, research like this strengthens Brazilian diplomacy.

"Reliable information obtained nationally is fundamental to supporting and lending credibility to our policies and other initiatives at a global level," adds Barioni.

Understanding units of measurement

One billion tons is the same as 1 pg (petagram) or 10¹⁵ grams.

CO2 eq – Carbon dioxide equivalent. It is a measure that represents the warming potential of greenhouse gases when converted to the same base, carbon dioxide (CO2). Methane (CH4), for example, has a warming potential 28 times greater than that of CO2. The warming potential of nitrous oxide (N2O) is 273 times greater. Therefore, one ton of methane is equal to 28 tons of CO2 eq and one ton of nitrous oxide is equal to 273 tons of CO2 eq.