Brazil: New soil carbon stock maps will support public sustainability policies

The new organic carbon stock maps of Brazilian soils were launched as part of the National Soil Survey and Interpretation Program in Brazil (PronaSolos), on Wednesday, October 27. 

The material is an essential tool to support public policies related to climate change and reduce the emission of Greenhouse Gases (GHGs), with efficient management of natural resources. 

Knowing the distribution of carbon in soils in Brazil, in different regions, states, municipalities, biomes and agricultural borders is essential for defining strategies and directing public policies, especially those whose themes are linked to the decarbonization of agriculture and the recarbonization of the soil, such as the ABC+ Plan and the Águas do Agro program, both on Mapa.

Through this work, developed by researchers from Embrapa Solos, in partnership with Embrapa Digital Agriculture, it will be possible to identify the potential areas in Brazil for the practice of a green economy, which will positively impact the fulfillment of Brazilian commitments for the mitigation of climate change.

Deputy Secretary of Innovation, Rural Development and Irrigation of the Ministry of Agriculture and representative of the coordination of the Strategic Committee of PronaSolos, Cleber Soares, highlighted the importance of soils for agriculture. “The greatest asset of the rural producer is called soil for which he is responsible. Through our soils we produce food, fiber, energy and other functions derived from agriculture. At this moment, it is opportune to present and make available these maps because it is the moment when the world discusses and calls, more and more, for a sustainability agenda. And soils are one of nature's biggest carbon sinks. So, we need to know more about our soils.”

The new maps provide unprecedented information in the country by providing a detailed portrait of the organic carbon stored in the Brazilian soil down to a depth of two meters, at a spatial resolution of 90 meters (equivalent scale between 1:250,000 and 1:100,000). In addition, carbon information up to one meter in depth is broken into five layers: 0-5 centimeters (cm); 5-15 cm; 15-30 cm; 30-60 cm; and 60-100 cm deep. This detail shows the evolution of the survey concerning previous maps, released in 2017, whose analysis was conducted at a depth of 0-30 cm, at a resolution of 1 kilometer.

Among the variables used to generate the maps are relief, such as flat valley floor index, elevation and terrain roughness index, and climate variables, such as average annual precipitation, the temperature in the coldest quarter and solar radiation.

The new maps are available for consultation and download on the PronaSolos Data Portal (SigWeb). The virtual environment brings together, in a geographic information system, maps and soil data produced by the Geological Service of Brazil (CPRM), the Brazilian Agricultural Research Corporation (Embrapa) and the Brazilian Institute of Geography and Statistics (IBGE). It allows for cross-referencing between some of these products based on the selections requested by the user. 

Presentation at COP26

The new maps will join other Brazilian initiatives to be presented at the United Nations Conference on Climate Change 2021 (COP26), in Glasgow, Scotland, from October 31 to November 12. “Brazil is positioned in the forefront and the frontier of knowledge and innovation in sustainability. On the eve of COP 26, in addition to having announced the ABC+ plan, a decarbonization program for our agriculture, today, together with other partners, we are presenting the new soil carbon maps. We also present this week, in partnership with the Ministries of Economy and Environment, the Green Growth Program. Agriculture is playing its role of contributing not only to the decarbonization of its activities but mainly with a climate security agenda.”

According to the General Head of Embrapa Solos, Maria de Lourdes Brefin, soils play a decisive role in climate change. “These maps have a lot to do with this baseline, with knowledge of Brazilian soils in terms of carbon. Especially for this crucial moment before COP 26 and where agricultural soils should be part of the climate change mitigation solution.”

According to Brefin, soils function both as a source and sink of carbon. “They are a source of CO² when they are poorly handled and when they transmit Greenhouse Gases into the atmosphere. And its most important role is as a sink, to sequester this carbon from the atmosphere and stabilize it in the soil's organic matter,” Brefin said.

Soil is one of the five carbon reservoirs of the terrestrial ecosystem, with biota, oceans, atmosphere and geological formations. “If you add biota and atmosphere together, the soil has more carbon than these two put together. In fact, 2/3 of the entire carbon pool is in the ground. So, it is up to us researchers, farmers and decision-makers to generate actions and public policies that can maintain and increase the organic matter in the soil and keep this carbon in the soil,” Brefin emphasized.

Distribution

The spatial distribution of carbon stock in the soil can vary according to the type of soil, climate, the geological material that formed the soil and, especially, depending on the use and management of the soil. The greater the organic matter content of a soil, the greater its carbon sequestration power.

The maps were generated using Digital Soil Mapping methodology and high-performance computing from data organized by the Embrapa Solos project team titled “National Soil Attribute Maps: Contribution to PronaSolos, GlobalSoilMap and the World Alliance for Soil”. 

According to the maps presented by Gustavo Vasques, Head of Research and Development at Embrapa Solos, the Amazon region and Southern Brazil have a greater amount of carbon stock. “There is a large pocket in the southern mountains, where there are soils formed with richer material, formed from basalt, and soils formed at altitude, in flat and high places. This environment favors the accumulation of carbon because degradation is slower due to the cold. At the same time, it has a good production of vegetable mass. In the Amazon, plant mass production and primary productivity are very high. So, despite having a hot climate and lots of rain, which promotes degradation, the cycling of nutrients is huge, which allows carbon to accumulate.”

In contrast, the carbon concentration in the Pantanal and Caatinga soils is lower. “The Pantanal has more sandy soils. So, despite having a quantity of flooded soils, these soils accumulate very little because they do not have clayey material where this carbon and organic matter is retained. So, she is lost in the rain. The Caatinga is another example where you have low stocks, because with little rain, you produce little vegetation. As you do not have vegetation providing carbon and organic matter, these soils, over thousands of years, accumulated little carbon,” Vasques said.

By comparing the 2017 and 2021 carbon stock maps, at 0-30 cm, the head of research at Embrapa Solos assessed that Brazil is on the right path. “I am struck by the fact that the total stock, of about 36 billion tons of carbon, is quite similar between 1 km and 90 m. This brings us to an awareness that we are hitting the mark, at least globally. This stock is 5% of the global carbon stock of 0-30 cm and Brazil is the outstanding tropical country, due to its size, among the countries in the world, contributing to the global stock.”

Soils from Brazil

PronaSolos is the largest Brazilian soil investigation program, which consolidates data integration and collaborates with the advancement of knowledge of soils in the country. Its creation began in 2015, when a working group was set up coordinated by Embrapa Solos and composed of researchers from other units of Embrapa, Mapa, IBGE, the Brazilian Society of Soil Science (SBCS), the Research Company of Mineral Resources (CPRM), the Federal Rural University of Rio de Janeiro (UFRRJ), the Federal University of Piauí (UFPI), the State University of Santa Catarina (UDESC) and the Federal University of Lavras (UFLA), which formulated the base document for the creation of the program.

PronaSolos was made official with the signing of Decree No. 9,414, of June 19, 2018, and its governance structure, which has Strategic and Executive committees, was established by Decree No. 10, 269, of March 6, 2020.

For 30 years, the program's mission has been to foster knowledge about Brazilian soils, based on the mapping of the entire national territory, involving partner institutions dedicated to research, documentation, training of professionals, systematization of information on the sciences of the soil, increase in the realization of inventories and interpretation of Brazilian soil data. The goal is to map the country's 1.3 million km² soils in the first ten years and another 6.9 million km² by 2048.

Currently, PronaSolos cooperates with more than 40 public and private institutions that have joined in a continental challenge for better soil management in Brazil. Based on the detailed knowledge about the soils made available on a single technological platform, the initiative seeks to increase the usability of data and information, improving the application of knowledge.

The information collected by PronaSolos will contribute to boosting agricultural productivity, optimizing urban expansion, preventing risks and catastrophes, valuing land and granting agricultural credit. Especially for agriculture, the program results will allow us to know where the most suitable areas are for the sustainable growth of agricultural and livestock production in the national territory.

The original Portuguese version of this article was released on GRUPO CULTIVAR.