Emissões de metano decorrentes da expansão de áreas de soja no Cerrado brasileiro

Abstract

Mato Grosso (MT) is the state with the largest soybean production in Brazil, concentrated mainly in its areas in the Cerrado biome. Naturally, the Cerrado and its native vegetation are adapted to fire. Fires are one of the major vectors in the emission of greenhouse gases (GHG), with fires occurring in the Cerrado contributing significantly to methane (CH4) emissions. In this study, fire outbreaks, native vegetation areas and areas cultivated with soybean in the Cerrado of MT were quantified. Subsequently, emissions (CH4), Gross Primary Production (GPP) values and Standard Precipitation Index (SPI) classification were analyzed for the entire Cerrado of MT. For the classification of native vegetation areas the Random Forest classifier was used on satellite images obtained by the OLI/Landsat-8 sensor. For the detection of soybean areas, PCEI (Perpendicular Crop Enhancement Index) was applied on OLI/Landsat8 and Moderate Resolution Imaging Spectroradiometer (MODIS) images. Fire outbreak data were obtained through the Fire Information for Resource Management System platform. For CH4 methane data, data from the TROPOMI sensor attached to the Sentinel-5P satellite were used. GPP was obtained from the MODIS sensor by the MOD17A2H product. The results show that a difference was detected in the amount of native vegetation area between the years 2020 and 2021 of approximately one million hectares (Mha), where 12.5 Mha were detected in 2020 and 11.4 Mha in 2021. For soybean areas in the crop year 2020/2021 a cultivated area of 6.1 Mha was identified, increasing to 6.5 Mha in the crop year 2021/2022. The values recorded for methane emissions were 12.2 T mol/ m-2 for 2020 and 15.5 T mol/ m-2 for 2021, respectively. The GPP records were 11.61 g C m-2 d-1 for 2020 and 11.07 g C m-2 d-1 for 2021. SP1-12 classified the 2020 study area as extremely dry. The mean values for the agricultural expansion areas where there was deforestation by the burning method showed that higher CH4 concentrations per point occurred in 2021.