Livestock intensification and environmental sustainability: An analysis based on pasture management scenarios in the brazilian savanna.

ABSTRACT

Brazil's major beef production occurs in the Cerrado, predominantly as extensive pastures that covers ∼50 Mha of the biome, of which approximately 2/3 show signs of degradation. Pasture recovery is now a key environmental policy, as it improves land use efficiency and soil carbon sequestration. However, as intensification leads to higher cattle stocking rates and external inputs (fertilizers, liming, etc.), the impact of improved pastures on greenhouse gas mitigation is still debatable. This study focused on the Cerrado biome and aimed to (i) quantify soil carbon stock changes under different scenarios of management and recovery of degraded pastures. In addition, (ii) the potential for capturing carbon in the soil to mitigate emissions of greenhouse gases (GHG) by the intensification of pastures was evaluated. Soil C stock changes (0-20 cm) were assessed using the Century model version 4.5, which had been previously validated for the region. Model parameters were adjusted for three pastures classes (degraded, intermediately degraded, and not degraded) within a time-series (1985-2020) of land use maps for the Cerrado, serving as baselines. Scenarios of pasture intensification were modeled against these baselines, and an analysis was carried out on the estimated changes in soil C stock and greenhouse gas balance. Before the intensification scenario (year 2020), the total carbon stock was estimated to be ∼1830 Mt for the whole pasture area, whose spatial distribution corresponded to edaphoclimatic contrasts and pasture conditions. The highest soil organic carbon stocks were observed in the non-degraded pastures. With the increase in carrying capacity, beef production is estimated to potentially increase by 1/3 due to the recovery of degraded areas through intensive management. This increase would be sufficient to meet the projected ∼12% increase in Brazil's livestock production by the end of the decade if all pasture areas are restored, which is much possibly an unrealistic scenario as not all degraded areas are suitable for crops or can successfully improve pasture yield. In addition, the increase in soil C stocks was only sufficient to compensate for 27% and 42% of the GHG emissions resulting from intensification in areas with intermediate and severe degradation, respectively. Therefore, to strike a balance between economic considerations and environmental impact, additional strategies are needed to reduce GHG emissions and/or enhance C sinks, such as increasing tree density on farms. From this perspective, implementing livestock intensification at the landscape scale can promote C stocks and the diversity of ecosystem services, opening the possibility of ecosystem restoration.