Sustainability in Natural Grassland in the Brazilian Pampa Biome: Livestock Production with CO 2 Absorption

The Brazilian Pampa biome has natural pastures that have been used for centuries for cattle grazing. This is considered a sustainable system because it combines the conservation of natural vegetation and high-quality meat production, protecting the biome from commercial agriculture’s advances. However, whether it is a source or a sink of carbon dioxide (CO 2 ) has yet to be evaluated. Hence, this study aimed to quantify the net ecosystem exchange (NEE) of the CO 2 of a natural pasture of the Pampa biome used for livestock production. The experimental area is located in a subtropical region of southern Brazil, where eddy covariance (EC) measurements were conducted from 2015 to 2021 in a rotational cattle grazing system. The seven months of the warm season (September to March) were characterized as CO 2 absorbers, while the five months of the cold season (April to August) were CO 2 emitters. Throughout the six years and with complete data, the ecosystem was an absorber of atmospheric CO 2 , with an average value of −207.6 g C m −2 year −1 . However, the significant interannual variability in NEE was observed, with cumulative values ranging from −82.0 to −385.3 g C m −2 year −1 . The results suggest the coupling of climatic conditions to pasture management can be the factor that modulated the NEE interannual variability. The cattle raising system on the natural pastures of the Pampa absorbs CO 2 , which is further evidence of its sustainability and need for conservation.