Greenhouse gas balance and carbon footprint of pasture-based beef cattle production systems in the tropical region (Atlantic Forest biome)

The production of beef cattle in the Atlantic Forest biome mostly takes place in pastoral production systems. There are millions of hectares covered with pastures in this biome, including degraded pasture (DP), and only small area of the original Atlantic Forest has been preserved in tropics, implying that actions must be taken by the livestock sector to improve sustainability. Intensification makes it possible to produce the same amount, or more beef, in a smaller area; however, the environmental impacts must be assessed. Regarding climate change, the C dynamics is essential to define which beef cattle systems are sustainable. The objectives of this study were to investigate the C balance (t CO2e./ha per year), the intensity of C emission (kg CO2e./kg BW or carcass) and the C footprint (t CO2e./ha per year) of pasture-based beef cattle production systems, inside the farm gate and considering the inputs. The results were used to calculate the number of trees to be planted in beef cattle production systems to mitigate greenhouse gas (GHG) emissions. The GHG emission and C balance, for 2 years, were calculated based on the global warming potential (GWP) of AR4 and GWP of AR5. Forty-eight steers were allotted to four grazing systems: DP, irrigated high stocking rate pasture (IHS), rainfed high stocking rate pasture (RHS) and rainfed medium stocking rate pasture (RMS). The rainfed systems (RHS and RMS) presented the lowest C footprints (−1.22 and 0.45 t CO2e./ha per year, respectively), with C credits to RMS when using the GWP of AR4. The IHS system showed less favorable results for C footprint (−15.71 t CO2e./ha per year), but results were better when emissions were expressed in relation to the annual BW gain (−10.21 kg CO2e./kg BW) because of its higher yield. Although the DP system had an intermediate result for C footprint (−6.23 t CO2e./ha per year), the result was the worst (−30.21 CO2e./kg BW) when the index was expressed in relation to the annual BW gain, because in addition to GHG emissions from the animals in the system there were also losses in the annual rate of C sequestration. Notably, the intensification in pasture management had a land-saving effect (3.63 ha for IHS, 1.90 for RHS and 1.19 for RMS), contributing to the preservation of the tropical forest.