Potential greenhouse gas emissions mitigation through increased grazing pressure: a case study in North Portugal

Wildfires have been an important process affecting forests and rangelands worldwide. In the Mediterranean region, wildfires burn about half a million hectares of forest and scrubland every year. Fuel loads are the main factor controlling fire risk and its propagation. The reduction of fuel loads by grazing could help to decrease the spread and intensity of wildfires in this region. This study aims to assess the contribution of sheep grazing on fuel load management and their role to the mitigation of wildfire greenhouse gas (GHG) emissions. The methodological approach is based on a simulation of the grazing pressure required to reduce a given quantity of fuel, under the assumption that if it is not consumed, it becomes fuel. Following, a simulation model was designed to estimate the total GHG emissions prevented through grazing, by reducing the risk of fire. These emissions were estimated based on the Intergovernmental Panel on Climate Change (IPCC) framework. The accumulated fuels were estimated to be 3126.65 kg dry matter (DM) ha(-1) and the biomass potentially consumed by sheep was 1416.03 kg DM ha(-1 )yr(-1), corresponding to 45.29% of accumulated fuel loads. Our findings suggest a value of 3.88 sheep ha(-1 )day(-1) as the ideal to reduce 4833.63 kg CO(2)eq ha(-1 )yr(-1) of emissions, distributed between CO2 (-2221.76 kg CO(2)eq ha(-1 )yr(-1); 45.96%), NOx (-1873.41 kg CO(2)eq ha(-1 )yr(-1); 38.76%), CO (-454.55 kg CO(2)eq ha(-1 )yr(-1); 9.40%), CH4 (-186.35 kg CO(2)eq ha(-1 )yr(-1); 3.86%) and N2O (-97.56 kg CO(2)eq ha(-1 )yr(-1); 2%). The results of this study also underline that livestock can help to mitigate climate change in areas prone to wildfires.