Strategies for future robust meat production and climate change mitigation under imported input constraints in Alentejo, Portugal

International audience; The Alentejo region in Portugal is vital to the country's beef industry and is home to 60% of the Portuguese beef cattle population. Farmers increasingly rely on imported synthetic fertilizer and feed. The uncertainty of global oil supply and indirect inputs calls into question the robustness of the beef farming system in Alentejo, defined as the capacity of the system to maintain its function (beef production) in spite of a disturbance (decreased input availability). An additional challenge is the need for reducing greenhouse gas emissions to meet decarbonization goals. At present, these challenges are being addressed through management practices such as expanding areas of high-yield sown biodiverse pastures and fattening steers partially on grass rather than concentrates. These practices have been shown to reduce greenhouse gas emissions, but their effect on the robustness of beef production when inputs are scarce is unknown. To fill this gap, we adapted a dynamic nitrogen mass flow model to assess herd dynamics and calculate a greenhouse gas emissions balance. We applied the model for seven scenarios corresponding to different combinations of management practices over 50 years with increasing input constraints. We estimated, without changes and without constraints, a greenhouse gas balance of 55 kgCO(2)-e kg carcass(-1) year(-1) (100-years global warming potential). Without changes but faced with constraints, meat production dropped 60% (low long-term robustness) in 50 years while increasing by 17% the greenhouse gas balance. Our results showed that a combination of high-yield legume-rich pastures, maximization of grass intake, herd size reduction, and increased animal productivity allowed the smallest reduction of meat production (28%) and largest greenhouse gas emission reduction (30%, i.e., 38.9 kgCO(2)-e kg carcass(-1) year(-1)). This was the best, among the combination studied, at mitigating the trade-off between robust meat production and climate change mitigation.