Greenhouse gas emission intensities in extensive beef cattle production systems in the Global South: a systematic review

Extensive beef cattle production systems underpin rural livelihoods across Africa, Asia, and South America, yet they remain a major source of uncertainty in agricultural greenhouse gas (GHG) accounting due to low productivity, data limitations, and methodological inconsistency in data collection. This systematic review synthesises evidence on greenhouse gas emission intensity (GHGEI) from extensive cattle systems in developing regions. The objective is to identify biological and methodological drivers of variation and assess implications for emission measurement and mitigation planning. Following the PRISMA framework, 67 peer-reviewed and grey literature studies published between 2010 and 2025 were analysed, covering functional units, system boundaries, emission quantification methods, allocation approaches, and mitigation interventions. Reported GHGEI values show substantial regional and methodological variability. For meat, emission intensities range from 6.3 to 305.8 kg CO 2 -eq per kg protein in Asia, 8.2 to 94.2 kg CO 2 -eq per kg in South America and the Caribbean, and 6.6 to 279 kg CO 2 -eq per kg in Africa. When expressed per unit of meat protein, values span 63.5 to 307.5 kg CO 2 -eq per kg protein in Asia, 39.8 to 226.5 kg CO 2 -eq per kg protein in South America and the Caribbean, and 50.8 to 387.6 kg CO 2 -eq per kg protein in Africa. For combined meat and milk protein, emission intensities range from 2 to 314 kg CO 2 -eq per kg protein in Asia, 14 to 312 kg CO 2 -eq per kg protein in South America and the Caribbean, and 179 to 295 kg CO 2 -eq per kg protein in Africa. This highlights large differences in productivity, system efficiency, and methodological approaches across regions. Inconsistent functional units, system boundaries, tools for quantifying GHGEI, and allocation methods substantially amplify reported variability. GLEAM-based emission profiles indicate that enteric methane dominates emissions across regions, with land-use change strongly influencing emission intensities in South America. Standardising emission accounting frameworks and improving measurement, reporting, and verification systems are essential for credible mitigation assessment and integration of extensive beef cattle systems into national GHG inventories and climate policy.