The livestock sector is the largest source of anthropogenic methane
emissions, and is projected to increase in the future with increased
demand for livestock products. Here, we compare livestock methane
emissions and emission intensities, defined by the amount of methane
emitted per unit of animal proteins, estimated by different
methodologies, and identify mitigation potentials in different regions
of the world based on possible future projections. We show that emission
intensity decreased for most livestock categories globally during
2000-2018, due to an increasing protein-production efficiency, and the
IPCC Tier 2 method should be used for capturing the temporal changes in
the emission intensities. We further show that efforts on the
demand-side to promote balanced, healthy and environmentally-sustainable
diets in most countries will not be sufficient to mitigate livestock
methane emissions without parallel efforts to improve production
efficiency. The latter efforts have much greater mitigating effects than
demand-side efforts, and hence should be prioritized in a few developing
countries that contribute most of the mitigation potential.