Enteric methane emissions and their response to agro-ecological and livestock production systems dynamics in Zimbabwe

Without disregarding its role as one of the key sources of sustainable livelihoods in Zimbabwe and other developing countries, livestock production contributes significantly to greenhouse gas (GHG) emissions through enteric fermentation. For the livestock sector to complement global efforts to mitigate climate change, accurate estimations of GHG emissions are required. Methane emissions from enteric fermentation in Zimbabwe were quantified over 35years under four production systems and five agro-ecological regions. The Intergovernmental Panel on Climate Change emission factor methodology was used to derive CH₄ emissions from seven livestock categories at national level. Emission intensities based on human population, domestic export of livestock meat and climate variables were used to assess emission drivers and predict future emission trends. Over the past 35years, enteric fermentation CH₄ emissions from all livestock categories ranged between 158.3 and 204.3Ggyear⁻¹. Communal lands, typified by indigenous livestock breeds, had the highest contribution of between 58% and 75% of the total annual emissions followed by livestock from large scale commercial (LSC) farms. The decreasing livestock population on LSC farms and consequent decline in production could explain the lack of a positive response of CH₄ emissions to human population growth, and decreasing emissions per capita over time at −0.3kg CH₄capita⁻¹year⁻¹. The emissions trend showed that even if Zimbabwe's national livestock population doubles in 2030 relative to the 2014 estimates, the country would still remain with similar magnitude of CH₄ emission intensity as that of 1980. No significant correlations (P>0.05) were found between emissions and domestic export of beef and pork. Further research on enhanced characterisation of livestock species, population and production systems, as well as direct measurements and modelling of emissions from indigenous and exotic livestock breeds were recommended.