A Scientific Review of the Impact of UK Ruminant Livestock on Greenhouse Gas Emissions

Climate change is a subject of global environmental concern. The UK has seen a progressive strengthening of political resolve to address the problems associated with emissions of greenhouse gases (GHGs), principally carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Although agriculture globally, and ruminant livestock production in particular, is a net contributor to GHG emissions, generalizations about impacts on climate change often fail to distinguish between different systems of production, advances in technology, and the role of extensive grazing lands in contributing to ecological services and food production in situations where other forms of farming are impractical. Against this background, the overall aim of this review was therefore to conduct an independent desk-based analysis of the scientific evidence of the impacts of the UK’s forage-based livestock sectors (beef, sheep and dairy production) on emissions of the three main GHGs: carbon dioxide, methane and nitrous oxide. The study has been confined to impacts up to the ‘farm gate’ and it has examined and reviewed the evidence to answer the following questions: How do GHG emissions from UK beef, sheep and dairy production compare with the situation in other countries/regions, such as South America and NZ, and selected EU countries. Within the UK how do various intensive and extensive systems of dairy, beef cattle and sheep production compare in terms of their respective emissions balances? What are the research findings on measures that can or have been adopted to reduce net GHG emissions, and what is the potential for further adoption by the industry in the UK? What are the likely future impacts of climate change on the UK ruminant livestock industry, particularly in comparison with its competitors? Main findings: Total UK agricultural GHG emissions have decreased by 17% since 1990. Methane (CH4) emissions have decreased by 52% since 1990, through a combination of reduced livestock numbers and more efficient feeding. There is evidence that UK ruminant agriculture compares favourably with other countries, and that the rate of reduction of total agricultural GHGs in the UK in recent years has been similar to, or greater than, several competitor countries. There is a wide degree of uncertainty over the exact levels of emissions of N2O and evidence suggests that UK emissions are lower than those based on the IPCC methodology. The development of more precise GHG inventories will address these uncertainties. Increases in milk yields and technical feed improvements have been associated with reductions in GHG emissions per litre of milk. The UK beef sector has also benefited from technical feed improvements, and UK beef production, and increasingly also lamb production, is mainly carried out over a short production cycle; this contributes to reducing the GHG emissions per animal and thus per unit of output. Livestock in upland and marginal areas may be associated with high CH4 emissions per unit of output (due to relatively low quality forage) but low emissions per ha. Many of these areas also have a role in CH4 capture, and their management via low intensity beef and sheep grazing is also important in achieving wider agri-environmental objectives.