Assessing the environmental impact of sheep production

Sheep are reared under a wide range of conditions globally and in a high diversity of systems ranging from extensive browsing systems through to full housing with brought-in feeds. Additionally, they are often farmed in systems with multiple products including other animals (e.g. beef cattle or goats), arable crops and/or trees. Thus, there is considerable variability in the extent of resource use associated with sheep farming and production of live weight for meat production and wool, as well as in their environmental impacts. Environmental impacts can include effects on water, air and soil quality. Some impacts such as the effects on water quality are important at a local or site-specific level, while other impacts such as from greenhouse gas (GHG) emissions are global. Sheep production systems can also have a wider impact on resource status (e.g. biodiversity), human health via various pollutants, and community and cultural well-being. Life cycle assessment (LCA) is a tool that is used to quantify multiple resource use and environmental impacts, which can be applied at different scales from farm level through to full life cycle, that is, from extraction of raw materials for inputs, through to farm production, processing, retailing, consumption and waste stages (ISO, 2006). At a life cycle level, the impacts are expressed per kg of product, for example meat or wool (or, e.g., per-kg lamb leg roasted for eating or per m2 of carpet over a lifetime of use). Evaluation of the LCA of sheep products through to markets is important, as large quantities of sheep products are traded globally; for example, New Zealand (NZ) exports over 90% of its lamb production to many countries around the world. Assessment throughout the life cycle enables determination of the relative contribution from different stages, so that the dominant contributing stages can be identified (‘hot spots’) and targeted for mitigation. With the increasing demand for food globally, there has been increased pressure on land availability for food production. This rise in demand has often been associated with agricultural intensification, which has generally required an increase in external inputs (e.g. fertilisers, water), animal stocking rates and productivity, with the potential for greater effects on the environment. While sheep farming is relatively more extensive than many other livestock systems, sheep farms are gradually being intensified, and LCA can provide a full picture of the changes in resource use and environmental impacts. This chapter reviews the environmental impacts of sheep production systems at a farm level and then expands on this topic to cover the environmental impacts of sheep products (meat and wool) throughout their life cycle. A case study is presented for sheep products from French and NZ farm systems to illustrate the hot spots for environmental emissions.