Reducing GHG emissions from livestock

Reducing meat and dairy consumption would help reduce greenhouse gas (GHG) emissions from farming. A recent study describes the 'ecological leftovers' approach to reducing livestock-related GHGs, which assumes that a sustainable number of livestock can be calculated on the basis of available marginal land, unsuitable for other purposes, and available agricultural by-products, which could be used as feed.

Increased resources are needed to support a growing global population, forecast to reach 9 billion by 2050, by which time global demand for meat and milk products are predicted to be twice today's levels. Set against this is the need to cut GHG emissions in the fight against climate change. Meat and dairy products contribute significantly to GHG levels.

Life-cycle analysis (LCA) is often used to examine a product's impact on the environment at all stages of production, use and disposal. However, the study argues that the impact of rearing livestock should be examined in a wider context than that identified by LCA in order to account for a globalised, highly complex food system.

For example, there are second order impacts, not currently included in standard LCA, which consider land use change over time. Land use change would release carbon if forest is cleared to make way for agricultural land. There are also 'opportunity costs', such as the consequences of using land to rear livestock and grow cereals for livestock feed instead of using it to growing cereals for direct human consumption or for energy production. There is also a needs-based approach, which sets limits on demands related to people's actual needs. What constitutes 'needs' is open to debate.

The research focuses on two ways to reduce GHG emissions from livestock: improving productivity and reducing the number of livestock. Although improved productivity can be achieved through changes in diet, such as feeding animals with greater levels of concentrates, such as cereals and oilseeds, the consequences could be counter-productive, as more land would be needed to grow these feedstuffs. Mitigation models suggest that changes in diet, combined with other management measures, could reduce emissions from livestock farming by 25-30 per cent by 2020 in the UK.

Reducing the number of livestock implies cutting consumption. The study identifies three ways this could be achieved:

  1. Reducing consumption in developed countries so that it matches levels projected for those living in developing countries by 2050. This is anticipated to be 44kg of meat and 78kg of milk per person per year. Globally, this will cut meat consumption by 15 per cent and milk consumption by 22 per cent. However, even these cuts would not be sufficient as global demand is expected to be 70 per cent higher for meat and 45 per cent for milk, compared to 2000 levels, as demand from developing and transitional countries increases.
  2. Keeping meat and dairy production for all at 2000 global average levels. This means that by 2050, each person would consume about 25kg of meat and 53kg of milk a year (about the same as consumed in the developing world today). However, this would still not reduce GHG emissions unless there are greater technical and managerial innovations.
  3. The 'ecological leftovers' approach, where livestock production and consumption are adapted and constrained so that they meet ecological limits. Livestock would be only raised on marginal land, unsuitable for other purposes, and fed only on genuine by-products such as vegetable residues. This approach leads to genuine GHG benefits, since the higher methane emissions per unit of milk or meat produced will be outweighed by the significant absolute reduction in numbers. This scenario leads to a sustainable level of consumption which is lower than any of the figures given in scenarios 1 and 2.

The study suggests the full range of policy tools is needed to achieve reductions - fiscal, regulatory and voluntary. It also makes recommendations for further research, including: introducing suitable breeding programmes to develop livestock suited to grazing on marginal land and assessing diets that provide maximum nutrition with minimal GHGs.

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