Minimizing the environmental footprint of livestock production: which measure to use?

A growing and wealthier human population implies an increase in demand for their needs, such as housing, infrastructure, energy and food, including animal-source food. Current animal production levels, however, already pose severe pressure on the environment, via their emissions to air, water and soil, and via their use of scarce and finite resources. The current livestock sector, for example, is responsible for about 15% of the global anthropogenic emission of greenhouse gases, and uses about 70% of all agricultural land. The urgent question arises, therefore, how to reduce the environmental impact of livestock production? To this end, measures to assess the environmental impact of livestock production are essential. In the past, developed measures were generally defined at animal level, i.e. amount of feed used per kg of product produced or the amount of nutrients excreted per kg of product produced. Studies based on such animal-based measures generally conclude that improving animal productivity, in terms of kg of milk per cow per year or number of fattening pigs per sow per year, improves the environmental impact of livestock production. At present, measures derived from a life cycle assessment (LCA) are generally used to assess the environmental impacts of livestock production. Current LCA results demonstrate that production and utilization of feed, and manure management, are dominant factors determining the environmental impact of livestock systems. LCA results demonstrate, for example, that global warming potential, energy use and land use was lower for concentrate-based than for roughage-based beef production. An LCA comparison of beef systems that differ in type of diet, however, is limited because current LCA methodology does not account for competition for land between humans and animals. In case of future land scarcity, therefore, measures should be directed at the entire food system, including the competition for land between humans and animals. Van Zanten et al. (2015) develop such a measure from a land-use perspective, and demonstrated that livestock systems that value marginal land or by-products from the food industry are most efficient. Such systems not necessarily have the highest animal productivity (i.e. lowest feed conversion ratio). Minimizing the environmental footprint of livestock production, therefore, requires a paradigm shift toward the entire food system