Livestock provide as much as one-third of all protein consumed by humans, but have a disproportionate and growing environmental impact. Livestock production occupies 50-75% of agricultural land, contributes 15% of anthropogenic greenhouse gas emissions, and drives agricultural expansion in the tropics through the global trade in animal feed. This thesis therefore evaluates two strategies for shrinking the environmental impact of the livestock sector.

First, I evaluate the potential for food losses (i.e. foods which were intended for human consumption, but which ultimately are not directly eaten by people) to replace grain- and soybean-based pig feeds in Europe. While food losses have been included in animal feed for millennia, the practice is all but banned in the European Union, because of disease control concerns. Several East Asian states have in the last 20 years, however, introduced regulated systems for safely recycling food losses into animal feed. I combine data from multiple sources (including government reports, the animal science literature, and factory-floor data from South Korean swill-feed factories), and find that the introduction of East Asian practices for recycling food losses as animal feed could reduce the land use of EU pork (20% of world production) by one fifth, potentially saving 1.8 million hectares of agricultural land. This would also reduce 12/14 other assessed environmental impacts and deliver economic savings for pig farmers, as swill (cooked food losses) costs 40-60% less than conventional grain-based feeds. In a survey of pig farmers (n=82) and other agricultural stakeholders (n=81) at a UK agricultural trade fair, we found high support (>75%) for the relegalisation of swill. Support for swill feeding arose in part because respondents thought that swill would lower costs, increase profitability, and be better for the environment. Our results also confirmed the critical importance of disease control and consumer communication when considering relegalisation, as respondents who thought that swill would increase disease risks and be unpalatable to consumers were less supportive of relegalisation. Any new system for the use of swill will require careful design of regulation to ensure that heat-treatment is sufficient, and to reduce to a negligible level the risk of uncooked animal by-products entering feed. Our results suggest, however, that if such a system can be established, there would be multiple benefits and widespread support for its relegalisation.

Second, I evaluated the potential to increase the productivity of cattle ranching in the Brazilian Amazon. While high hopes have been placed on the potential for intensification of low-productivity cattle ranching to spare land for other agricultural uses, cattle productivity in the Amazon biome (29% of the Brazilian cattle herd) remains stubbornly low, and it is not clear how to realize theoretical productivity gains in practice. I therefore (a) surveyed six on-the-ground initiatives which have been working with local farmers to improve cattle ranching, quantifying their farm practices, animal performance, and economic results; and (b) analysed the progress that has already been made in reconciling agriculture and forest conservation, by evaluating the impact of the flagship anti-deforestation policy, the priority list (Municípios Prioritários). The survey showed that cattle intensification initiatives operating in four states have used a wide range of technologies to improve productivity by 30-490%, while supporting compliance with the Brazilian Forest Code. Using two complementary difference-in-difference estimators, I then found no evidence for trade-offs between agriculture and forest conservation under the priority list; instead, reductions in deforestation in priority list municipalities were paired with increases in cattle production and productivity (cattle/hectare). The policy had no effect on dairy or crop production. Together, these results provide real-world evidence that increases in cattle production in Brazil do not need to come at the expense of the country’s remaining native vegetation.