Greenhouse gas emissions, land use, water use, water pollution and biodiversity impact of vegans, vegetarians, fish-eaters and meat-eaters in the UK

Modelled estimates of the environmental burden associated with low meat consumption suggest that substantial benefits could accrue from shifts in diet. However, modelled dietary scenarios may not reflect true dietary practice and have not previously accounted for variation in the environmental burden of food due to sourcing and production methods. We link dietary data from a sample of 55,504 vegans, vegetarians, fish-eaters and meat-eaters with food-level data on greenhouse gas emissions (CO2, CH4 and N2O and three aggregated measures of CO2 equivalents), land use, water use, eutrophication risk and potential biodiversity loss from a review of 570 life cycle assessments covering more than 38,000 farms in 119 countries. By conducting Monte Carlo analyses drawing from food-level distributions of the environmental indicators that are due to variations in sourcing and production methods we estimate both mean impact and 95% uncertainty intervals for each diet group. We find that for all of the environmental indicators there is a positive association with amount of animal-based food consumed. Dietary impacts for vegans were 25.1% (95% uncertainty interval: 15.1% - 37.0%) of high meat-eaters (>=100g total meat consumed per day) for greenhouse gas emissions, 25.1% (7.1% - 44.5%) for land use, 46.4% (21.0% - 81.0%) for water use, 27.0% (19.4% - 40.4%) for eutrophication and 34.3% (12.0% - 65.3%) for biodiversity. Large differences (at least 30% for GHG emissions, eutrophication, and land use) in the environmental impact of diets are also observed between low (<50g/d) and high meat-eaters. Although there is substantial variation in environmental indicators due to where and how food is produced, the resultant uncertainty does not obscure the strong relationship between animal-based food consumption and environmental impact. Debate about sourcing and production of foods should therefore not prevent action aimed at reducing consumption of animal-based foods.