Agriculture is the largest single source of global anthropogenic methane (CH 4 ) emissions, with ruminants the dominant contributor. Livestock CH 4 emissions are projected to grow another 30% by 2050 under current policies, yet few countries have set targets or are implementing policies to reduce emissions in absolute terms. The reason for this limited ambition may be linked not only to the underpinning role of livestock for nutrition and livelihoods in many countries but also diverging perspectives on the importance of mitigating these emissions, given the short atmospheric lifetime of CH 4 . Here, we show that in mitigation pathways that limit warming to 1.5°C, which include cost-effective reductions from all emission sources, the contribution of future livestock CH 4 emissions to global warming in 2050 is about one-third of that from future net carbon dioxide emissions. Future livestock CH 4 emissions, therefore, significantly constrain the remaining carbon budget and the ability to meet stringent temperature limits. We review options to address livestock CH 4 emissions through more efficient production, technological advances and demand-side changes, and their interactions with land-based carbon sequestration. We conclude that bringing livestock into mainstream mitigation policies, while recognizing their unique social, cultural and economic roles, would make an important contribution towards reaching the temperature goal of the Paris Agreement and is vital for a limit of 1.5°C. This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 1)'.

No abstract

Diets link human health with environmental sustainability, offering promising pressure points to enhance the sustainability of food systems. We investigated the health, environmental, and economic dimensions of the current diet in Argentina and the possible effects of six dietary change scenarios on nutrient adequacy, dietary quality, food expenditure, and six environmental impact categories (i.e., GHG emissions, total land occupation, cropland use, fossil energy use, freshwater consumption, and the emission of eutrophying pollutants). Current dietary patterns are unhealthy, unsustainable, and relatively expensive, and all things being equal, an increase in income levels would not alter the health dimension, but increase environmental impacts by 33–38%, and costs by 38%. Compared to the prevailing diet, the six healthier diet alternatives could improve health with an expenditure between + 27% (National Dietary Guidelines) to -5% (vegan diet) of the current diet. These dietary changes could result in trade-offs between different environmental impacts. Plant-based diets showed the lowest overall environmental impact, with GHG emissions and land occupation reduced by up to 79% and 88%, respectively, without significant changes in cropland demand. However, fossil energy use and freshwater consumption could increase by up to 101% and 220%, respectively. The emission of eutrophying pollutants could increase by up to 54% for all healthy diet scenarios, except for the vegan one (18% decrease). We conclude that the health and environmental crisis that Argentina (and other developing countries) currently face could be mitigated by adopting healthy diets (particularly plant-based), bringing in the process benefits to both people and nature. Supplementary Information The online version contains supplementary material available at 10.1007/s11625-021-01087-7.

No abstract