Many livestock and aquaculture feeds compete for resources with food production. Increasing the use of food system by-products and residues as feed could reduce this competition. We gathered data on global food system material flows for crop, livestock and aquaculture production, focusing on feed use and the availability of by-products and residues. We then analysed the potential of replacing food-competing feedstuff—here cereals, whole fish, vegetable oils and pulses that account for 15% of total feed use—with food system by-products and residues. Considering the nutritional requirements of food-producing animals, including farmed aquatic species, this replacement could increase the current global food supply by up to 13% (10–16%) in terms of kcal and 15% (12–19%) in terms of protein content. Increasing the use of food system by-products as feed has considerable potential, particularly when combined with other measures, in the much-needed transition towards circular food systems.

Although the role of livestock in future food systems is debated, animal proteins are unlikely to completely disappear from our diet. Grasslands are a key source of primary productivity for livestock, and feed‐food competition is often limited on such land. Previous research on the potential for sustainable grazing has focused on restricted geographical areas or does not consider inter‐annual changes in grazing opportunities. Here, we developed a robust method to estimate trends and interannual variability (IV) in global livestock carrying capacity (number of grazing animals a piece of land can support) over 2001–2015, as well as relative stocking density (the reported livestock distribution relative to the estimated carrying capacity [CC]) in 2010. We first estimated the aboveground biomass that is available for grazers on global grasslands based on the MODIS Net Primary Production product. This was then used to calculate livestock carrying capacities using slopes, forest cover, and animal forage requirements as restrictions. We found that globally, CC decreased on 27% of total grasslands area, mostly in Europe and southeastern Brazil, while it increased on 15% of grasslands, particularly in Sudano‐Sahel and some parts of South America. In 2010, livestock forage requirements exceeded forage availability in northwestern Europe, and southern and eastern Asia. Although our findings imply some opportunities to increase grazing pressures in cold regions, Central Africa, and Australia, the high IV or low biomass supply might prevent considerable increases in stocking densities. The approach and derived open access data sets can feed into global food system modelling, support conservation efforts to reduce land degradation associated with overgrazing, and help identify undergrazed areas for targeted sustainable intensification efforts or rewilding purposes.

Several safe boundaries of critical Earth system processes have already been crossed due to human perturbations; not accounting for their interactions may further narrow the safe operating space for humanity. Using expert knowledge elicitation, we explored interactions among seven variables representing Earth system processes relevant to food production, identifying many interactions little explored in Earth system literature. We found that green water and land system change affect other Earth system processes strongly, while land, freshwater and ocean components of biosphere integrity are the most impacted by other Earth system processes, most notably blue water and biogeochemical flows. We also mapped a complex network of mechanisms mediating these interactions and created a future research prioritization scheme based on interaction strengths and existing knowledge gaps. Our study improves the understanding of Earth system interactions, with sustainability implications including improved Earth system modelling and more explicit biophysical limits for future food production.

A considerable amount of food produced is lost globally. Food loss indicates not only the amount of edible food that humans do not consume but also the waste of resources used in production and distribution, linked with multifold problems such as climate change, biodiversity loss, and economic loss. While there has been a growing body of literature about magnitudes and technical solutions to reduce food loss, little is known about how different socioeconomic factors are potentially related to the losses. Here we assess the relationships between various relevant socioeconomic factors and food loss within the early stages of the food supply chain (i.e., farm, harvest, storage, and transport parts of it) using the most comprehensive data available. We found that factors such as high gross national income (GNI) per capita and high employment in agriculture are significantly associated with low food loss. It suggests that income might be invested in technology or infrastructure while labor is still vital to reduce food loss, especially in technology-inferior countries. Other important factors related to low food loss are access to electricity in rural areas and export volume index, although the significance and directions vary in each commodity and food supply stage. Our results provide valuable insights into socioeconomic factors around food loss that are beneficial to formulating relevant policy, especially in countries where substantial food losses in the early stages of the food supply chain considerably risk to food security.

The production and consumption of animal-source foods must be transformed to mitigate negative environmental outcomes, including greenhouse gas emissions and land-use change. However, livestock are also key for food production and for livelihoods in some settings, and they can help preserve biodiversity and certain ecosystems. Previous studies have not yet fully explored sustainability limits to the use of grazing lands for food production in the context of biodiversity. Here we explore ‘biodiversity limits’ to grassland ruminant production by estimating the meat and milk production from domestic ruminants limited to grazing areas and stocking densities where livestock can contribute to the preservation or restoration of biodiversity. With biodiversity-friendly grazing intensities at 0–20% biomass removal depending on aridity, this take on biodiversity limits corresponds to 9–13% and 26–40% of the current grassland-based milk and meat production, respectively. This equals only 2.2 kg of milk and 0.8 kg of meat per capita per year, globally, but altered management and moving from meat-specialized to meat-and-dairy systems could increase the potential production while still remaining within this approach to biodiversity limits.