Moderate reductions in animal protein intake could substantially decrease pressure on environment when food system change is optimised

Diet change towards less animal protein is often proposed as one of the key opportunities to produce more food with less natural resources. However, depending on how feed is provided, part of the livestock production could be sustainable – but how large a part remains to be answered. The key challenge has been that the existing methods assessing the impacts of altering the level of animal protein in diets rely on static use of resources, and do not take into account the changes needed in entire food system; including the use of by-products for feed, how efficiently the replacing plant-based protein could be produced with land freed from feed production or pasture, etc. We developed an integrated global food system model “Aalto OptoFood” that allows us to assess dynamically the response of these scenarios on different parts of the food system, and thus optimise the diet transition from the point of view of resource use. We show that even moderate decrease in animal protein consumption can yield a substantial reduction in, here, water consumption. Reductions of one-fifth in livestock protein would decrease water consumption by 24-26%; 60-79% of total reduction potential and 3-5 times more than an estimate using the existing static methods. Water consumption levels off after 40-50% cut in animal protein intake, indicating that part of the meat consumption may be sustainable from a water perspective. These results are driven by dynamics between food production sectors and show the importance of non-food animal feeds, highlighting the need to use an integrated systemic approach in food system studies.