Preserving global land and water resources through the replacement of livestock feed crops with agricultural by-products

While animal-source foods contribute to 16% of the global food supply and are an important protein source in human diets, their production uses a disproportionately large fraction of agricultural land and water resources. Therefore, a global comprehensive understanding of the extent to which livestock production competes directly or indirectly with food crops is needed. Here we use an agro-hydrological model combined with crop-specific yield data to investigate to what extent the replacement of some substitutable feed crops with available agricultural by-products would spare agricultural land and water resources that could be reallocated to other uses, including food crop production. We show that replacing 11–16% of energy-rich feed crops (that is, cereals and cassava) with agricultural by-products would allow for the saving of approximately 15.4–27.8 Mha of land, and 3–19.6 km3 and 74.2–137.8 km3 of blue and green water, respectively, for the growth of other food crops, thus providing a suitable strategy to reduce unsustainable use of natural resources both locally or through virtual land and water trade.