Can positive interactions between cultivated species help to sustain modern agriculture?

The importance of positive interactions between species within natural ecosystems and species associated with traditional agriculture is well recognized. However, modern agriculture generally depends on monocultures, where positive interactions between cultivated species (ie in which the presence of one species facilitates the survival, growth, or reproduction of other species) are largely ignored. Here, we review recent studies focused on the positive interactions between cultivated species, consider how three traditional agricultural systems (legume-cereal intercropping, rice-fish co-culture, and agroforestry) have benefited from such interactions, and examine how these benefits are affected by climate, planting patterns, and field management. Finally, we propose a framework to illustrate how these interactions may improve modern agriculture through: the selection of species-species partnerships; the development of specialized field machinery (in each case); field structure and configuration; field management; and farmer and societal acceptance.