A major challenge for agriculture in the early years of the 21st century is to develop cropping systems better able to cope with continuing climate change. These new systems must also be more sustainable and so must have fewer negative environmental effects. An element of such new systems could be the introduction of greater genetic diversity in our crops. Diversity can be viewed at different levels: genetic diversity, species diversity, and functional diversity. These will likely interact synergistically to increase the benefits gained beyond a simple additive function. Various examples will be given to illustrate how diversity within and among species may provide increased stability of biomass production and improved ecosystem services. The introduction of greater diversity to agroecosystems appears to be a promising way in which production systems may better adapt to climate change. It is also important we work to combine knowledge from a number of different research fields to design optimal mixtures of species and genotypes and improved ecosystem services.