This book critically examines the idea that the sustainability of agriculture could be improved by mimicking the structure and processes occurring in natural ecosystems. Researchers from around the world present comparative studies of multi-species farming systems, natural ecosystems and conventional agriculture. Case studies from Europe, Africa, Asia, Australia, and North and South America examine the implications of increasing the complexity of farming systems on water and nutrient cycling, productivity and resilience. Theoretical issues discussed include the role of biodiversity in agriculture, the trade-off between perenniality and productivity, the choice to integrate or segregate production and conservation in an agricultural landscape, and the social and economic challenges to adopting complex farming systems. One section is devoted to the application of this concept in southern Australia, where 15 million hectares of land are expected to be affected by salinity by the middle of the next century unless there is a significant change in agricultural practice.