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Special PresentationsBiodiversity: a central concept in organic agriculture F6Altieri, Miguel1; Wolfe, Martin2. 1) Agroecology, Berkley University, 1050 San Pablo Ave., Albany, California. 2)Institute of Plant Sciences, Swiss Federal Institute of Technology, CH-8092 Zurich, Switzerland |
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| The development of production-orientated agriculture maximised monoculture of few species and few varieties and selection and evolution of pests, pathogens and weeds. Control of these problems has depended on the use of resistant varieties and pesticides, but both of these approaches are under constant threat from further adaptation of pests, pathogens and weeds. A central strategy in sustainable agriculture is to restore biodiversity of the agricultural landscape in the form of polycultures, agroforestry patterns, diversified field boundaries, etc. A major reason to maintain and enhance biodiversity in agroecosystems is that it performs a variety of ecological services, including regulation of insect pests, pathogens and weeds. When these natural services are lost due to biological simplification, the economic and environmental costs can be significant. In modern agroecosystems, experiments indicate that biodiversity can be used to improve insect pest management. Insect pest populations can be stabilized when designing diversified cropping systems that support populations of natural enemies or that have direct deterrent effects on pest herbivores. Other experiments show that only a small increase in within-field diversity, through the use of simple variety mixtures, is sufficient to delay development of many air-borne diseases. This approach can provide a stable buffer against stress on a regional scale. Diversity at the species level, in the form of crop rotation, is a basic element in organic agriculture, particularly for the control of soil-borne diseases and weeds. Other forms of inter-cropping are of current importance in tropical agriculture and of potential importance in temperate agriculture. Examples involving legumes with other annual and perennial crops will be discussed. The ultimate biodiversity is represented by forms of agroforestry, which integrate the principles described above. Agroforestry presents an exciting potential for the development of organic agriculture as a whole and not only for restriction of pests, pathogens and weeds. | |||
