THE NEED TO STUDY AND MANAGE VARIATION IN AGROECOSYSTEMS

Variation within agro-ecosystems is a universal but complex phenomenon which is present in each of the factors that determine the agro-ecosy stem, i.e. the environment, genetic resources and management. Agrodive rsity is defined as the variation resulting from the interaction betwe en these factors. This variation manifests itself in many different fo rms, at different scales and levels of aggregation. Examples show that poor management of agrodiversity in high and low external input agric ulture reduces output, output stability, resource-use efficiency and t he production potential of the natural resource base. A better underst anding of agrodiversity is required to improve its management. Also, a nalysis of variation in agroecosystems requires other approaches in re search to be further developed in order to characterise, measure, and understand relevant variation.