Research and policies aimed at biodiversity conservation in agricultural ecosystems are often less successful than expected. One common assumption is that more research is needed to develop improved measures and indicators of biodiversity. The authors’ opinion is that this is only partly true and that most of the problems arise from the lack of a well-focussed approach to this subject. Based on the knowledge available in the scientific literature, a methodological framework was developed which can help researchers and policy makers to think in a better, more structured way about issues related to biodiversity conservation in a given agroecosystem. In order to frame the importance of biodiversity in agroecosystems, three main questions were addressed through literature search: (1) What does biodiversity mean in natural and agricultural ecosystems? (2) How is the concept of functionality used in relation to biodiversity? (3) Which biodiversity measures are currently used to express agriculture–biodiversity relationships?
Analysis of the literature resulted in a framework consisting of three steps. At first the objectives of biodiversity research and policies have to be defined. Three options can be foreseen here: (a) species, community, habitat or overall biodiversity conservation regardless of its functions, (b) biodiversity conservation to attain production and environmental protection services, and (c) use of bio-indicators for agroecosystem monitoring. In the second step the appropriate target elements for conservation have to be chosen based on an agroecosystem approach, and in the third step adequate biodiversity measures of composition, structure and function have to be selected for each target element.
Functional biodiversity is important in relation to the provision of specific agroecosystem services. The study of functional biodiversity should start with the definition of agroecosystem functional groups comprising all elements that interact with the desired service, and the consequent determination of the role of diversity within these functional groups for the fulfilment of the agroecosystem service. Therefore a more precise definition of ‘functional biodiversity’ would be “that part of the total biodiversity composed of clusters of elements (at the gene, species or habitat level) providing the same (agro)ecosystem service, that is driven by within-cluster diversity”.