Clearly, when attempting to develop criteria for the assessment of biodiversity the first priority is to know what these criteria are supposed to measure. Some have said in this conference that we all know what we mean when we speak of biodiversity. They exemplify the extreme fuzziness of the concept as it is presently employed. Let me make some remarks on this issue.
Biodiversity is a property of a particular geographic area.
The first question is thus which areas are to be considered. From a scientific point of view speaking of the biodiversity of e.g. Northern Europe necessarily leads to errors and only the notion of the Earth's biodiversity makes sense. Biodiversity is measured in particular units. In order to be able to select the correct measure of biodiversity we must consider how the concept is used. First it has to be established that the employed units are the correct ones in the context of the problem.