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Attempts to assess the functional importance of biodiversity in ecosystems continue to stimulate debate on the potential impacts of biodiversity losses. However, finding experimental setups to realistically simulate current and anticipated species loss turns out to be surprisingly difficult. Uncertainties concern the relevance of the present empirical evidence for large-scale natural and agricultural situations and the relation between observed specific processes and ecosystem services that provide a basis for human life support. Since ecosystem effects of biodiversity loss may be experimentally less tractable than other global change issues we were interested in current expert opinions. The resulting survey provides what might be the best-available answers to urgent questions regarding the certainties and uncertainties of the functional role of biodiversity in ecosystems. The respondents generally expected that: (1) ecosystem process rates are strongly correlated with biological diversity, and (2) these same processes are (although to a varying extent) important for the delivery of humanly defined ecosystem services by natural systems. The survey thus suggests caution in reducing ecosystem-level biodiversity, but it also underscores the opportunities for land management that may arise from the recognition of biodiversity effects in ecosystems. A caveat regards the possible bias of participants toward scientists who are particularly concerned about environmental change.
Felix Schläpfer (1999) studied this question.