Biodiversity and ecosystem functioning: issues of scale and trophic complexity

Research on the relationship between biodiversity and ecosystem functioning is entering a new phase. The main driver behind this is an awareness that biodiversity loss operates at large spatial scales and generally involves reductions and changes in species at different trophic levels simultaneously. Evaluating how ecosystem processes are likely to change following species loss at multiple trophic levels will be difficult because of the feedbacks between levels and between levels and the ecosystem processes of interest. Similarly, carrying out manipulative experiments designed to accommodate multiple trophic levels at the landscape scales in which society is interested will be extremely challenging. Novel approaches, such as the BioMERGE (Biotic Mechanisms of Ecosystem Regulation in the Global Environment) initiative, are needed. In addition, future work should be more services-oriented, rather than process-oriented, if effects of biodiversity change on services are to be properly assessed. Finally, the application of mainstream ecosystem ecology to biodiversity-ecosystem functioning research seems to have been neglected to date. In this respect, there is potential for the mass-balance approach to contribute to the debate.