Background/Question/Methods In the face of decreasing biodiversity and growing concerns about climate change and other global changes, maintaining ecosystem functioning is seen both as a means to preserve biological diversity as well as for safeguarding human wellbeing by securing the services which the ecosystems provide. Although this idea is important, the concept of ecosystem functioning itself remains rather vague and elusive. On the other hand, most ecologists and conservation biologist share the intuitive feeling that the notion of “ecosystem functioning” is something useful and important. If ecosystems are more than a haphazard assemblage of objects and processes, the concept of the functioning of ecosystem should be something meaningful and also something which we should be able to apply in practice. This is also shown by the fact that a large number of ecological studies (especially relating to biodiversity and ecosystem functioning), but also many conservation strategies (such as the Ecosystem Approach of the Convention on Biological Diversity) deal with this issue. Thus the question arises how we can conceptualize and measure “ecosystem functioning” in a meaningful way.

Results/Conclusions As will be shown in this presentation, tackling these questions – and applying them to the practice of ecology and conservation biology – requires more than empirical scientific work and theoretical discussions. “Ecosystem functioning” means different things to different scientists. One reason for this is given by the fact that ecosystem and their reference states (or their reference dynamics) are not “given” by nature as such. Thresholds for deciding as to whether an ecosystem is functioning or if it is not are based in part also on societal decisions and on philosophical assumptions on the “nature” of ecosystems and the purposes they are supposed to fulfill. This partial dependence of the meaning of “ecosystem functioning” on societal choices is, however, less a problem, but more a chance or even part of the solution of the problem to assess the functioning of ecosystems (in its different meanings). Taking into account the societal context of ecological research and environment policy strategies allows creating a useful classification of the “functioning” of ecosystems and to operationalize it. As part of this, we have to strive for modes of a better mutual “translation” between scientific and non-scientific ideas about ecosystems and nature