摘要：With a bang or with a whimper? A number of studies address this key question related to the ways in which ecosystems degrade. Our angle is slightly different. In this essay, we discuss what challenges the possibility of abrupt change poses to environmental policy. As a reference, we use the concept of an ecological threshold which describes how systems can change dramatically from one state to another. Environmental experts have recognized the usefulness of the concept. Both conceptual understanding and empirical evidence from different ecosystems suggest negative and irreversible consequences of trespassing ecological thresholds. However, large gaps remain regarding how to use the concept to prevent negative or enhance positive changes. This observation motivated our review of key features of the threshold concept in order to discuss its use in policy. We draw especially on studies describing European coastal areas. We conclude that, particularly because thresholds cannot be identified and legally defined once and for all, a continuous learning process is critical. We also stress that societies will have to develop diagnostics that support such learning processes.
