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Keywords:

  • ecosystem function;
  • human pressure;
  • landscape trajectories;
  • nature and culture;
  • process-based restoration;
  • reference functioning;
  • reference state;
  • Water Framework Directive

Abstract

In the last two decades river restoration has become increasingly a field of research asking a series of complex questions related not just to science but also to society. Why should we restore ecosystems? Is restoration always beneficial? When is it beneficial? What should be the target reference states? What is success and when can it be evaluated? Our objective is to chronicle and discuss the fundamental concepts of reference versus objective, state versus process-based actions, nature versus culture and ecosystem integrity versus ecosystem benefits driven restoration.

We discuss the dynamic and yet unresolved definition of a reference state. Although the desire to re-create the past is tempting, science has shown that river systems follow complex trajectories frequently making it impossible to return to a previous state. Therefore, restoration goals are moving away from explicitly defining a reference state because of the difficulty of attaining that reference state. We argue that the reference-based strategy should be progressively replaced by an objective-based strategy that reflects the practical limitations of developing sustainable landscapes and the emerging importance of accounting for human services of the target ecosystem. After a decade during which natural processes have been the focus of restoration, it appears that particular processes are not equally valuable everywhere and that regional complexity must be better understood to adjust restoration actions. Copyright © 2009 John Wiley & Sons, Ltd.