Biodiversity challenge: Freshwater ecosystems in the Swiss plateau are threatened by multiple stressors that deteriorate water quality and hydromorphology. To restore these ecosystems and stop the biodiversity decline, multiple management measures will be implemented over the next decades. We propose methods for a spatial and temporal prioritisation to coordinate measures from different sectors and maximise their effectiveness, while considering other societal needs.

Context: Case Study 7 is based in the Swiss Plateau, a relatively flat and densely populated area that facilitates agricultural production and urban development (Fig. 1). Switzerland decided to fund the morphological restoration of one quarter of all morphologically degraded rivers over the next 80 years, to upgrade the 100 most important wastewater treatment plants to remove micropollutants, and to reduce pollution agriculture. Cantonal authorities were asked to provide a strategic plan for the morphological restoration of rivers over the next two decades, which will be updated every 12 years and is intended to increase the effectiveness of restoration measures.

What was done? Using the concepts underlying the AQUACROSS Assessment Framework, we developed a procedure to prioritise restoration measures by maximising the ecological state of a catchment under a given budget constraint, while considering other societal needs and other sources of impairment:

• In close collaboration with stakeholders from federal and cantonal authorities and environmental consulting companies, we integrated procedures for chemical, physical and biological assessment at the river reach scale and proposed a spatially explicit ecological assessment at the catchment scale.
• We applied the catchment scale assessment to search for management strategies that optimise the overall ecological state at the catchment scale, while increasing or not significantly decreasing services (e.g. recreation) demanded by society.

Results: We developed a methodology that supports environmental managers in the integrative assessment of restoration measures at the catchment scale. This methodology is based on ecological principles, such as maximising resilience and fish migration potential and minimising fragmentation. An optimisation procedure provides a set of near-optimal combinations of measures to reach the highest ecological state for a given budget. This list of potential measures can support the development of a cantonal planning, which also requires stakeholder involvement.

Lessons learned for managing biodiversity: Spatial assessment procedures that integrate over different aspects of the ecological state are essential for the prioritisation of restoration measures. The consideration of different types of impairments, such as hydromorphological degradation and chemical pollution, is important to increase effectiveness.

Applicability: The suggested procedure can support environmental managers in updating their strategic planning of restoration measures and coordination with water quality management. The approach can be adapted and transferred to other countries and other management questions.

Lead partner organisation: Eawag, the Swiss Federal Institute of Aquatic Science and Technology, leads Case Study 7.

Cooperating partner: The Swiss Federal Office for the Environment is cooperating with AQUACROSS for Case Study 7: Biodiversity management for rivers of the Swiss Plateau. The Swiss Federal Office for the Environment is the Swiss federal government’s centre of environmental expertise and is part of the Federal Department of the Environment, Transport, Energy and Communication. It is responsible for ensuring the sustainable use of natural resources, minimizing natural hazards, reducing risks to the environment and human health from excessive pollution, conserving biodiversity and landscapes, and representing Switzerland in international environmental policy arenas.

FOEN and Case Study 7 are represented on the SPBTT by Dr. Yael Schindler Wildhaber.