Valuing and restoring saltmarshes in the Dutch Delta

A large part of the Netherlands lies below sea level where water finds its way to the sea via the many large rivers that flow through the country. This makes the Netherlands a typical delta region, making it an attractive place to live and therefore attracting many human activities. Due to the abundance of water and its low position, the Netherlands is prone to flooding. In the South-West Delta, three major rivers flow into the sea: the Rhine, the Maas and the Scheldt. The South-West Delta (Delta waters and Voordelta) contains at the same time natural values that are rare in Europe, has a high species diversity and provides a habitat for a large number of certain species.

The South-West Dutch Delta is important because of the value of the ecosystem services it provides to society, its vulnerability to fragmentation and loss, and its potential role in storing ‘blue carbon’. It is a large area of tidal wetlands with mudflats, islets, sand dunes and wet meadows. The wetlands play an important role in flood mitigation. Within the South-West Dutch Delta, the focus is on the Oosterschelde and the Westerschelde because of the special characteristics of these areas. Land use in the case study area is becoming increasingly complex.

This is due to the combination of many different functions: security, nature, fishing, recreation, agriculture and shipping. Functions that can be mutually reinforcing, but also in conflict. Coastal wetlands in north-west Europe have been identified as having major data gaps in terms of mapping and defining their habitats, their condition and the pressures on their biodiversity and ecological integrity, which are crucial for addressing land-sea governance issues. By focusing on coastal wetlands such as the South-West Dutch Delta and its catchment, the approach used in RESTORE4Cs allows for scaling up and generalisation to other types of freshwater wetlands, including floodplains and peatlands.

Three options have been discussed with stakeholders during a workshop in September 2024 and second through additional surveys in February 2025. The workshop in September was the first organised among the case pilots. It showed the need to further align with attendees on expectations related to the study and specific contributions from the case pilots. This provided a test-and-learn opportunity that proved helpful to refine workshop’s content for the other case pilots.

The options discussed are:

Option 1: “Business as Usual”: The region has a long, centuries old, tradition of building dykes (and dams since the 1960s) as flood prevention infrastructure for the people living on the various islands and peninsulas. Similarly, small dams have been constructed in front of salt marshes to protect these habitats against erosion. As a result, salt marshes would slowly but steadily disappear.

Option 2: Restoration of salt marshes with green engineering: Engineering could be turned green to give more room for natural hydrodynamics (erosion and sedimentation) to restore salt marshes, i.e. making semi-open holes in dykes reintroduces tides, flooding and salinity to damaged salt marshes. As a result, salt marshes would probably recover to a certain extent and expand their acreage.

Option 3: Restoration of salt marshes with civil engineering: The same engineering mentality as in constructing dykes and dams could also be used to restore salt marshes by replacing natural sedimentation with artificial sedimentation, i.e. sand/sediment suppletion. As a result, salt marshes disappearance could be slowed down.

Ensuring policy coherence and data continuity was recognized. There is a need for explicit information about the status of wetlands is essential for prioritising areas for their restoration, as requested under the Nature Restoration Regulation (NRR), and for developing well-defined restoration measures. There is a need for diversifying funding for restoring wetlands and to recognize the importance of social acceptability

© Photos and video-documentary by LifeWatch ERIC/ Università del Salento