The largest tidal system in the world
The Wadden Sea is a tidal system that is underwater at high tide and largely exposed at low tide. The Wadden Sea is the largest contiguous area with exposed mudflats in the world and is also affected by climate change.There is a lot of information about climate change, habitats of plants and animals, and other ecological developments. “But all that data is scattered and difficult to compare. Researchers use different methods and present the results in different ways,” says Patrick Bogaart, researcher in natural capital and biodiversity at Statistics Netherlands (CBS): “Our job is to bring all those separate data together into one clear story.
The systematics boil down to combining the techniques behind the Living Planet Index with the development of indicators for ecosystem quality, as in our work on natural capital. Then you get a whole list of report cards. Put them together and you can create a final report: the State of the Wadden Sea. An integrated assessment of the state of the Wadden Sea as a whole.”
Collaboration partner
The Wadden Sea is one of the most studied natural areas in the world. An indispensable link in the life of migratory birds, fish, and seals. There is fishing, shipping, recreation, and research. The Wadden also form a natural protection of the northern coast of our country. In the Agenda for the Wadden Area 2050, from governments and involved parties, it is described: “sustainable protection and development as a natural area, maintaining the characteristic open landscape” for the Wadden Sea. To provide that protection, the Ministries of LVVN and IenW started in 2022 developing a Wadden Sea Nature Policy Framework focusing on reducing the negative impact of use.“Knowledge of the Wadden Sea was abundant,” says Rutger Bults, project leader of the Wadden Sea Nature Policy Framework at the Ministry of Agriculture, Fisheries, Food Security, Nature (LVVN). “What was missing was a complete picture. The Wadden Sea is a very special ecosystem in which everything is interconnected. We missed that interconnectedness in monitoring developments.” This led to a joint assignment from the ministry to the Wadden Academy to produce a State of the Wadden Sea. The Wadden Academy is the knowledge center for the Wadden area.
Katja Philippart, coastal ecologist and director of the Wadden Academy, embraced the assignment immediately. “It was a long-cherished ideal and a first attempt was made in 2014 (Wadden monitoring in the Spotlight). This also immediately linked policy and management: the science-policy matrix.” That 2014 pilot made clear it would not be a simple project. The goal was a report that not only describes the current state of the area but also shows how it develops over time. The wish list was long, there were many data and information sources of various magnitudes and units. CBS was naturally an important collaboration partner.”
238 indicators
How do you make one clear overview from all those separate data and different interests? What does it mean when statistics and ecology work so closely together?
The State of the Wadden Sea 2025 provides a broad and clear picture of how the Wadden Sea is doing as a natural area. It helps policymakers make decisions based on facts and figures.
The report contains an assessment based on 238 indicators divided into three themes: weather & climate, habitat, and species. These indicators show how things are now (current state) and how they have changed over the past 12 years (trend):
• 38% of the indicators score worse than the reference values and some continue to deteriorate.
• 28% of the indicators provide an uncertain picture compared to the reference values.
• 32% score better than the reference values.
Increasing knowledge
“This report is an important building block for the new Wadden Sea Nature Policy Framework that we are developing together with the Ministry of IenW,” says Bults. “It is important that we have found each other in the goals and criteria for this report. We as the Ministries of LVVN and IenW have different roles in the area, but a healthy and resilient Wadden Sea is in the interest of us all. The State of the Wadden Sea provides a lot of information to verify many assumptions, and that is a big gain. We do not know everything yet, but enough to take the next step in protecting the Wadden Sea.Philippart adds: “I am very happy with the result. And also with the insight that we actually still do not have a good picture of some aspects of the Wadden Sea. Specific fauna, such as zooplankton, for example. But also spatial aspects. It does matter whether you are in the eastern Wadden area or in the west. We have largely not yet looked at those differences separately.”
Patrick Bogaart also sees opportunities there. “We are in talks with our German and Danish colleagues. Within Europe, new guidelines are being developed for habitat quality. The State is actually already a forerunner here. The joint aim is to harmonize as much as possible.”