Investigating the impact of nature restoration on greenhouse gases

Large tidal and salt marsh areas along the Scheldt have been lost due to land reclamation. Some parts of them are now being restored as part of the Flemish Sigma Plan and the Dutch Western Scheldt Nature Package.

The largest nature restoration project is in the 465-hectare Hedwige-Prosper polder. High and low tides once again occur in the former polders, allowing the tidal and salt marsh nature to slowly recover.

A carbon measuring station has now been installed in this area. This new station is part of the WETCOAST project, in which the University of Antwerp, KU Leuven and Vrije Universiteit Brussel are investigating the role of tidal areas in climate regulation.

Project coordinator Stijn Temmerman (University of Antwerp, Global Change Ecology Centre): “This new area offers a unique opportunity for knowledge development, because major questions remain: how quickly do the natural processes that are essential for the absorption of greenhouse gases and carbon sequestration recover? And how can we measure this accurately and on a large scale?"

The new measuring station should provide answers to these questions. The 6-meter-high construction contains sensors that permanently measure the exchange of carbon dioxide (CO2) and methane (CH4). Environmental factors such as wind, temperature, precipitation, light intensity and tide are also accurately measured. The entire installation is powered by solar energy.

The large amount of data is automatically forwarded to the UAntwerp campus for analysis. The design and installation of the measuring station's supporting structure was supervised by Jan De Nul, the dredging company that also contributed to the nature development of the area studied.

Stijn Temmerman: "WETCOAST is intended to find out how much carbon can be absorbed and stored in restored tidal areas. Salt marshes in our climate and mangrove forests in the tropics are among the most efficient ecosystems in the world for storing carbon and reducing global warming".

"But that function has been lost for many tidal areas because they were drained for human land use such as agriculture. Recently, salt marshes and mangroves are being restored. In addition to flood prevention and improving water quality and biodiversity, carbon storage is often cited as a motivation for their restoration. But how quickly is that carbon stored? That is an important question."

The research includes both manual measurements in the field, which take place under challenging conditions, and continuous measurements by advanced instruments. In addition, a drone is also used to monitor the development of the area.

Stijn Temmerman: "By bringing all these data together, we develop efficient methods to accurately map carbon storage in tidal areas. Within WETCOAST, we want to integrate these data into a new computer model with which we can calculate the future and current carbon storage in these tidal marsh areas, and therefore their contribution to climate regulation, much more accurately."

For the flux tower, WETCOAST builds on the expertise of the University of Antwerp with similar measuring set-ups. In the context of ICOS, a European research infrastructure for monitoring greenhouse gases, the University of Antwerp already manages 4 similar measuring stations in heathland, forest and arable land.

WETCOAST not only studies salt marshes but also mangroves, the tropical counterparts of our salt marshes. That is why parallel research is being conducted in the AquaForest project. Jan De Nul has constructed a new mangrove island in the Guayas Delta in Ecuador. The project serves as a blueprint for mangrove restoration worldwide. For the researchers, AquaForest offers a unique opportunity to compare carbon sequestration in both temperate and tropical tidal areas.

Vicky Stratigaki, project engineer at Jan De Nul: “We are convinced that restoring natural areas is a relevant response to climate change. Both mangrove forests and mudflats and salt marshes provide various ecosystem services. That is why we are happy to invest in research that maps the impact of nature restoration projects in detail. The fact that we can also do this worldwide in collaboration with WETCOAST will only increase the impact.”