Biodiversity has a soundtrack. We all hear birdsong, even in a concrete jungle, but when a landscape is truly thriving, layers of sound emerge: from the flutter of wings to the splash of a tail darting through the water.
Oswin van der Scheer is listening closely at the Burkmeer site in Amsterdam, the pilot location of Palus Demos in The Netherlands. This demonstration site is being used to research cattail (typha) as a bio-based insulation material for the construction sector. At the 50-hectare Burkmeer site, the water table has been raised. Cattail is growing there, although not yet everywhere with equal success. In some parts of the 50 hectares, nothing grows at all, while in other sections the crop is thriving. The reasons behind these differences still need to be analysed.
Oswin is a researcher from the Faculty of Science Institute for Biodiversity and Ecosystem Dynamics – University of Amsterdam, and a member of Palus Demos, a Horizon Europe project researching paludiculture (farming on wet or rewetted peatlands) at three strategic sites in Europe.
Paludiculture has the potential to reduce greenhouse gas emissions and land subsidence. Rewetting the area is seen as a promising solution. In addition, it is expected that the water in the polder will have a purifying effect on the surrounding waterways, which are crucial for biodiversity.
Oswin has placed microphones across the entire site, both above ground and underwater, to listen to the changing ecosystem. Rewetted peatlands naturally attract different wildlife species, such as reed warblers, crested newts, water spiders and herons. The question is whether cultivating cattail as a commercial crop also has a positive effect on biodiversity.
“We have installed microphones and hydrophones at three neighbouring sites for comparison: in a drained peat meadow, at our paludiculture site, and at a fully restored, near-natural peatland,” Oswin explains. “Every ten minutes, one minute is recorded, day and night.”
“Animals make many different sounds: calls to establish territory and find one another, but also the flapping of wings, foraging invertebrates, and frogs and lizards moving through the water. There is a relationship between the health of an ecosystem and the complexity of its soundscape. That creates very interesting data.
“What we are investigating is: where does the paludiculture site stand in terms of biodiversity between a drained meadow and a natural peatland? Is it closer to drained land or to a natural ecosystem?”
Oswin is collaborating with the Theoretical and Computational Ecology Group at the University of Amsterdam to collect and process the data. It is not the first time this method has been used to monitor biodiversity levels, but within the context of peatlands — and paludiculture in particular — it is still a relatively new approach. A recent report by the RSPB and the University of Cambridge suggests that wet farming sites can support three times more birds than drained agricultural grasslands.
The data collected by Oswin at the Palus Demos site records all sounds present at the location: from insects and invertebrates to birds and beyond.
“It is an interesting way of looking at biodiversity. We are examining the ecosystem as a whole. Usually, researchers focus on specific species, such as birds or amphibians. This is a whole-system approach. The idea of complexity is not new in ecology, but it is innovative within peatland restoration.
“We are using new methods that may also be useful for other researchers. This is a low-impact measurement method and potentially also a low-effort approach for farmers and landowners. With just a few microphones, you can establish a baseline and monitor changes over time. It will never replace traditional ecological expertise, but it can support biodiversity monitoring and help identify trends.
“The data is now coming in, and the next step is to process and analyse it. We will continue recording for an entire year to include seasonal variations. From geese and ducks to toads, frogs and salamanders — we will be listening carefully to them all.
“And of course, we are curious to discover what added value this may bring to the results of the project itself. Perhaps it could even create an alternative source of income through agri-environmental management schemes, for example.“