17.07.2025 | Lisa Bose | WSL News
The loss of common species can destabilise food webs, with far-reaching consequences for entire ecosystems and their services. This is shown by a new study by the Swiss Federal Institute for Forest, Snow and Landscape Research WSL and ETH Zurich, published in the Nature journal Communications Biology. This has far-reaching consequences, especially when wetland species are involved.
- Common species are crucial for the stability of food webs. Their disappearance triggers a particularly large number of secondary losses.
- Species from wetlands account for only around 30 per cent of all recorded species. However, they are responsible for almost 70 per cent of all connections in Switzerland's food webs. Their loss leads to the collapse of the webs much more quickly than when other species become extinct.
- Biodiversity protection must be thought of in broader terms – across species and habitat boundaries.
Eating and being eaten – all living beings in an ecosystem are interconnected and interdependent. This can be illustrated in a food web. But what happens when a species disappears from such a web because it becomes extinct?
An international team of researchers led by WSL and ETH Zurich has modelled the effects of various extinction scenarios on regional food webs in Switzerland for the first time. To do this, the researchers created a "metaweb" – a complex network with over 280,000 predator-prey relationships between around 7,800 species of plants, vertebrates and invertebrates. Based on this data, the researchers then simulated the loss of species from different habitat types.
The result: if common species disappear from key habitats such as wetlands or agricultural land, regional food webs collapse fairly quickly. Among other things, this means that ecosystem services such as pollination are no longer guaranteed.
Keeping an eye on common species ¶
The impact was particularly significant when wetland species were absent. "Although wetland areas in Switzerland are relatively small and these species are not numerous, their extinction led to significant changes in the food web," says Merin Reji Chacko, WSL researcher and lead author of the study. One explanation for this is that wetland species more often move between habitats, contributing to the functioning of ecosystems in different places – for example, dragonflies, which live in water as larvae and on land as adults.
Other studies have shown that even small alpine wetlands can harbour very species-rich plant communities. Since plants form the basis of the food chain, this can lead to an increase in biodiversity in the communities that depend on these plants.
Another important finding is that it is not the rare species but the common ones that have the greatest influence on the stability of regional food webs. If common species are deliberately removed, they also cause the demise of other species that depend on them – similar to a domino effect. They act as a kind of "hub" in a network, as they have many connections to other organisms and often occur in different habitats.
Looking beyond system boundaries ¶
For practical nature conservation, this means that protective measures should not only focus on rare species, but also increasingly on species that are (still) common and play key roles in ecosystems. However, this does not mean that rarer species can be neglected in nature conservation. "Common species are widespread so regionally they become very important. But only a few species are common; most are rare. Locally, it is the many rare species form a safety net that comes into play when one of the more common species disappears," explains Reji Chacko.
Equally important is the preservation of a mosaic of diverse habitat types that coexist side by side. Many species use multiple habitats and transport energy and nutrients between them.
"Our results show that the loss of species in one habitat can have far-reaching effects on organisms in neighbouring habitats within the same system – even over large distances, as these species can connect different habitats via the food web," explains Reji Chacko. "This means that conservation strategies must be developed across species and habitat boundaries in order to preserve biodiversity in the long term."
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