Freshwater ecosystems are exposed to a wide range of stressors that affect every level of these complex environments. Human-induced habitat changes also have profound impacts on parasite communities, triggering far-reaching ecological cascades. A team of biologists from the University of Duisburg-Essen has highlighted the effects of five types of habitat alteration on parasite communities and the consequences that follow. Their findings were published in Parasitology Research and aim to draw attention to the need for integrative ecosystem management strategies.

Habitat degradation, agriculture, dams, urbanization, and even the restoration of degraded freshwater ecosystems all represent major interventions in freshwater environments. These changes affect both parasites and their hosts, often with significant ecological and public health consequences that are rarely considered in a comprehensive way.

The team, led by first author Bernd Sures, has now published the first comprehensive review of such cases, shedding light on the role of parasites in ecosystem change. The review shows that parasites are themselves victims of biodiversity loss caused by habitat degradation, while under other circumstances they may pose a potential public health risk. For example, artificial lentic waters created by dams and reservoirs can promote outbreaks of certain parasites because they provide ideal conditions for specific hosts and parasites, including those responsible for diseases such as malaria.

In the restoration of freshwater ecosystems such as the Emscher River, whose recovery has been accompanied by several research projects at the University of Duisburg-Essen, parasite communities also recover to some extent. However, because many environmental stressors persist, recovery is often dominated by generalist parasites with short life cycles, resulting in altered parasite community composition and incomplete ecological recovery. Similar impoverishment of parasite communities can also be observed in intensively farmed landscapes, where agricultural chemicals disrupt complex parasite life cycles and eliminate hosts, while irrigation and eutrophication create new reservoirs that favor certain parasite species.

This review demonstrates the multiple roles that parasites play in freshwater ecosystems: they are integral components of these systems, valuable bioindicators, beneficiaries as well as victims of habitat change, and important disease agents. The authors conclude that integrative approaches to both ecosystem restoration and public health should consistently take parasites into account—not only as components of ecosystems but also as potential vectors of disease.

The study was conducted within the Collaborative Research Centre RESIST, funded by the German Research Foundation (DFG) and coordinated at the University of Duisburg-Essen.

Original publication: doi.org/10.1007/s00436-026-08730-1

Image caption: Straightened and restored sections of the Emscher River, with the urban landscape of Germany's Ruhr region visible in the background.