River wildlife moves freely once dams are removed – but so too can invasive species

Weirs and dams act as barriers within river ecosystems – removing them affects how aquatic wildlife and invasive species move. Bardhok Ndoji/Shutterstock

Almost a quarter of all freshwater species are threatened with extinction. The removal of human-made barriers from rivers, such as dams and weirs, is a popular way to restore water flow and sediment transport to its natural state and allow fish and other aquatic wildlife to move more freely.

There are more than 1.2 million barriers in European rivers. But more than 2,200 dams, weirs and other barriers have been removed between 2020 and 2025.