The removal of dams in Europe is reviving rivers and boosting biodiversity. Here’s how

• A record number of dams and other obstructions were removed from Europe’s rivers in 2022.Restoring free-flowing rivers enhances biodiversity and allows endangered fish to breed.The World Economic Forum’s Global Risks Report 2023 ranked biodiversity loss and ecosystem loss in the top five threats to life on Earth over the next decade.

A record number of dams and weirs were removed from Europe’s rivers in 2022, helping to restore the health of the continent’s freshwater arteries.The annual report from Dam Removal Europe (DRE), an alliance of seven wildlife and environmental organizations, shows that 325 obstacles were taken down across rivers in 16 countries, improving river flows and enabling fish to reach their breeding areas.

Restoring free-flowing rivers is an important way of increasing biodiversity, the report adds. The World Economic Forum’s Global Risks Report 2023 ranked biodiversity loss and ecosystem collapse as one of the top five threats to the world over the next decade.

One of the most unexpected dam removals took place in Ukraine, where the Ukrainian branch of the World Wide Fund for Nature (WWF) removed the 120-year-old Bayurivka Dam on the Perkalaba River in the Carpathian Mountains – despite the country being at war.Originally built to aid the transport of timber, the dam lay unused for 40 years and was at risk of collapse. Removing it reopened 27 kilometres of river, allowing fish, including the endangered Danube salmon, to reach their traditional spawning grounds.It is hoped the return of fish populations will boost the numbers of fish-eating animals in the area, such as brown bear, otter and European mink, creating what DRE says could become a “biodiversity hotspot” in the Carpathians.

Almost one-sixth of the obstacles to free-flowing rivers came down because they were obsolete and in danger of collapsing. These included ten hydropower dams up to a century old which had fallen into disrepair.

A Norwegian sports fishing club had campaigned to remove a 106-year-old hydropower dam on the Tromsa River, which was dynamited in January 2022. It’s been replaced by a step-pool cascade to allow fish to swim upriver again.In June 2022, the hydroelectric dam at La Rochequi-boit on the Sélune River in Normandy was removed, restoring 60km of the river. Meanwhile in Finland, the removal of the Lahnasenkoski Dam brought the country’s largest river restoration project a step closer to completion.In all, DRE says at least 832km of rivers were reconnected in a year which also saw progress towards new legal protections for rivers at both European Union and national government levels.Although hydropower is the world’s largest single source of low-carbon energy, supplying one-sixth of global electricity generation, DRE says more research is needed to quantify the cost of removing them when they reach the end of their operational lives.Europe has 150,000 obsolete dams and a recent study of dam removal in the US suggests that the average cost of removing a 10-metre-high dam is $6.2 million. DRE has welcomed a new app which calculates the exact cost of demolishing individual dams.