As the dams on the Hiitolanjoki in Finland came down, it began to change — the water quickened and cooled, sounding less like a reservoir and more like a river again. Then came the fish.
For the first time in more than a century, salmon pushed upstream past where three hydropower dams once stood, reclaiming a stretch of water that had been cut off for more than a century.
Similar transformations are unfolding across Europe, where countries are dismantling aging dams and weirs — barriers that once powered mills and factories but now often serve little purpose.
“Once you take a barrier out, the river takes over,” Angela Ortigara, senior adviser and freshwater strategist at WWF Netherlands, told CNN. “It’s one action that has an immediate effect and a long-term benefit.”
A record 603 barriers were removed across 21 countries in 2025 — the highest number ever recorded — according to the latest annual report by Dam Removal Europe, a coalition of six organizations working to restore river connectivity.
The removals helped reconnect more than 3,740 kilometers (2,324 miles) of rivers across the continent and are tied to the EU’s goal of restoring 25,000 kilometers (15,534 miles) of free-flowing rivers by 2030.
According to the report, released last week, the number of removed barriers surpassed the previous record set in 2024 by 11%.
Removals in 2025 were also six times higher than the first count conducted in 2020.
The numbers signal that river restoration is becoming more widely adopted but also reflect a broader reassessment of how rivers function in an era of climate extremes. What was once seen as progress is increasingly viewed as a growing environmental liability.
Fragmented rivers
An estimated 1.2 million barriers — including dams, weirs, culverts and sluices — fragment Europe’s rivers, according to the Adaptive Management of Barriers in European Rivers (AMBER) research project, one of the most comprehensive assessments of river connectivity ever conducted on the continent. Many of the structures were built decades ago for hydropower, navigation or agriculture, but thousands are now obsolete.
Scientists and environmental groups say the consequences can be far-reaching.
“When a river is dammed, its channel — once protected by riparian vegetation — is transformed into a pond or reservoir of still water exposed to the sun. This significantly increases water temperature,” said Pao Fernández-Garrido, senior grants manager for the European Open Rivers Programme, a Europe-wide funding initiative that supports the removal of small dams and river barriers to restore natural river ecosystems.
Large volumes of water in reservoirs can also be lost through evaporation. Organic material trapped in reservoirs accumulates and decomposes over time, releasing methane — a potent greenhouse gas that significantly contributes to global warming, Fernández-Garrido told CNN.
Fragmented ecosystems are also far less able to cope with increasing floods, droughts and climate extremes, according to the European Environment Agency. Over the past decade, nine out of 10 natural disasters on the continent were water-related, it said.
“We have lost around 80% of our wetlands over the last millennium through drainage, sealing and degradation,” the agency told CNN. “Wetlands help reduce these risks by acting like natural sponges, absorbing water during floods and releasing it slowly during droughts.”
Dam Removal Europe said river fragmentation is a major contributor to the decline of freshwater biodiversity in Europe, citing a recent European Commission assessment that found more than 42% of the continent’s freshwater fish species are threatened, while nearly two-thirds are considered at risk of becoming threatened or are already close to that status.
Species such as Atlantic salmon and European eel, along with some trout populations, can be blocked or delayed from reaching upstream habitats required for reproduction, contributing to population declines, or, in some cases, local extinction.
Even where fish passes are installed, their effectiveness varies, and they often fail to accommodate weaker-swimming species, leaving significant stretches of river ecosystems partially disconnected.
The impact extends beyond fish. River connectivity supports entire aquatic ecosystems, from insects to birds and mammals. When sediment flow is disrupted, riverbeds can be simplified and less suitable for spawning, while altered temperatures and flow reduce habitat diversity.
There are growing concerns, too, about Europe’s aging water infrastructure. Many obsolete barriers are not properly maintained and can become safety risks as they deteriorate, particularly during extreme weather events.
“Building river barriers brings a long list of safety and environmental problems,” said Fernández-Garrido. “It is always safer and more cost-effective to work with nature rather than against it.”
The growing momentum behind river restoration is now also being reinforced through the EU nature restoration policy.
However, the policy has also faced criticism from some farming groups and policymakers concerned about potential impacts on land use and rural livelihoods.
The EU’s Nature Restoration Regulation, which entered into force in 2024, sets binding targets to restore at least 20% of the EU’s land and sea areas by 2030, including restoring at least 25,000 km of rivers to a free-flowing state. It aims to restore nearly all ecosystems in need of restoration by 2050. The legislation marks the first time river connectivity and barrier removal have been embedded in EU law.
“This regulation has the potential to be a real game changer. It is not just about protecting what is left. It is about bringing nature back, about bringing our rivers back,” the European Environment Agency said.
Rivers restored
Removing a dam, however, is rarely as simple as tearing down concrete.
Projects can take years of environmental assessments, engineering studies and negotiations with dam owners and local authorities. Sediment must be carefully managed, riverbanks stabilized and ecosystems monitored after demolition.
But once barriers are removed, the transformation can happen remarkably fast.
In Finland, the removal of the three hydropower dams along the Hiitolanjoki River between 2021 and 2023 reopened migration routes for critically endangered landlocked salmon, restoring access to spawning grounds that had been blocked since the early 1900s. Salmon returned to parts of the river within the first migration season.
Farther east, attention is now turning to the Palokki hydropower dam in Finland’s Vuoksi river basin, where plans are underway to restore connectivity across another heavily fragmented watershed.
“When this project is implemented, it will be the biggest Open Rivers Program project ever supported,” Fernández-Garrido said. “This dam removal will open 1,523 kilometers (946 miles) of river.”
Elsewhere across Europe, similar restoration efforts are accelerating.
In France, the removal of the Vezins in 2020 and La Roche-Qui-Boit in 2022 dams on the Sélune River, which had been operating since the 1920s and 1930s, restored nearly 90 kilometers (56 miles) of free-flowing river in one of the largest dam removal projects ever undertaken in Europe.
In England’s Lake District, the dismantling of Bowston Weir in 2022 on the River Kent has helped restore more natural river flow, improving conditions for migratory fish and surrounding ecosystems.
In Belgium, culvert removals in the Anlier forest are reconnecting smaller tributaries that play an important role in local biodiversity.
Spain, Denmark, Sweden, Germany and Estonia have all undertaken barrier removal projects in recent years, though the scale of these efforts varies considerably between countries.
In 2025, Sweden removed the most barriers, 173, followed by Finland, 143, and Spain, 109.
Countries in southern and southeastern Europe, including Slovakia, Croatia, Bosnia and Herzegovina, Greece and even war-torn Ukraine, have also undertaken barrier removals in recent years, Ortigara pointed out.
In the United States, large dam removals have shown how quickly rivers can recover once barriers come down.
On California’s Klamath River, the largest dam removal project in US history was completed in 2024, reopening hundreds of miles of habitat for migratory fish. On Washington’s Elwha River, earlier dam removals restored sediment flow and triggered the return of fish and vegetation after more than a century of disruption. In Europe, many removals still involve much smaller structures — low weirs, culverts and aging hydropower barriers — but experts say their cumulative impact is growing.
“We have more than a million barriers in Europe,” Ortigara said. “Removing a few hundred each year is a start — but it’s not enough.”
Success, experts say, will depend on restoring entire river stretches and drainage basins, working closely with local communities and ensuring that once connectivity is restored, it is maintained over time. “The real challenge now is implementation — doing it at scale and in a strategic way,” the European Environment Agency said.
“When a river is alive, it has a sound,” Ortigara said. “You hear it trickling down the rocks. You see vegetation around it. It is this flow of life.”
Across Europe, that sound is now beginning to return.
Source: CNN
