( Find out more about how hydropower works here.)Īlthough most of the larger hydropower plants in Europe were constructed in the aftermath of World War II, much of Europe’s river fragmentation can be traced back centuries. With about 7,000 large dams, Europe generates 13 percent of its electricity from hydropower. “Smaller barriers, because there are so many of them, may in fact be more harmful,” says Carlos Garcia de Leaniz, a professor of aquatic biosciences at Swansea University in Wales and project coordinator of AMBER, the European Union Horizon 2020 program providing the first pan-European assessment of river fragmentation.Īt the same time, he says, there is some good news: “Mitigation efforts to improve river connectivity may not be as complicated as some had feared, since many of these smaller barriers are obsolete and could be easily taken out.” Boots on the ground While large storage dams can change how an entire river behaves, almost all barriers, no matter how small, have some effect on river life. These shorter barriers, most under two meters (6.5 feet) in height, are often overlooked even though their cumulative impact on river connectivity may be substantial. However, researchers found that at least 85 percent of barriers on European rivers are actually smaller structures such as weirs, culverts, fords, sluices, and ramps. Thousands of large dams across Europe were catalogued in the study, which is published this week in Nature. They stop the natural flow of sediments and prevent migratory fishes from travelling up or downstream to complete their lifecycles. ![]() “The numbers we found are higher than expected, and show that European rivers are broken,” says Barbara Belletti, a river geomorphologist who led the study at the Polytechnic University of Milan.Īrtificial barriers, like dams, are one of the biggest threats to river ecosystems. That’s more than one barrier for every mile of river (or 0.74 barriers per kilometer). In a four-year study spanning 36 European countries, scientists surveyed almost 1,700 miles of river by foot-and found at least 1.2 million obstacles preventing European rivers from flowing freely. Rivers in Europe are more fragmented-meaning their natural flows are interrupted by man-made barriers-than any other continent’s rivers, new research shows.
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