The fragmentation of rivers has resulted in a significant deterioration of biodiversity, water quality and natural habitats.
It is widely held that rivers support some of the Earth’s richest biodiversity and provide essential ecosystem services to society. Free flowing “open rivers” provide habitat for many species of plants and animals that depend on flowing water, deliver sediment that keeps deltas above rising seas, and provide nutrients to fertilise floodplains and create wetlands. However, when rivers become fragmented their ecological status rapidly deteriorates. European rivers are the most fragmented in the world and only one third of its rivers have ‘good ecological status’, as defined by the EU Water Framework Directive.
One of the biggest causes of river fragmentation is the presence of man-made barriers to river flow. In 2020, the EU-funded AMBER project estimated that there are in excess of one million barriers in rivers and streams across Europe, amounting to 0.74 barriers / km. This is having a catastrophic impact on biodiversity. The change in flow caused by dams can fundamentally impact habitats, potentially over thousands of miles. The main negative impacts of dams include: