Conservationists have mapped out more than 70,000 weirs, dams and other river barriers across the UK, warning that they are a “huge problem” for wildlife and pollution.

A new database compiled by environmental charity WildFish reveals there is an average of one manmade barrier for every 2.5km (1.5 miles) of waterway across 150,000km (93,000 miles) of rivers across Britain.

Many of these weirs, concrete dams, underwater gates and other barriers are “old, redundant” installations that serve no practical purpose, the charity says.