A study shows that humans have damaged 86 per cent of the world's rivers. The study is from a university in France. Researchers examined data on over 2,500 of the world's rivers. They did not look at rivers in the Arctic and Antarctica or in deserts. The scientists looked at changes to biodiversity over the past 200 years. Biodiversity in over half of rivers has been seriously damaged by humans. There are many reasons for this damage. A big reason is the new species of fish are in rivers. Other reasons include pollution, dams, overfishing, farming and climate change.

The worst-hit rivers are in western Europe and North America. These regions have big, rich towns and cities. The lead researcher said: "Rivers which have the most economic development around them, like the Mississippi River, are the most strongly impacted." London's River Thames is one of the worst-affected in the study. The least-impacted rivers are in Africa and Australia. The researcher said this is because of less industrialisation in Africa and low populations around rivers in Australia. He said rivers in rich nations are completely different to how they were 200 years ago.