Humans have damaged 86 per cent of the world's rivers. Researchers looked at data on over 2,500 rivers, but none in the Arctic and Antarctica or in deserts. The scientists looked at biodiversity changes over the past 200 years. Humans have seriously damaged biodiversity in over half of rivers. There are many reasons for this. One reason is new species of fish that are in rivers. Other reasons include pollution, dams and climate change.
The worst-hit rivers are in the big cities of Europe and America. The lead researcher said rivers which have the most economic development near them, like the Mississippi River or River Thames, are the most strongly impacted. The least-impacted are in Africa and Australia. This is because of fewer factories in Africa and smaller populations around rivers in Australia. He said rivers in rich nations are totally different to how they were 200 years ago.