A recent research shows that 86% of the world’s rivers have been damaged by human activities. The research     1     (conduct) by experts from a university in Toulouse, France,     2     examined data on over 2,500 rivers around the world.     3     (look) into changes in biodiversity (多样性) over the past 200 years, the scientists discovered that biodiversity in over half of the rivers has been seriously damaged by humans. The researchers said there were many reasons     4     this damage. A big reason is the     5     (introduce) of new species of fish into rivers. Other reasons include pollution, dams, overfishing, farming     6     climate change.

Unsurprisingly, the worst-hit rivers are in western Europe and North America. This is because these regions have large and rich     7     (city) crowded with people. The lead researcher Brosse said: “Rivers which have the most economic development around them, like the Mississippi River, are the most     8     (strong) affected.” The River Thames in London was one of the worst-affected rivers in the study. The least-affected rivers are in Africa and Australia. This is probably due to a     9     (slow) rate of industrialization in Africa and smaller population around rivers in Australia. Brosse added that rivers in many rich nations are unrecognizable compared with how they     10     (be) 200 years ago.