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Home Science Humans have severely affected fish biodiversity in half of all rivers 

Humans have severely affected fish biodiversity in half of all rivers 

The Mississippi River near Brainerd, Minnesota

The Mississippi river close to Brainerd, Minnesota

Daniel Thornberg/Alamy

Fish biodiversity in freshwater methods, resembling lakes and rivers, has been declining because the starting of the economic revolution – a lot in order that researchers now estimate human exercise has severely affected the fish biodiversity in greater than half of the world’s rivers.

Our planet’s rivers and lakes present a habitat for almost 18,000 fish species, regardless of masking lower than 1 per cent of Earth’s floor. Sébastien Brosse at Paul Sabatier University in Toulouse, France, and his colleagues have been gathering knowledge from 2456 river basins the world over for greater than a decade.

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These basins host over 14,000 fish species, which is greater than 80 per cent of the worldwide freshwater fish pool.

Brosse and his staff created an index to measure the modifications in fish biodiversity in these rivers and the way they have been affected by human exercise. Previous measures of biodiversity usually solely assessed the quantity of totally different species in a specific ecosystem. This new index additionally measures the perform of every freshwater species and their evolutionary relationships.

Using these measures, every river basin was given a rating between 0 and 12 – the upper the rating, the upper the change in biodiversity because of this of human exercise.

The staff discovered that 53 per cent of the river basins had a rating greater than 6, which means their fish biodiversity had been severely affected by human actions, particularly after the economic revolution. Unsurprisingly, these had been situated principally in high-income nations, resembling western Europe and North America, the place people have closely manipulated rivers.

Just 14 per cent of river basins in the research have been little affected by human exercise, however these solely present a habitat for one-fifth of the world’s freshwater fish species.

“The less-impacted rivers are mainly located in Africa and Australia,” says Brosse. This might be on account of a slower price of industrialisation in Africa and low inhabitants density round rivers in Australia, he says.

“Rivers which have the most economic development around them, like the Mississippi river, are the most strongly impacted,” says Brosse. Along with overfishing and local weather change, dams are particularly dangerous for freshwater biodiversity as they cut back the stream of vitamins and block migrating fish.

Sustaining fish biodiversity is vital for a lot of communities who eat quite a bit of fish, says Richard York on the University of Oregon. “For example, in Cambodia, more than 60 per cent of the protein in diets is supported by freshwater fish,” says Brosse.

Journal reference: Science, DOI: 10.1126/science.abd3369

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