Fish Populations In 86% Of Rivers Worldwide Have Been "Seriously Damaged"; Europe, N. America Worst
Rivers in which fish populations have escaped serious damage from human activities make up just 14% of the world’s river basin area, according to the most comprehensive study to date. Scientists found that the biodiversity of more than half of rivers had been profoundly affected, with big fish such as sturgeon replaced by invasive species such as catfish and Asian carp. Pollution, dams, overfishing, farm irrigation and rising temperatures due to the climate crisis are also to blame.
The worst-hit regions are western Europe and North America, where large and affluent populations mean humans’ impact on rivers is highest, such as with the Thames in the UK and the Mississippi in the US. Rivers and lakes are vital ecosystems. They cover less than 1% of the planet’s surface, but their 17,000 fish species represent a quarter of all vertebrates, as well as providing food for many millions of people. Healthy rivers are also needed to supply clean water.
Other recent research has shown that global populations of migratory river fish have plunged by a “catastrophic” 76% since 1970, with a 93% fall in Europe. Large river animals have fared worst, with some like the Mekong giant catfish on the verge of extinction. A 2019 analysis found only a third of the world’s great rivers remained free flowing, due to the impact of dams.
Sébastien Brosse, at Université Paul Sabatier in Toulouse, France, who led the new research, said rivers in many rich nations were unrecognisable compared with how they were before the industrial revolution. “Then we had sturgeon that were more than 2 metres in size, we had thousands of salmon, and many other fish that have almost disappeared today.” “The River Thames is one of the most impacted – it scored the maximum 12 out of 12 in our study,” he said. “There has been an increase in water quality in western European and North American rivers in recent decades, but I’m not sure the speed of change is sufficient because there has been a really steep decline in fish populations.”
EDIT
https://www.theguardian.com/environment/2021/feb/18/very-few-of-worlds-rivers-undamaged-by-humanity-study-finds
