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More than half of the world's rivers impacted by human activity

Friday, February 19th 2021, 4:56 pm - Humans have had a significant impact on the world's smaller waterways, according to a new study.

More than half of our planet's rivers have been heavily impacted by human activity, resulting in a loss of biodiversity, an increase in pollution, and non-native species proliferation, according to a new paper published in the journal Science.

Rivers and lakes don't take up much space, covering less than 1 per cent of Earth's surface, but they play a big role in maintaining a healthy ecosystem. According to the study's authors, small waterways support nearly a quarter of the planet's vertebrates species.

For the paper, Sébastien Brosse at Paul Sabatier University in Toulouse, France, and colleagues, began analyzing data from 2,456 river basins from around the world more than a decade ago. In total, the basins sustain more than 80 per cent of the world's freshwater fish.

Each basin was assigned a score between 0 and 12, with higher scores representing waterways heavily impacted by human activity, which includes overfishing and pollution from farming and other human activities.

Researchers found that 53 per cent of the basins studied had a score greater than 6, indicating fish biodiversity was severely impacted by humans.

High-income countries had the largest concentration of impacted lakes, and about 14 per cent of rivers in the study showed little impact.

“The less-impacted rivers are mainly located in Africa and Australia,” says Brosse told New Scientist, noting this was likely due to a slower industrialization rate in Africa and low population density around many of Australia's lakes.

UGC: Anglin Lake, Saskatchewan Submitted: Maurice garand File photo submitted to The Weather Network by Maurice Garand


Over the years there have been numerous studies pointing to the negative impact human activity has had on local waterways.

A 2019 paper focusing on 29 waterways in 10 European countries, for example, found every river and canal tested contained multiple pesticides.

The most polluted waterway was found in a Belgian canal and the pond was, at the time of data analysis, so saturated with veterinary antibiotics and chemicals that its water could likely be used as a pesticide, researchers from the University of Exeter said.

In it the canal they identified 38 different weed killers, 10 insecticides, 21 fungal killers, herbicides, and traces of veterinary medication.


When examining the impact on a lake, looks can be misleading. A 2017 study, for example, found that the clearest, bluest lakes are often the most polluted.

A 13-year analysis of more than 139 Iowa lakes found most of the lakes in the farming state are green because fertilizer runoff into waterways causes an abundance of algae.

Too much algae can cut off oxygen to organisms below, but it is naturally found in nature in smaller amounts.

Iowa's clearest lakes were found to have fertilizer levels that caused nutrients to rise to more than thirty times higher than normal, enough to kill off all the algae, similar to how using too much fertilizer can burn grass.

Based on the findings, the authors suggest regulators stop using water clarity as an indication of water health.


In Canada, 7,699 industrial facilities produce some 4.55 million tonnes of pollutants annually, covering more than 320 substances, according to the Government of Canada. From that, more than 150 billion litres of sewage is discharged into Canadian waters says Diane Orihel, an assistant professor at the School of Environmental Studies at Queen's University.

"Sometimes, pollution is blatantly obvious: the iridescent slick of an oil spill, goopy algae washing up on a beach or black smoke belching from a smokestack. But, more often than not, pollution is more inconspicuous," she writes.

"Our air, water, land, and wildlife are tainted with thousands of chemicals that we cannot see, smell, or touch. It may not come as a surprise then, that this unnoticed pollution isn’t considered the important threat to wildlife that it should be."

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