More than half of world’s rivers heavily impacted by humans, study says

More than half of the world’s rivers have seen “marked biodiversity change” since the start of the industrial era, a new study finds.

Earth’s rivers and lakes cover just one per cent of the Earth’s surface but provide a home to a quarter of vertebrate species.

But human activities such as overfishing, damming and water pollution are having a profound impact on the world’s freshwater ecosystems.

The research uses a new index with the aim of quantifying this impact on a global level. It investigates the impact that humans have had on more than 2,400 river basins covering almost all of the Earth’s continental surface.

The findings show that 53 per cent of Earth’s rivers score highly for biodiversity change – “revealing deep and spatially distributed anthropogenic [human] impacts on fish biodiversity”, the authors write in their paper published in the journal Science.

Dr Guohuan Su, lead author of the study and fish ecologist at the University of Toulouse in France, told The Independent: “We developed a novel index, which allows us to combine multiple facets of change in diversity measurements together and provide a holistic view of the biodiversity changes.

“By using this index, we revealed that more than 50 per cent of the world’s river fish experienced marked biodiversity change since the beginning of the industrial revolution.”

The index combines six different measures of freshwater fish biodiversity. These include measures of species richness and species “dissimilarity” – a metric that allows scientists to study whether river ecosystems are becoming more homogenous as a result of human activity.

Scientists used the index to give each river basin a score between one and 12, with a score of six or higher indicating marked biodiversity change.

The map below shows the results for different river basins across the world. On the map, the colours orange to dark red are used to indicate basins that have seen marked biodiversity change since the start of the industrial era.

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The map indicates that river basins in western Europe, including the UK, have seen high levels of fish biodiversity change since the start of the industrial era. Parts of North America and Australia have also seen large shifts to fish biodiversity.

The study also finds that, in general, the world’s river ecosystems have become more homogenous as a result of human activity since the start of the industrial era.

Overall, the findings suggest that broad and widespread conservation measures will be needed to protect river ecosystems from human impacts, says Dr Su.

“Biodiversity conservation strategies should consider the cumulative and synergistic effects of multiple human activities on biodiversity,” he said.

“Many endangered fish species inhabit rivers heavily impacted by humans.”