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One-third of the world’s longest rivers remain free-flowing

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First ever global assessment of the location and extent of the planet’s remaining free-flowing rivers highlights severe degradation, and offers a method for tracking the status over time.Just over one-third (37per cent) of the world’s 246 longest rivers remain free-flowing, according to a new study published in the scientific journal Nature. Dams and reservoirs are drastically reducing the diverse benefits that healthy rivers provide to people and nature across the globe.

Among other findings in ‘Mapping the World’s Free-Flowing Rivers’, the researchers determined only 21 of the world’s 91 rivers longer than 1,000 km that originally flowed to the ocean still retain a direct connection from source to sea. The planet’s remaining free-flowing rivers are largely restricted to remote regions of the Arctic, the Amazon Basin, and the Congo Basin.

“The world’s rivers form an intricate network with vital links to land, groundwater, and the atmosphere,’’ said lead author Günther Grill of McGill’s Department of Geography. ‘’Free-flowing rivers are important for humans and the environment alike, yet economic development around the world is making them increasingly rare.”

Dams and reservoirs are the leading contributors to connectivity loss in global rivers. The study estimates, there are around 60,000 large dams worldwide, and more than 3,700 hydropower dams are currently planned or under construction.

“This first-ever map allows us to prioritize and protect the world’s remaining free-flowing rivers, as these are lifelines for wildlife and people across the globe,” said Michele Thieme, WWF Freshwater Scientist and co-author of the paper. “Rivers provide diverse benefits that are often overlooked and undervalued. Decision makers must consider the full value of rivers when they plan new infrastructure.”

Healthy rivers support freshwater fish stocks that improve food security for hundreds of millions of people, deliver sediment that keeps deltas above rising seas, mitigate the impact of extreme floods and droughts, prevent loss of infrastructure and fields to erosion, and support a wealth of biodiversity. Disrupting rivers’ connectivity often diminishes or even eliminates these critical ecosystem services.

Protecting remaining free-flowing rivers is also crucial to saving biodiversity in freshwater systems. WWF’s Living Planet Report 2018 recently revealed that populations of freshwater species have experienced the most pronounced decline of all vertebrates over the past half-century, falling on average 83 percent since 1970.

This week, IPBES’ 2019 Global Assessment Report on Biodiversity and Ecosystem Services highlighted threats to the world’s freshwater ecosystems and called for the protection and restoration of free-flowing rivers.

“While hydropower inevitably has a role to play in the renewable energy landscape, countries should also consider other renewable options,” said Thieme.

With the historic coming together of key decisions on environment, climate and sustainable development, 2020 provides an unmissable opportunity for world leaders to protect and restore free flowing rivers as part of a New Deal for Nature and People – an agreement which would aim to halt and reverse the loss of nature, and protect our planet.

The Living Planet Report, WWF’s flagship publication released every two years, is a comprehensive study of trends in global biodiversity and the health of the planet. The Living Planet Report 2018 is the twelfth edition of the report and provides the scientific evidence to what nature has been telling us repeatedly: unsustainable human activity is pushing the planet’s natural systems that support life on Earth to the edge.

Through multiple indicators including the Living Planet Index (LPI), provided by the Zoological Society of London (ZSL), the report shows us the urgent need for a new global deal for nature and people with clear, ambitious goals, targets and metrics, to reverse the devastating trend of biodiversity loss currently impacting the planet.


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Günther Grill
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