New Study in Nature: Just One-Third of the World’s Longest Rivers Remain Free-Flowing | WWF India

New Study in Nature: Just One-Third of the World’s Longest Rivers Remain Free-Flowing

Posted on 09 May 2019   |  
The Ganga is one of the rivers in which the Ganges shark is found.
© Anil Cherukupalli/WWF-India
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 of free-flowing rivers over time
 
  • Only 37% of the world’s longest rivers remain free-flowing
  • Nearly 60,000 large dams exist worldwide, with more than 3,700 currently planned or under construction
  • Climate change is a growing threat to river health worldwide, both from direct impacts and as countries increasingly turn to hydropower as a renewable energy option
  • Indian rivers are exposed to sustained pressure from fragmentation and loss of river connectivity, constraining their capacity to flow unimpeded, affecting many fundamental processes and functions characteristic of healthy rivers and leading to the rapid decline of biodiversity and essential ecosystem services
  • A total 409,245 km of rivers was analyzed in India
 
  • Out of this, the length of short rivers (10-100 km) is 2,69,375 kms, medium length (100-500 km) is 95,638 kms, long rivers (500-1000 km) is 22,437 kms while under the very long category (>1000 km) the total length of rivers is 21,795 kms
  • Among the identified free flowing rivers in India a majority (96%) falls in the ‘short rivers’ category (10-100 KM)
Just over one-third (37%) 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.

A team of 34 international researchers from McGill University, WWF, and other institutions[i] assessed the connectivity status of 12 million kilometers (~7.5 million miles) of rivers worldwide, providing the first ever global assessment of the location and extent of the planet’s remaining free-flowing rivers.[ii]

Among other findings, the researchers determined that only 21 of the world's 91 rivers longer than 1,000 km (~600 miles) 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. Using satellite imagery and other data, our study examines the extent of these rivers in more detail than ever before.”

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. They are often planned and built at the individual project level, making it difficult to assess their real impacts across an entire basin or region.

“Rivers are the lifeblood of our planet,” said Michele Thieme, lead freshwater scientist at WWF and global leader of WWF’s free-flowing rivers initiative. “They provide diverse benefits that are often overlooked and undervalued. This first-ever map of the world’s remaining free-flowing rivers will help decision makers prioritize and protect the full value rivers give to people and nature.”

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 river connectivity often diminishes or even eliminates these critical ecosystem services.

Protecting remaining free-flowing rivers is also crucial to saving biodiversity in freshwater systems. A recent analysis of 16,704 populations of wildlife globally showed that populations of freshwater species experienced the most pronounced decline of all vertebrates over the past half-century, falling on average 83 percent since 1970.
‘This global study has given the much-required insight and methodology to identify free flowing rivers in our country, and to work with diverse stakeholders for developing a roadmap for the protection of such intact river systems in India. The study highlights the relevance of free-flowing rivers and the potential they hold to increase the resilience of aquatic and riparian ecosystems for the benefit of millions of people,” added Ravi Singh, Secretary General & CEO, WWF – India.

The study also notes that climate change will further threaten the health of rivers worldwide. Rising temperatures are already impacting flow patterns, water quality, and biodiversity. Meanwhile, as countries around the world shift to low-carbon economies, hydropower planning and development is accelerating, adding urgency to the need to develop energy systems that minimize overall environmental and social impact.

“Renewable energy is like a recipe – you have to find the right mix of ingredients to have both a sustainable energy grid and a thriving natural world,” said Thieme. “While hydropower inevitably has a role to play in the renewable energy landscape, well-planned wind and solar energy can be more viable options for rivers and the communities, cities, and biodiversity that rely on them.”

The international community is committed to protect and restore rivers under Agenda 2030 for Sustainable Development, which requires countries to track the extent and condition of water-related ecosystems. This study delivers methods and data necessary for countries to maintain and restore free-flowing rivers around the world.
Visit freeflowingrivers.org for more information on free-flowing rivers and an interactive map of the world's rivers.
 
[i] Contributing Institutions:
McGill University, WWF-US, WWF-NL, WWF-UK, WWF-Mediterranean, WWF-India, University of Basel, Joint Research Centre (JRC), WWF-China, WWF-Canada, WWF-Zambia, WWF Greater Mekong Programme, The Nature Conservancy, University of Nevada, WWF-Malaysia, IHE Delft, WWF- Germany and HTWG Konstanz, King’s College London, Umeå University, Swedish University of Agricultural Sciences, University of Washington, Harvard University, University of Wisconsin-Madison, Conservation International , WWF-Mexico, WWF International, Stanford University, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Freie Universität Berlin, WWF-Brazil, Eberhard Karls University of Tübingen.
 
[ii] First ever science-based definition of a free-flowing river:
Rivers where ecosystem functions and services are largely unaffected by changes to fluvial connectivity allowing an unobstructed exchange of water, material, species, and energy within the river system and with surrounding landscapes.
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For more information, please contact:
Ms. Rituparna, rsengupta@wwfindia.net I 9810514487
Mr. Suresh Babu suresh@wwfindia.net I 9818997999
The Ganga is one of the rivers in which the Ganges shark is found.
© Anil Cherukupalli/WWF-India Enlarge

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