Rivers of the world least at risk are those where human populations are smallest. Rivers in arctic regions and inaccessible areas of the tropics appear to be in the best health.
Tees Barrage, River Tees, Stockton, England (Photo by Ian Britton courtesy Freefoto.com)
This research is the first to assess both human water security and biodiversity in parallel and is the first to simultaneously account for the effects of pollution, dam building, agricultural runoff, the conversion of wetlands and the introduction of exotic species on the health of the world's rivers.
The report by an international team co-led by Charles Vorosmarty of the City University of New York, an expert on global water resources, and Peter McIntyre, an expert on freshwater biodiversity, presents a grim picture.
"Rivers around the world really are in a crisis state," says Peter McIntyre, a senior author of the new study and a professor of zoology at the University of Wisconsin-Madison's Center for Limnology.
The analysis reveals that nearly 80 percent of the world's human population lives in areas where river waters are highly threatened posing a major threat to human water security and resulting in aquatic environments where thousands of species of plants and animals are at risk of extinction.
"What made our jaws drop is that some of the highest threat levels in the world are in the United States and Europe," says McIntyre, who began work on the project as a Smith Fellow at the University of Michigan. "Americans tend to think water pollution problems are pretty well under control, but we still face enormous challenges."
Peter McIntyre (Photo courtesy UW-Madison)
Huge investments in water technology and treatment reduce threats to humans, but mainly in developed nations, and leave biodiversity in both developed and developing countries under high levels of threat, according to the report.
"We find a real stew of chemicals flowing through our waterways," explains Vorosmarty, noting that the study represents a state-of-the-art summary, yet was unable to account for such things as threats from mining, the growing number of pharmaceuticals found in surface water and the synergistic effects of all the stresses affecting rivers.
What jumps out, say McIntyre and Vorosmarty, is that rivers in different parts of the world are subject to similar types of stresses - agricultural intensification, industrial development, river habitat modification and many other factors.
Compounding the problem is that some of the negative influences on rivers arrive in indirect ways. Mercury pollution, for example, is a byproduct of electricity generation at coal-fired power plants. It is emitted into the atmosphere and then is deposited on river surfaces.
"Flowing rivers represent the largest single renewable water resource for humans," notes Vorosmarty. "What we've discovered is that when you map out these many sources of threat, you see a fully global syndrome of river degradation."
Fresh water is the world's most essential natural resource, underpinning human life and economic development as well as the existence of countless organisms ranging from microscopic organisms to fish, amphibians, birds and terrestrial animals of all kinds.
People at Varanasi on India's Ganges River, March 2008. (Photo by Teoman Cimit)
But burgeoning human populations, damming, irrigation and other agricultural and engineering practices, chemical pollution, and the accidental as well as purposeful global redistribution of plants, fish, and other animal species have had far-reaching effects on rivers and their aquatic inhabitants.
"What we're doing is treating the symptoms of a larger problem," Vorosmarty says. "We know it is far more cost effective to protect these water systems in the first place. So the current emphasis on treating the symptoms rather than the underlying causes makes little sense from a water security standpoint or a biodiversity standpoint, or for that matter an economic standpoint."
The analysis used data sets on river stressors around the world. Built into state-of-the-art computer models, the data yield maps that integrate all of the individual stressors into aggregate indices of threat.
The same strategy and data, say Vorosmarty and McIntyre, can be used by governments worldwide to assess river health and improve approaches to protecting human and biodiversity interests.
The hard lessons learned by the developed world, says McIntyre, can help governments and planners in other parts of the world avoid making the same mistakes and experiment with new strategies for promoting water security and protecting biodiversity.
Instead of investing billions of dollars in expensive remediation technologies, strategies such as protecting watersheds, he advises, can reduce the costs of drinking water treatment, preserve floodplains for flood protection and enhance rural livelihoods.
"We've created a systematic framework to look at the human water security and biodiversity domains on an equal footing," Vorosmarty says. "We can now begin presenting different options to decision makers to create environmental blueprints for the future."
The work was executed under the aegis and support of two elements of the Earth System Science Partnership, which studies numerous aspects of global change science. Other contributors include the Global Water System Project headquartered in Bonn and the freshwater BIODIVERSITAS project of DIVERSITAS, the International Programme of Biodiversity Science in Paris.
The work was also supported by the U.S. National Science Foundation, NASA, the Global Environmental Facility, and the Society for Conservation Biology's Smith Fellowship Program.
In addition to McIntyre and Vorosmarty, authors of the report include Mark Gessner of the Swiss Federal Institute of Aquatic Science & Technology; David Dudgeon of the University of Hong Kong; Alex Prusevich and Stanley Glidden of the University of New Hampshire; Pamela Green of the City University of New York; Stuart Bunn of Griffith University, Australia; Caroline Sullivan of Southern Cross University, Australia; Cathy Reidy Liermann of the University of Washington; and Peter Davies of the University of Western Australia.
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