Multiple environmental stressors such as agricultural runoff, pollution and invasive species, researchers warn, threaten rivers that serve 80 percent of the world's population, that amounts to about 5 billion people.
These same stressors endanger the biodiversity of 65 percent of the world's river habitats and put thousands of aquatic wildlife species at risk, according to researchers from The City College (CCNY) of The City University of New York (CUNY), University of Wisconsin and seven other institutions.
The findings come from the first global-scale initiative to quantify the impact of these stressors on humans and riverine biodiversity.
The research team produced a series of maps documenting the impact using a computer-based framework they developed.
"We can no longer look at human water security and biodiversity threats independently," said the corresponding author, Dr. Charles J. Vörösmarty.
"We need to link the two. The systematic framework we've created allows us to look at the human and biodiversity domains on an equal playing field," he said.
The framework offers a tool for prioritizing policy and management responses to a global water crisis.
"As is the case with preventive medicine, our study demonstrates that diagnosing and then limiting threats at their local source, rather than through costly remedies and rehabilitation, is a more effective and sensible approach to assure global water security for both humans and aquatic biodiversity, " notes Professor Vörösmarty.
Among the stressors analyzed were the effects of pollution, dams and reservoirs, water overuse, agricultural runoff, loss of wetlands and introduction of invasive species.
High incident threat levels to human water security were found in developed and developing nations around the world.
Affected areas include much of the United States, virtually all of Europe and large portions of Central Asia, the Middle East, the Indian subcontinent and eastern China.
A strategy called integrated water resource management, which balances the needs of humans and nature, would best meet the dual challenge of establishing human water security and preserving biodiversity in the developing world.
The findings were reported in the September 30 issue of Nature.