Multiple environmental stressors, such as agricultural runoff, pollution and invasive species, threaten rivers that serve 80 percent of the world's population, around five billion people, according to researchers from The City University of New York, University of Wisconsin and seven other institutions.

These same stressors also endanger the biodiversity of 65 percent of the world's river habitats and put thousands of aquatic wildlife species at risk.

The findings, to be reported Thursday in journal Nature, 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.

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.

The researchers noted that causes of degradation of many of the developing world's most threatened rivers bear striking similarities to those of rivers in similar condition in wealthy countries, adding that their findings are "conservative," since there is insufficient information to account for additional stressors like pharmaceutical compounds and mining wastes.