New report paints devastating picture of world’s freshwater systems

The World Resources Institute says that freshwater systems are globally by far the most degraded ecosystem and that half of the world's wetlands were lost in the 20th century.

Pilot Analysis of Global Ecosystems (PAGE): Freshwater Systems released on 25 October by the Washington DC-based environmental research organisation concludes that although many regions of the world have ample freshwater supplies, four out of every 10 people currently live in river basins experiencing water scarcity. By 2025, the organisation says, at least 3.5 billion people, or nearly 50% of the world’s population will face water scarcity. Twenty-nine of the world’s river basins, with a projected population of 10 million each by 2025, will experience further scarcity, the World Resources Institute (WRI) says.

The report estimates that despite advantages to humans, dams, diversions or canals fragment almost 60% of the world’s largest 227 rivers, aiding degradation of freshwater systems worldwide with the only remaining large free flowing rivers in the tundra regions of North America and Russia, and in parts of Africa and South America. On almost every continent, river modification has affected the natural flow of rivers to such an extent that many of the world’s most important rivers, such as the Colorado, Huang-He (Yellow), Indus, Ganges, Nile, Syr Darya, and Amu Darya, no longer reach the ocean during the dry season.

Already, the report says, humans are withdrawing about half the planet’s readily available river water, a trend which has increased at more than twice the rate of population growth. With human populations continuing to grow, water scarcity is estimated to increase dramatically in the next decades.

Human modification of water systems, together with the introduction of non-native species, pollution, and over-exploitation has led to more than 20% of the world’s known 10,000 freshwater fish species becoming extinct, threatened, or endangered in recent decades, the report says. In the US, which has the most comprehensive data on freshwater species, 37% of freshwater fish species, 67% of mussels, 51% of crayfish and 40% of amphibians are threatened or have become extinct. Studies of the introduction of non-native fish in Europe, North America, Australia, and New Zealand, reveal that 77% of them resulted in the drastic reduction or elimination of native fish species. In North America, alone, 27 species and 13 subspecies of native fish became extinct in the last century largely due to the introduction of non-native fish.

The report said that water-borne diseases from fecal pollution of surface waters continue to be a major cause of illness in the Third World. While surface water quality has improved in the United States and Western Europe, nutrient loading from agricultural runoff continues to be a major problem.

Although rivers, lakes and wetlands contain only 0.01% of the world’s freshwater, the global value of freshwater services is estimated in the trillions of dollars, WRI says. “We need to value freshwater ecosystems not only from the goods they produce, like fish and clams, but also the services they give, like the filters and nurseries that wetlands provide,” said Carmen Revenga, one of the report’s co-authors.

The report on freshwater systems is the first of a series WRI will release over the next six months, forming the most comprehensive assessment of the state of the world’s ecosystems, the group says. The reports will set the stage for the Millennium Ecosystems Assessment (MEA) that will be launched next year by WRI, the United Nations Environment Program, and other international agencies. The MEA is expected to fill in the data gaps identified by the WRI reports through the participation of hundreds of the world’s leading scientists who will be mobilised for a $20 million, four-year effort.

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