More than half of the world’s lakes and reservoirs face massive ecological threats
Water experts have warned that one billion people are at risk from over-use, water withdrawals and pollution of the world’s lakes and reservoirs, which hold nearly 90% of all surface liquid fresh water.
The panel of experts for the forthcoming 3rd World Water Forum told delegates at the 9th International Conference on the Conservation and Management of Lakes held in Shiga, Japan, from 11-16 November, said that many of the hazards to the world’s five million lakes derive from a growing global demand for water, which will be increased as the world population rises by nearly two billion people by the year 2025 (see story in the same section). The experts say that the threats to lakes are difficult to manage because they are often interwoven, and that attacking one threat often leads to the increase of another threat. The principal threats worldwide are:
- accelerated eutrophication, which affects 54% of the lakes in the Asia-Pacific region, 53% in Europe, 28% of those in North America, and 41% of those in South America;
- chemical pollution, which is the second most commonly cited threat to lakes;
- alien plant and animal species, either introduced into lake environments in the ballast water of ships, as part of the aquarium trade, from small boats travelling between lakes, or in bait and by escaping from aquaculture, with some intentionally introduced to boost fishery production or to control another exotic species;
- acidification, which is a serious problem in most of central and northern Europe, the northeastern United States and southeastern Canada, Australia, New Zealand, Japan, and China, with many lakes in Scandinavia and the affected regions of North America becoming so acidic in the past few decades that they can no longer sustain the diverse forms of life originally found there; and
- water withdrawals, which have risen to 3,800 cubic kilometres per year, and one study estimating a six-fold increase in water withdrawals from lakes and rivers between 1990 and 1995.
In industrialised countries, shallow lakes are the most endangered, especially those situated in areas of intensive agriculture, or which have been depleted for drinking water and industrial uses. Those that are most at risk include the US’ second largest lake, Lake Okeechobee, which has an average depth of just 10 feet (3 metres), Arre Lake in Denmark, Hungary’s Lake Balaton, the Aral Sea between Kazakstan and Uzbekistan, which has dropped in area from the world’s fourth largest lake to the eighth largest, and the world’s deepest lake, Russia’s Lake Baikal, containing about one-fifth of the world’s fresh surface water, facing pollution from industrial plants.
In the developing world, some of the most threatened lakes include Africa’s largest, Lake Victoria, Lake Chad (see related story), which has been reduced to one twentieth its size in four decades, and Taihu Lake in China, where experts say you can practically walk on its surface, because of severe pollution.
Once a lake becomes degraded, it takes a long time and a great deal of effort to restore it to health and, as a consequence, successful restorations are rare, particularly in the case of large lakes, the experts say. One success story is Lake Washington near the US city of Seattle, which was highly eutrophic until the 1970s, but was restored by installing a wastewater treatment system and diverting the treated effluent out of the lake’s watershed. Managing lakes is also very difficult, not only entailing resolving important technological, financial, and institutional issues, but also requiring support from industry and the public as well as government. A participatory, watershed-based approach is much more difficult to achieve for lakes in developing countries, where political instability and the lack of financial resources are more common.
“Lakes are among the most vulnerable and difficult to restore of all natural ecological systems, but they have been widely ignored even as they have deteriorated,” said Masahisa Nakamura, Director of Japan’s Lake Biwa Research Institute in Shiga. Lakes in both industrial and developing countries are endangered, though rich countries have the resources to begin adopting policies to save their lakes.”
“Natural lakes, especially large ones, are of great economic, ecological and cultural importance, with at least one billion people depending directly on them for their livelihood and for drinking water,” says Dr. Mahmoud Abu Zeid, Minister of Irrigation and Water Resources of Egypt and President of the World Water Council.
The Lakes Conference is one of a series of international meetings leading up to the 3rd World Water Forum, which is sponsored by the World Water Council every three years and will highlight actions being taken to implement solutions to global water problems. The conference will take place in March 2003 in Kyoto, Japan.