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Mono Lake: Solving an Environmental Dilemma
| Article
# : |
14651 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
5 / 1988 |
3,381 Words |
| Author
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Daniel B. Botkin and John A. Wiens
Daniel B. Botkin is professor of biology and environment
studies at the University of California, Santa Barbara. His
book, Discordant Harmonies: A New Ecology for the Twenty-first
Century, will be published by Oxford University Press. John A.
Wiens is professor of ecology in the Department of Biology at
Colorado State University. His just-completed book The Ecology
of Bird Communities will be published by Cambridge University
Press. |
Mono Lake, a strangely beautiful salt lake in the high desert of east central California, is an important resource for more than one million birds and for the more than six million people of metropolitan Los Angeles. But whether the two groups can continue to share this resource has become a major environmental issue.
The birds have used the lake as a breeding area and source of food for thousands of years. The city of Los Angeles began to divert fresh water from the streams that flow into the lake in 1941; these diversions currently provide 17 percent of the city's water supply, enough to serve 500,000 people. Largely as a result of these diversions, the surface elevation of the lake has dropped, its volume and surface area have decreased, and the salinity of the lake has doubled.
Mono Lake became the center of controversy in the 1970s. It supports the second-largest breeding colony of California gulls in the world, and the lowering lake level caused several islands used as breeding sites to become bridged to the mainland. Coyotes crossed the bridges, preying on gull chicks and disrupting breeding. With further reductions in lake levels, additional breeding islands became exposed to these predators, and reproductive success plummeted. Even after the lake level rose during wet years and made these sites islands again, the gulls seemed reluctant to reoccupy them for several years.
The controversy involves more than gulls, however. The lake's unusual chemistry supports a huge annual production of brine flies and brine shrimp, providing food for other water birds that stop at the lake to molt and feed during migration. Many fear that, as lake salinity increases, salt levels will exceed the tolerance of the shrimp and flies, destroying the food base of the birds.
Air quality is also affected. When the lake recedes, large expanses of lake bottom are exposed. High winds sweeping across these playas pick up dust and carry it over considerable distances. Substances such as arsenic in these dust clouds may exceed air-quality standards several fold.
How important are these concerns? Like so many other environmental issues, the answer for Mono Lake has not been clear. In the last year, however, the situation has changed. Two studies have produced unusually clear answers: one conducted by the National Academy of Sciences with funds from the U.S. Forest Service, and other carried out by the University of California, Santa Barbara, under a
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