Kesterson National Wildlife Refuge

One of a dwindling number of freshwater marshes in California's San Joaquin Valley, Kesterson National Wildlife Refuge achieved national notoriety in 1983 when refuge managers discovered that agricultural runoff was poisoning the area's birds. Among other elements and agricultural chemicals reaching toxic concentrations in the wetlands , the naturally occurring element selenium was identified as the cause of falling fertility and severe birth defects in the refuge's breeding populations of stilts, grebes, shovellers, coots, and other aquatic birds. Selenium, lead , boron, chromium, molybdenum, and numerous other contaminants were accumulating in refuge waters because the refuge had become an evaporation pond for tainted water draining from the region's fields.

The soils of the arid San Joaquin valley are the source of Kesterson's problems. The flat valley floor is composed of ancient sea bed sediments that contain high levels of trace elements, heavy metals , and salts. But with generous applications of water, this sun-baked soil provides an excellent medium for food production. Perforated pipes buried in the fields drain away excess water—and with it dissolved salts and trace elements—after flood irrigation . An extensive system of underground piping, known as tile drainage , carries wastewater into a network of canals that lead to Kesterson Refuge, an artificial basin constructed by the Bureau of Reclamation to store irrigation runoff from central California's heavily-watered agriculture. Originally a final drainage canal from Kesterson to San Francisco Bay was planned, but because an outfall point was never agreed upon, contaminated drainage water remained trapped in Kesterson's 12 shallow ponds. In small doses, selenium and other trace elements are not harmful and can even be dietary necessities. But steady evaporation in the refuge gradually concentrated these contaminants to dangerous levels.

Wetlands in California's San Joaquin valley were once numerous, supporting huge populations of breeding and migrating birds. In the past half century drainage and the development of agricultural fields have nearly depleted the area's marshes. The new ponds and cattail marshes at Kesterson presented a rare opportunity to extend breeding habitat , and the area was declared a national wildlife refuge in 1972, one year after the basins were constructed. Eleven years later, in the spring of 1983, observers discovered that a shocking 60% of Kesterson's nestlings were grotesquely deformed. High concentrations of selenium were found in their tissues, an inheritance from parent birds who ate algae, plants, and insects—all tainted with selenium—in the marsh.

Following extensive public outcry the local water management district agreed to try to protect the birds. Alternate drainage routes were established, and by 1987 much of the most contaminated drainage had been diverted from the wildlife refuge. The California Water Resource Control Board ordered the Bureau of Reclamation to drain the ponds and clean out contaminated sediments, at a cost of well over $50 million. However, these contaminants, especially in such large volumes and high concentrations, are difficult to contain, and similar problems could quickly emerge again. Furthermore, these problems are widespread. Selenium poisoning from irrigation runoff has been discovered in least nine other national wildlife refuges, all in the arid west, since it appeared at Kesterson. Researchers continue to work on affordable and effective responses to such contamination in wetlands, an increasingly rare habitat in this country.

[Mary Ann Cunningham Ph.D. ]

RESOURCES

BOOKS

Harris, T. Death in the Marsh. Washington, DC: Island Press, 1991.

PERIODICALS

Claus, K. E. "Kesterson: An Unsolvable Problem?" Environment 89 (1987): 4–5.

Harris, T. "The Kesterson Syndrome." Amicus Journal 11 (Fall 1989): 4–9.

Marshal, E. "Selenium in Western Wildlife Refuges." Science 231 (1986): 111–12.

Tanji, K., A. Läuchli, and J. Meyer. "Selenium in the San Joaquin Valley." Environment 88 (1986): 6–11.

ORGANIZATIONS

Kesterson National Wildlife Refuge, c/o San Luis NWR Complex, 340 I Street, P.O. Box 2176, Los Banos, CA USA 93635 (209) 826-3508,