Zebra musselsJune 1, 1942: The Grand Coulee Dam is dedicated in Washington state. While the dam aids navigation and generates hydroelectric power on the Columbia River, it blocks salmon runs in 1,000 miles of waterways upstream from the dam.

June 1, 1988: The zebra mussel (at right), a tiny native of the Caspian Sea, is discovered in Lake St. Clair, near Detroit. The mussels reproduce rapidly and like living in fast-moving water. Within a year, they've gathered by the millions around the intake pipes of factories and power plants. The city of Monroe, Mich., shuts down its public water supply for two days due to the infestation. The mollusk is believed to have hitched a ride in ballast water from Asia to Michigan.

June 1, 2000:  Over 1,500 politically-conservative religious leaders sign the Cornwall Declaration on Environmental Stewardship.  The document acknowledges the Biblical concept of environmental "stewardship," but rejects "unfounded" assertions on issues like climate change.  Later investigations reveal that the Cornwall Alliance enjoys strong financial support from fossil fuel interests.

June 1, 2002: A study published in the journal Environmental Health Perspectives says that blood-lead levels in U.S. children have dropped 80 percent since leaded gasoline was banned in 1976.

Photo: U.S. Department of Agriculture/AP

This feature is compiled by Peter Dykstra, an MNN contributor and publisher of Environmental Health News and The Daily Climate.