Gray wolf March 21, 1981: Inspired by author Edward Abbey and his book "The Monkey Wrench Gang", activists unfurl a large roll of black plastic down the face of the Glen Canyon Dam , depicting a symbolic crack in the dam. The controversial dam had changed the ecosystem of a large stretch of the Colorado River. The event spawns the group Earth First!

March 21, 1994: The U.N. Framework Convention on Climate Change (UNFCCC) takes effect, the first global agreement on addressing climate change.

March 21, 1995: Gray wolves are released in Yellowstone National Park . The wolves (one seen at right), wiped out in much of the West in the early 1900s, are now the object of a long court battle between conservationists and ranchers, who fear that the wolves will prey on livestock. Within ten years, the wolf restoration project is considered a complete success.

Photo: USFWS Endangered Species /Flickr

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