It's the second such day designated by the U.S. Senate to "encourage the people of the United States to become educated about, and aware of, threats to species, success stories in species recovery, and the opportunity to promote species conservation worldwide."

Nearly 400 organizations nationwide are planning special events. The Salt Lake City-based Southern Utah Wilderness Alliance is part of the coalition bringing attention to the day.

At Hogle Zoo in Salt Lake City, several conservation-minded shows are planned, part of the usual programs. Zoo spokeswoman Holly Braithwaite said at the World of Flight show, visitors can get an up-close look at birds from around the world, including a few endangered species and a few species that have been a focus of conservation efforts.

The Tucson-based Center for Biological Diversity is celebrating the day with a Web site describing 100 endangered species success stories. They include the Utah prairie dog, the American peregrine falcon, the Gray wolf and the Bald eagle.

"The Endangered Species Act is one of America's most successful conservation laws," said Kieran Suckling, policy director for the center.

Wildlife, conservation and environmental advocates say critics of the law overstate the costs of protecting plant and animal species while minimizing the benefits. They say Americans are healthier and safer when plants, animals and fish have clean air, land and water.

Meanwhile, critics say too few species have been saved under the law despite the expense to government and private landowners.

fahys@sltrib.com