The sand dunes, marshes and backwaters of the upper Mississippi River, including the Weaver Dunes of southeastern Minnesota, hold one of the largest remaining populations of the Blanding's turtle, which the Minnesota Department of Natural Resources already classifies as threatened. A population in Valentine National Wildlife Refuge in northern Nebraska, where the species is classified as at-risk, is more secure but still vulnerable.

In response to a petition from the Center for Biological Diversity, an environmental advocacy group, the U.S. Fish and Wildlife Service last week began a formal assessment of whether 20 amphibians or reptiles found in various parts of the country, including the Blanding's turtle, and one plant species should be listed as endangered or threatened under the Endangered Species Act. Such listings would give them greater protection.

The center says the fragmented, remnant populations of Blanding's turtles across their historic range aren't enough to sustain what's left of the species.