The sequence, Larison found, begins with willows, an important winter forage for ptarmigans. Willows take up the metal through their roots and concentrate it in their branches and leaves, which are then eaten by birds and other animals.
Larison says the study's most important conclusion is that cadmium isn't just transported by water. "No one has ever anticipated these toxins moving through terrestrial ecosystems with such ease," he says. Though Larison conducted his study in central Colorado's "ore belt," where mining over the last century has left cadmium in ecosystems, he says the metal can harm wildlife even without human activity.
The Environmental Protection Agency joined the OSU researchers this summer, and Larison says the agency plans to invest more money in these issues in coming years.
The study is available in the July 13 issue of Nature, or at www.nature.com.