With 510 acres, Big Sand Mound is home to undisturbed prairies, shallow ponds and woodlands, and it has the highest concentration of threatened and endangered species in the state. Of more than 400 different plants at the site, 80 percent are native. The preserve is jointly owned by MidAmerican Energy Company and Monsanto Company, with MidAmerican Energy owning 420 acres and Monsanto owning 90. Dr. Thomas Rosburg, professor of ecology and biology at Drake University, explains the geological history and unique biodiversity of the Big Sand Mound Nature Preserve in Muscatine, Iowa.