California has the largest number of rare plants and animals of any state in the nation. In California, San Diego is a hotspot of biodiversity. There are more species of plants here than almost anywhere else in the world. Or at least there were more species of plants than almost anywhere else in the world. As the region has developed, shopping malls, schools, roadways, office buildings, and homes cover what was once vernal pools, and other rare habitat areas. As a result, San Diego County is also on the hotlist for endangered species. In this episode, we meet Dr. John Clark, the charismatic scientist who is executive director of the Center for Plant Conservation, which recently relocated from the Missouri Botanical Garden to join forces with the San Diego Zoological Society. Dr. Clark takes us to see examples of endangered plants, many of which are all around us -- we simply don't recognize them. We talk with Dr. Clark about why these plants are important, what exactly it means to be an "endangered" plant, and what, if anything, we can do to slow the rate of plant extinction both locally and worldwide.