How healthy is that wetland? Count the parasites in common snails to find out. The more species of parasites, the healthier the marsh, as it implies the presence of all requisite hosts. The goal of this project is to test the practical validity of the concept in the field and whether it can be adapted into a tool for inexpensively monitoring wetland biodiversity. To date, biologists have collected common horn snails and counted the number and kinds of trematode (fluke) parasites infecting them at more than 30 wetlands in California. They are in the process of calibrating these snail-parasite counts with traditional field surveys of fishes and benthic invertebrates at 16 of those wetlands. Scientists presented their work at the most recent Ballona Wetlands Science and Research Symposium, hosted by the Santa Monica Bay Restoration Commission, and are in continuing dialog with wetland managers about their findings. UC Berkeley’s Lawrence Hall of Science is incorporating aspects of this project into its public science curriculum and will soon be taking students in its East Bay Academy of Young Scientists program out into the field to collect and dissect horn snails.