National parks provide good habitats for many kinds of animals, yet natural resources in parks are threatened from contaminants and other environmental concerns. The young CSI investigators play food web games showing how toxins like mercury or DDT get into the park and accumulate from prey to predator. We take a tour of the salamander's forest habitat and help the park "monitor" its salamander population, recording data in a field notebook. At the pond we collect and identify dragonfly larvae, a species that can help park scientists tell if Acadia National Park watersheds are healthy. From these field experiences, students are introduced to the important role science plays in conservation decision-making.