The parkway's 4,580 acres are home to at least 81 plants and animals considered rare, threatened, or endangered in Virginia or Maryland. These include 37 species of vascular plants, 2 vertebrates, and 19 invertebrates.
Many of these rare species are associated with the plant communities found in few places in the Potomac River Gorge. Some of these habitats have names that make them sound every bit as exotic as they are, like Bedrock Terrace Rim Xeric Forest and Bedrock Terrace Xeric Savanna.
Natural areas within the park are extremely biodiverse, and parts of these areas have not been studied fully yet. As recently as 2011, a species of caddisfly new to science, Neophylax virginica, was discovered in Turkey Run. Each new study yields first records of species that live in the area.