Aliens are invading the park! Of the more than 500 species of plants within Wind Cave National Park, more than 100 are non-native. Some non-native, such as Canada thistle, can create monocultures that can threaten the diversity of the prairie. In a monoculture, only one plant thrives. This loss of species diversity affects not only the prairie, but the animals that depend upon the prairie as a food source. The park is researching several non-native plants to find ways to control them.