Among the greatest environmental challenges facing Acadia National Park is the presence and threat of invasive species. Non-native species, especially those considered invasive, threaten communities of native plants and animals across the United States. In national parks, more than 2.6 million acres of parklands are affected by invasive plant species, and 234 National Park Service areas have invasive animals in need of management.
Invasive species are those which do not naturally occur in a specific area and cause ecological and economic damage. The majority of invasive species are also non-indigenous but some native species can become invasive too (i.e. deer in some areas). Many different organisms can become invasive pests including plants, vertebrates, invertebrates, fungi, and microorganisms. Non-native invasive species can be introduced purposely or accidentally. An intentional introduction could be a plant from Asia that is planted ornamentally in gardens and then escapes. An accidental introduction could occur with contaminated containers shipped from overseas. Invasive pests are successful in establishing populations on alien turf because their natural predators (disease, herbivore/carnivores) do not exist in the new territory and therefore can out-compete native species for resources. Invasive species can eliminate their native counterparts or destroy whole populations if gone unchecked.