Garlic-mustard (Alliaria petiolata) dominating the understory on Virginius Island.
Non-native species, also known as exotic, alien, or introduced species, are defined as species that occur in a certain place due to deliberate, accidental, direct, or indirect human actions. Both animal and plant species are capable of becoming established in the wild when they are brought into an area that meets their living requirements. Many exotic plant species begin as ornamental landscape plantings, while introduced animal species often become established due to humans releasing them outside of their normal range.
Invasive, non-native species are capable of displacing native species, and therefore threaten the diversity and integrity of indiginous communities. Fifty invasive, non-native plant species have been identified within the park, including garlic-mustard (Alliaria petiolata), Japanese honeysuckle (Lonicera japonica), tree-of-heaven (Ailanthus altissima), Japanese stilt-grass (Microstegium vimineum), and English ivy (Hedera helix). Exotic animal species found in the park include gypsy moth (Lymantria dispar ), hemlock woolly adelgid (Aldeges tsugae), European starlings (Sturnus vulgaris) and house sparrows (Passer domesticus).