But there is an even more insidious side to this invasion. Exotic species also out-compete and replace native plants like horticultural body snatchers. This loss of native plants represents an overall loss of habitat and food sources for native wildlife. Consider the impact of the Bradford pear and its overuse as a street and landscape tree. Unlike a native ornamental tree, such as a viburnum or red chokeberry, which can provide food for dozens of bird species, the brittle Bradford pear attracts only European starlings, a winged plague in their own right, which help carry the invader's seeds far and wide in an example of sinister symbiosis.
English ivy is another example.
It displaces native groundcovers, inevitably escapes into natural areas, and eventually mutates from groundcover to tree strangler. Unfortunately, the invasion can never be completely halted. Once a non-native species is successfully introduced, it is almost impossible to eradicate it completely. However, we can strike an effective blow for biodiversity in several important ways. First, know your enemy.