Even though the number of plant species present in the area is higher by one, the ecological interactions that drive the Everglades ecosystem have collapsed where Melaleuca has invaded because its dominance contributes nothing to other organisms. Diversity is important, then, only when the species that can be said to create it are contributing members of their ecosystem. This contribution is most likely when species have evolved together over long periods of time.
The grassland birds that breed in the Everglades cannot nest in Melaleuca groves, and they find fewer insects to eat because native insects cannot eat Melaleuca leaves (Costello et al. 1995). Alligators cannot make their wallows or find food in Melaleuca groves, and so they have lost hundreds of thousands of acres of habitat. Butterflies cannot find their host plants, egrets cannot hunt the fish they eat, and hummingbirds cannot find the nectar they need to survive from day to day.
