Invasive non-native ungulates decimate native plants that have evolved without protective spines, tough bark, unpalatable taste, or poison sap. Non-native predators from house cats to ants overwhelm species with no innate fear or defense against predation. Foreign diseases (avian malaria and pox) spread by alien mosquitoes have caused extinction of most native honeycreepers.
Haleakalā's strategy is to fence the park to exclude alien ungulates; remove all populations of feral goats, pigs and deer; and place snares at remote areas to intercept any individual ungulate that penetrates the boundary fence.
The ubiquitous mobility of modern humans, and frequent transport of accompanying biotic organisms (accidental or deliberate) now overwhelms an island ecosystem that evolved in remote isolation. Haleakalā partially thwarts this ecological destruction. The park staff vigorously defends its native Hawaiian biodiversity from invasive aliens.