Impact of Alien Plants on Hawai'i's Native Biota.
AbstractOver 4, 600 species of plants have been introduced into the Hawaiian Islands over the last 200 years. Only 86, less than 2% of the total, have become serious pests of native ecosystems. Of these, the most significant are Andropogon virginicus, Clidemia hirta, Lantana camara, Leucaena leucocephala, Melinis minutiflora, Myrica faya, Passiflora mollissima, Pennisetum clandestinum, Pennisetum setaceum, Psidium cattleianum, Rubus argutus, and Schinus terebinthifolius. All 86 species are discussed with regard to their impact on the ecosystem, dispersal mechanism, fire tolerance, potential for biological control, and their distribution and principal infestation sites. Twenty-eight (32%) are invasive weeds; the remainder generally require some form of disturbance in order to become established.
The lowland ecosystems have suffered the most disruption from alien species because of agriculture, fire, and urbanization. However, all vegetation types have been affected to some degree. The ecosystems least impacted are alpine habitats, rain forests, and bogs, although they are coming under increasing pressure.
A number of strategies are discussed which may help to ameliorate weed problems. Greater effort by government is needed to educate the public on the need for importation control and to enforce regulations. Mechanical and herbicidal control is discounted except in small areas. Biological controls offer considerable hope, but there are many problems associated with this strategy.
The unique flora and fauna of the Hawaiian islands is seriously threatened by alien plants. Many native species have already been extirpated. Unless importation of aliens and the continuing disturbance of the native ecosystems is stopped, the prognosis for the remaining native biota is grim.