Special Ecological Areas: an Approach to Alien Plant Control in Hawaii

A Special Ecological Areas approach to alien plant management was adopted at Hawai`i Volcanoes National Park in 1985. The approach involves control of widespread, disruptive alien plant species in Special Ecological Areas, which are intensive management and research units in the Park. Special Ecological Areas management developed from these perceptions: 1) unmanaged alien species were affecting many of the most valuable biological sites in the Park; 2) some widespread alien plants had increased their ranges dramatically in recent years; 3) alien plant control efforts were focused on species in degraded parts of the Park; and 4) biological control was not a panacea for widespread weed problems. Areas were selected according to the following criteria: Representativeness/rarity of vegetation type, vegetation intactness, plant species diversity/richness, manageability, presence of rare flora, preserve design considerations, immediacy of threat from alien plants, and research and interpretive values. Eleven species were targeted for control in Special Ecological Areas, were usually monitored by counting individuals encountered, and were controlled on an annual basis. All target species have declined sharply since initiation of treatment. For example, density or biomass of the three most important alien species, firetree (Myrica faya), strawberry guava (Psidium cattleianum), and kahili ginger (Hedychium gardnerianum), declined by 86%, 85%, and 96% respectively in Special Ecological Areas treated from 1985 to 1988. The number of worker days required for control efforts declined 73% over the same interval. Tentative conclusions about alien plant control in Special Ecological Areas are: 1) populations of alien plant species can be significantly reduced and maintained at very low levels after three to four years of control work; 2) recruitment of alien plant species is usually very low; 3) continued follow-up treatments are required in all areas and may be needed indefinitely; 4) workloads drop significantly after initial control efforts; and 5) Special Ecological Areas serve as effective models for management of other areas. Special Ecological Areas also provide a focus for research on and monitoring of native and alien species as related to management. Permanent monitoring systems will soon be established for birds, Hawai`ian bats (Lasiurus cinereus semotus), invertebrates, and rare