Reconstruction of the Ecosystem in the Bonin Islands

Abstract

The eradication of invasive species is one way to maintain biodiversity on oceanic islands. In the Bonin Islands, eradication programs for goats, pigs, rats, Bischofia javanica, and so on, are either ongoing or complete on several islands. However, the islands are still suffering from the impacts of increasing numbers of invasive species, such as green anoles ( Anolis carolinensis ) and flatworms ( Platydemus manokwari ), which are hard to eradicate completely because of their high density and small body size. Control measures to prevent range expansion have been developed for these species. Techniques to conserve threatened populations, such as through artificial habitats and captive breeding, have also been implemented. Because the number of species introduced to the islands is increasing, an adequate daily monitoring system is required to detect them. Although controlling introduced species is expected to restore the native ecosystem, countermeasures do not always produce the desired outcomes. For example, the eradication of feral goats caused subsequent increases in invasive plants that had been released from heavy grazing pressure. Pre- and post-eradication monitoring is required to ensure the success of eradication programs. A better understanding of interspecific relationships is the only solution to such a problem. When some species in a native ecosystem have gone extinct, their ecosystem function may be filled by long-established introduced species, whose subsequent removal could cause ecosystem collapse. The construction of a sustainable, stable ecosystem including both native and introduced species is the realistic goal of conservation in the Bonin Islands.