HEAR bibliography
Inventory of seabirds, plants, and arthropods of twenty offshore islets in the main Hawaiian Islands
Eijzenga, Heather and David J. Preston. (2008)

Biological inventories were conducted on 20 islets offshore 7 of the main Hawaiian Islands: Niihau (Lehua), Kaua.i (Moku'ae'ae), Oahu (Mokoli'i, Kapapa, Kaohikaipu, Manana), Maui (Moke'ehia, Moku mana, Mokuhuki, Mokupipi, Pu'uku, 'Alau) Lanai (Po'opo'o, Pu'u pehe, Ki'ei), Molokai (Moku manu, Mokuho'oniki, Kanaha), and Kaho.olawe (Pu'u koa'e, 'Ale'ale). Our primary focus was to complete baseline arthropod surveys, but due to the expense and difficulty of accessing many of the islets, we took the opportunity to conduct seabird and plant surveys as well. All arthropods were collected and taken to Bishop Museum for identification and curation while plant and seabird identifications were made in the field. The offshore islets surveyed are important sanctuaries for at least three species of seabird and provide critical habitat for many native plant species. Of the 129 total plant species found during our survey, 32 were endemic to Hawai.i and 25 were indigenous including nine species listed as endangered or species of concern. In general, Kaohikaipu, Moku mana, Mokuho'oniki, Kanaha, Pu'u koa'e, and 'Ale'ale represent the islets with the most intact, diverse, or unique native flora. The arthropod community, however, appears to have been decimated on all of the islets. Of the 155 total arthropod species collected, only 15 were native. Kaohikaipu, with four endemic and two indigenous arthropod species, had the highest native diversity, but no natives were found on the majority of islets surveyed. The islets varied dramatically in size, topography, height, rainfall, isolation, and accessibility, but all were threatened by invasive species. Introduced weeds were ubiquitous and ten of these are of particular concern because they are known to be invasive. Some islets are already dominated by these noxious species. For example, on three islets (Manana, Po'opo'o and Pu'u pehe) the invasive grass Cenchrus ciliaris forms an almost complete monoculture at the exclusion of native taxa. Other islets have incipient weed populations that will follow a similar path if left untreated. Introduced ants are also a widespread problem. Some of the particularly aggressive species have undoubtedly played a role in the demise of native arthropod populations. They may also affect the plant community and disrupt entire colonies of nesting seabirds. Humans can also be seen as a major threat as visitors trample weeds, crush burrows, and introduce new pest species. Fortunately, the small size and discrete boundaries of the offshore islets makes eradication and restoration feasible management options and their relative isolation helps prevent re-invasion. A restoration program coupled with education and community involvement will help safeguard remaining native populations and restore those that have been degraded.