Complementing PABITRA High-Island Studies by Examining Terrestrial Plant Diversity on Atolls

The Pacific-Asia Biodiversity Transect (PABITRA) studies are based on a network of high-island biodiversity sites. These sites are structurally and historically complex. The majority of Pacific islands, in contrast, are low atolls with a common and simple flora and structure. As a result, atolls may serve as ‘‘controls’’ that may provide a way to assess impact of the upland high-island ecosystems on coastal regions of Pacific islands. Atoll studies can complement the PABITRA network because the gateway sites are near each other or separated from one another by one or more atolls. Such an addition will enhance interpretation of high-island ecosystems and their coastal zones because ecosystem surveys can be conducted quickly and accurately in atoll environments. We present results from quantitative studies of plant diversity from seven islets at Ailinginae Atoll in the northern Marshall Islands and discuss the value of this methodology as a way to enhance interpretation of the PABITRA data. The Pacific-Asia Biodiversity Transect (PABITRA) sites provide for collaborative investigations of the biodiversity on a series of islands in the Pacific. The sites were specifically chosen on several tropical high islands across several Pacific transects so that upland and lowland areas could be viewed as an integrated system. We support the choice of these focal sites, but we propose that they be supplemented with the addition of atoll sites. This expanded network will provide a broader range of opportunities to understand the function and structure of island ecosystems, including the role of people in these settings, while adding little additional cost to the overall project. The PABITRA participants have a wide range of research goals. Many of these focus on analyses of the indigenous forests and range from assessing their value as ecological reserves and the preservation of endemic species through appraising the watershed services that support the human populations. Atoll vegetation serves similar functions but operates without the topographic complexity or species richness of the high islands. There are obvious differences when atoll vegetation is compared with the more structurally complex vegetation found in the high islands, particularly in the upland areas. But it is comparisons of atoll communities with coastal communities of islands that are likely to be most interesting and perhaps most productive. A careful selection of sites may permit an evaluation of many types of relationships between upland and coastal areas because the atoll areas can serve as a control (without the upland area), particularly as this includes assessments of the resources needed to support human populations. We are certainly not the first investigators to propose the value of atolls and their small constituent islets as key elements in comparative island analyses. MacArthur and Wilson’s (1967) study has become a controversial classic (Stoddart 1992) in its predictions of trends in species richness over a range of island sizes. Such comparisons are not simple, of course, because high islands and atolls differ in many fundamental ways, such as their geologic history and the development of their soils. The PABITRA network provides many Pacific Science (2005), vol. 59, no. 2:261–272 : 2005 by University of Hawai‘i Press All rights reserved 1 Manuscript accepted 21 April 2004. 2 Corresponding author. 3 Department of Botany, University of Hawai‘i at Mānoa, Honolulu, Hawai‘i 96822. opportunities to include atolls. In the northern transect, for example, which crosses the Pacific from Belau (Palau) to Hawai‘i, there are hundreds of atolls dispersed near and between proposed high-island study areas. Indeed, most of the islands along this transect are atolls. As a result, it is possible to match high islands with atolls that share similar sealevel rainfall and that occur at similar latitudes. This study was designed, in part, to demonstrate the practicality of including atolls in the PABITRA design. In particular, we wanted to demonstrate that appropriate assessments could be done quickly and with a small research team. Our research broadly involves the terrestrial plant biodiversity of Ailinginae, the westernmost atoll in the Rongelap Atoll group in the Republic of the Marshall Islands (Figure 1). We established five general objectives: (1) obtain a complete inventory of the terrestrial plant species and collect vouchers of each species on each islet; (2) document the distribution of plants on the islets and collect information on the general structure of the vegetation; (3) determine the sampling efficiency of species data collected on random transects relative to a general checklist survey approach; (4) collect any botanical evidence of the locations and types of past anthropogenic activities; (5) build a baseline set of information that can be used for future studies. The specific hypotheses we wanted to address were as follows: (1) The same species are found on an islet if you use transect sampling or a ‘‘check listing’’ method (in chapter 3, ‘‘Vegetation’’ by D. Mueller-Dombois, J. D. Jacobi, and C. C. Daehler, in Biodiversity Assessment of Tropical Island Ecosystems, PABITRA Manual for Interactive Ecology and Management [D. Mueller-Dombois, K. W. Bridges, and C. C. Daehler, eds.] scheduled tentatively for publication in 2005; the book contents are available at http://www.botany.hawaii.edu/ pabitra) of thoroughly examining an islet. (2) The islets in the atoll have the same species. (3) Anthropogenic disturbances are found on all the larger islets. The opportunity to do this study came about when the Rongelap Atoll Local Government decided it was interested in setting aside some lands for conservation. This process required basic resource surveys, and the U.S. Fish and Wildlife Service in conjunction with the U.S. Department of the Interior were contacted for logistical, financial, and scientific support. Personnel from the University of Hawai‘i at Mānoa were included as part of the basic research team, along with individual members from several other academic institutions. Most of the financial and logistical support came from the Rongelap Atoll Local Government. They were able to secure a suitable ship, ship crew, small support vessels, dive master, and field assistants. Immediately after the expedition, the Rongelap Atoll Local Government, in cooperation with the government of the Republic of the Marshall Islands, began the process of establishing Ailinginae Atoll as the first national park of the Marshall Islands. They are also considering applying for United Nations Educational, Scientific, and Cultural Organization (UNESCO) World Heritage Site status.