1Interdisciplinary Approach for Sustainable Land Management ofAtoll IslandsHajime KAYANNE,1 Masashi CHIKAMORI,2 Hiroya YAMANO,3,4 Toru YAMAGUCHI,5Hiromune YOKOKI6 and Hiroto SHIMAZAKI3
1Department of Earth and Planetary Science, University of Tokyo, Hongo, Tokyo 113-0033, Japane-mail: kayanne@eps.s.u-tokyo.ac.jp
2
Faculty of Informatics, Teikyo Heisei University,Ichihara, Chiba 290-0171, Japan
3Social and Environmental Systems Division, National Institute for Environmental Studies,
Tsukuba, Ibaraki 305-8506, Japan
4Institute de Recherche pour le Développement, BP A5 Nouméa Cedex, New Caledonia
5Department of Ethnology and Archaeology, Keio University, Mita, Tokyo 108-8345, Japan
6Center for Water Environmental Studies, Ibaraki University, Hitachi, Ibaraki 316-8511, JapanAbstract
Atoll islands are low, flat land on atolls with a maximum elevation of one to two meters. They are
under crisis of submergence due to rising sea levels in this century. The formation and maintenance ofatoll island landforms are regulated not only by physical but also by ecological processes. The source ofsand constituting the islands is calcifying organisms, and coral reefs on the ocean side of the islands act
as a natural breakwater and provide bioclastic materials. Bleaching induced by global warming degrades
the ecological process of island formation. Moreover, the traditional vegetation management system acts
to stabilize landforms, but urbanization of atoll islands disrupted this human process, thereby increasing
the vulnerability of these islands to environmental stresses. For sustainable utilization and developmentof atoll islands, it is fundamental to evaluate the interaction between natural and human processes
through interdisciplinary research among geomorphology, anthropology and coastal engineering. Theultimate goal of the research is to establish a diagnosis of the present status and future response of atoll
islands to environmental changes, and to establish an ‘atoll island model’ to predict their landformchanges in response to future sea levels. Another objective is to re-evaluate traditional human management systems of island landforms and vegetation in effective utilization of resources and land. Remotesensing and GIS would provide effective tools to extend the results obtained in model fields to otheratoll islands in general.
Key words: atoll, atoll Island, landform, land management, sea level rise

1. Atolls and Atoll Islands
The atoll is one of the three major types of coral
reef landforms: a ring-shaped reef enclosing a shallow
lagoon. The diameter of the ring may be as large as
several tens of kilometers (Fig.1) to as small as a few
kilometers (Fig. 2). The width of the reef, which forms
the ring, is generally one to two kilometers at maximum, and the depth of the lagoon is several tens ofmeters. If a coral reef forms a circular or elliptical flat
without a lagoon, it is called a table reef.
Approximately 500 atolls are distributed worldwide: approximately 400 in the Pacific Ocean, 70 in
the Indian Ocean, and 30 in the Caribbean Sea (bluedots in Fig. 3). Most of the atolls exist in the Pacific
Global Environmental Research9(1)/2005: 1-7
printed in JapanOcean. Some small-island countries and regions (theRepublic of the Marshall Islands, the Federated Statesof Micronesia, Tuvalu, the Republic of Kiribati, andFrench Polynesia in the Pacific, and the Republic ofMaldives in the Indian Ocean) consist fully or mostlyof atolls. Many atolls are also distributed around
Southeast Asia and in the South China Sea (e.g., theSpratly Islands), yet we have little information onthem.
Islands distributed on atolls are called atoll
islands (other terminologies for them are reefislands, atoll-reef islands, motu and cays). Since thesurface of reef flats only reaches low tide level,islands above high tide level are formed from bioclastic sand thrown up onto the reef flats, from©2005 AIRIES2H. KAYANNE et al.

Fig. 1 Map of Kwajalein Atoll.

Fig. 2 Map of Wake Island.

Fig. 3 World distribution of coral reefs with major categories of reef landforms.
Blue dots show atolls. Prepared by H. Shimazaki from ReefBase.

remnants of an emerged reef, or by a composite
process of both. The elevation of most of the islands
is one to two meters. More than 500 thousandpeople live on atoll islands. Some atoll islands (e.g.,Majuro Atoll in the Republic of the MarshallIslands and Funafuti Atoll in Tuvalu) are densely
populated and urbanized (Fig. 4). Residences andinfrastructure extend across these small, lowislands.

2. Geomorphology of Atoll Islands and Their
Submergence due to Rising Sea Levels
Since atoll islands are low, flat lands with amaximum altitude of one to two meters, they bear alimited amount of resources. Therefore, their vulnerability to environmental stresses is extremely
high. Among various threats to atoll islands, submergence due to rising sea levels induced by global
warming is the most serious, as it leads to loss ofnational land. The predicted rise in sea levels in the
21st century ranges from 10 to 90 cm with a medianFig. 4 Aerial view of Uliga Island, easternside of Majuro Atoll.
Photo by H. Yamano.

Sustainable Land Management of Atoll Islands

estimate of 40 cm (Fig. 5). The amount of this riseis crucial with regard to maintenance of island
landforms. At present, high-energy ocean swells
break mainly at the algal ridge, the seaward rise on
the reef flat (Fig. 6; Uliga Island in Majuro Atoll).
However, a 65 cm rise in sea level (upper level ofprediction) will raise the mean sea level to thepresent high water level, and ocean swells will
break directly onto the shore.
Against the backdrop of submergence, intensive
international concern has been elicited, and researchon possible responses of atoll islands to future sea

3level rises has been conducted mainly from an engineering point of view. However, formation of atoll
islands is regulated not only by physical but also by
ecological processes (Fig. 7). Yamano et al. (2005a)
reviewed the role of ecological process in detail. In
this introduction, we will raise two points.
Firstly, the source of sand constituting the islands
is calcifying organisms. Corals and foraminifera are
two major contributors of sand together with associated creatures, including calcareous algae, mollusks,echinoderms, and others. At Laura Island in Majuro
Atoll, the atoll island landform is divided into coral

Fig. 5 Projected curves of predicted sea level rise in the 21st century from the ‘IPCC
Third Report.’

Fig. 6 Schematic diagram of effect of sea level rise at Uliga Island, Majuro Atoll.

4H. KAYANNE et al.

reef flat, storm ridge, central depression and beachridge from ocean to lagoon (Fig. 8). This geomorphological zonation is generally applicable to otheratoll islands as well. The storm ridge is composed ofcoral boulders with diameters of several tens of centimeters. They are thrown up on the ocean side of theislands during heavy storms. The ridge forms thehighest elevation, up to 4 m in many atoll islands. The
beach ridge along the lagoon coast forms the otherhigh ridge. This ridge is composed of sand-sized calcium carbonate fragments of coral, foraminifera andother organisms.
Secondly, coral reefs on the ocean side of theislands act as a natural breakwater and provide bioclastic materials. If a coral reef is healthy, it has anupward growth potential of as much as 40 cm/100years. This potential rate matches the median predicted value of sea level rise. Thus a coral reef has apotential to keep up with rising sea levels to maintain its function of a natural breakwater and sediment source. However, global warming induces
frequent bleaching of corals, which degrades thereef potential, and the breakwater function is alsodegraded.
The formation of atoll islands is closely related tocoral reef formation from a geological point of view.
The coral reef flat was formed 3,500 years ago in
Majuro Atoll, and served as a basis for atoll islands.
The core of the atoll islands was formed 2,000 years
ago firstly at the central depression over several
decades in response to slight lowering of sea levels.
Then, the island extended lagoonward to form thebeach ridge. Occasionally, storms piled up coral boulders on the storm ridge along the ocean side of theisland.

Coral reef/algal ridge

Beadrock

Storm ridge

Fig. 7 Function of ecology in atoll island landform formation.

Fig. 8 Cross traverse and zonation of an atoll island at Laura Island, Majuro Atoll.

Sustainable Land Management of Atoll Islands

3. Function of Traditional Human Management
Traditionally, the resident people on atoll islands
have acted to maintain island landforms through preservation and management of vegetation (Fig. 9). Manyspecies of plants (taro, pulaka, banana, breadfruit,coco trees, pandanus, sugarcane) were introduced toatoll islands by people for their use as food and architectural materials. They implemented special protection and management strategies. Island vegetation has
served not only as various resources but also for maintaining soil and landforms. Roots of plants act tostabilize landforms. In particular, coastal vegetation ismost important for the protection of beaches. Knowing their functions, people have planted and protected
them to prevent costal erosion.

5However, traditional management systems collapsed in the wake of modernization and urbanization.
Since the introduction of the copra economy, island
landscapes changed to one of copra monoculture. The
expansion of coco forests led to loss of other plant
species. In the 1980s, the price of copra declined andtransportation costs increased. As a result, copra production declined and ill-maintained coco forests often
became overcrowded. Authorities or bureaucrats haveoften replaced traditional leaders. Agroforestry management has become difficult because of changes in
the human population structure, progressive depopulation, and changes in social politics. As a result, thevegetation on many Pacific atolls has been devastated.
In urban areas, coastal vegetation has been replacedby dumping sites (Fig. 10).
In addition, urbanization of atoll islands degrades

Fig. 9 Human function in atoll island landform maintenance.

Fig. 10 Dumping site along the storm ridge at Uliga Island, Majuro Atoll.

6H. KAYANNE et al.

coral reef health, which then reduces the upward
growth potential of the reefs and their biological function of sediment production. Calcium carbonate production, which provides sand to the island, is reduced
to less than half the values on a reef flat in an urbanized area. Degradation of the coral reef community
results in a reduced rate of sand formation andseverely detracts from sustainability of the island
landform.

4. Compound Threats and Sustainable Land
Management of Atoll Islands
Threats to atoll island landforms are complex,
not as simple as ‘submergence due to rising sea levels.’ The looming crisis to the atoll islands is thus acomposite of global and local stresses. In naturalprocesses, atoll islands are maintained by biologicalsand production, which is transported physically bywaves and coastal currents (Fig. 11). Coral reefs

form a natural breakwater to protect islands fromocean swells. Traditionally, human management
systems acted to maintain landforms. Sea level rises
induced by global warming will lead to submergence of atoll islands as a direct consequence (Fig.
12). In addition, submergence of coral reefs leads toloss of their breakwater function. Global warming
results in bleaching of corals, which degrades thepotential of upward growth and production of coral
reefs. Socio-economic changes increase humanstress on coral reefs, leading to their degradation.
Collapse of traditional management systems forisland vegetation will lead to collapse of theirmaintenance function of landform.
For sustainable utilization and development ofatoll islands, it is fundamental to evaluate the interaction between natural and human processes
through interdisciplinary research among geomorphology, anthropology and coastal engineering. In
2002, we started a feasibility study on atoll island

Fig. 11 Natural process of atoll island formation with traditional function of a human management system.

Fig. 12 Compound threats to atoll islands.

Sustainable Land Management of Atoll Islands

formation processes followed by our main researchon ‘Sustainable Land Management in Atoll Island
Countries’ from 2003 to 2005 funded by the Ministry of the Envrionment, Japan.
First, we classified atoll islands in relation to determining factors of atoll island formation and selected
representative atolls for intensive field surveys basedon this classification: Majuro Atoll in the MarshallIslands, and Funafuti Atoll in the Tuvalu Islands. In
this issue of Global Environmental Research, someresults obtained so far mainly from the research inMajuro Atoll are included. Yamano et al. (2005a) present an overview of the dynamics of atoll islands fromgeological, physical and ecological perspectives. Sediment transport along the lagoon coast is analyzed
from an engineering point of view by Yokoki et al.
(2005). On the other hand, Yamaguchi et al. (2005) reveal the settlement history at Majuro from archaeological point of view, and compare them with geomorphological development history of atoll island landforms. To generalize our field survey results, mappingand GIS technologies are necessary, which are shownin Yamano et al. (2005b) and Shimazaki et al. (2005).
The ultimate goal of our research is to establish adiagnosis of the present status and future response ofatoll islands to environmental changes. This researchaims to establish an ‘atoll island model’ to predict
their landform changes in response to future sea level
rises from geomorphological, ecological and coastal
engineering points of view. Another objective is tore-evaluate traditional systems of human management

7of island landforms and vegetation in effective utilization of resources and land. Based on the resulting
evaluation, we will propose appropriate adaptation
strategies to global changes. Remote sensing and GIS
will provide effective tools for extending the results
obtained in model fields to other atoll islands in general.
References
Shimazaki, H., H. Yamano, H. Yokoki, T. Yamaguchi, M.
Chikamori, M. Tamura and H. Kayanne (2005) Geographic
database on the natural and socioeconomic conditions of reefisland. Global Environmental Research, 9(1): 47-55.
Yamaguchi, T., H. Kayanne, H. Yamano, Y. Najima, M.
Chikamori and H. Yokoki (2005) Excavation ofpit-agriculture landscape on Majuro Atoll, Marshall Islands,
and its implications. Global Environmental Research, 9(1):27-36.
Yamano, H., H. Kayanne and M. Chikamori (2005a) An overview of the nature and dynamics of reef islands. Global Environmental Research, 9(1): 9-20.
Yamano, H., H. Shimazaki, H. Kayanne, H. Yokoki, T.
Yamaguchi, M. Chikamori, M. Tamura, T. Murase, Y. Suzui,K. Itou, M. Hirose, S. Sano, H. Takagi, M. Watanabe, F.
Akimoto, S. Watanabe, S. Yoshii, A. Ishoda, N. Leeders andW. Forstreuter (2005b) Efforts to generate maps of atollcountries. Global Environmental Research, 9(1): 37-46.
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Ando. H. Shimazaki, T. Yamaguchi, M. Chikamori, A.
Ishoda and H. Takagi (2005) Comparison between longshore
sediment transport due to waves and long-term shorelinechange in Majuro Atoll, Marshall Islands. Global Environmental Research, 9(1): 21-26.

(Received 19 May 2005, Accepted 30 May 2005)