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The inextricable links between climate change and sustainable development have been increasingly recognised over the past decade. In 2007, the Intergovernmental Panel on Climate Change (IPCC)1 concluded with very high confidence that climate change would impede the ability of many nations to achieve sustainable development by mid-century and become a security risk that would steadily intensify, particularly under greater warming scenarios. Article 4.8 of the United Nations Framework Convention on Climate Change (UNFCCC) lists several groups of countries that merit particular consideration for assistance to adapt to climate change “especially: (a) small island countries, (b) countries with low-lying coastal areas, c) countries with areas prone to natural disasters.” Small Island Developing States (SIDS) have characteristics which make them particularly vulnerable to the effects of climate change, sea level rise (SLR) and extreme events, including: relative isolation, small land masses, concentrations of population and infrastructure in coastal areas, limited economic base and dependency on natural resources, combined with limited financial, technical and institutional capacity for adaptation.2

The nations of CARICOM16 in the Caribbean together with Pacific island countries contribute less than 1% to global greenhouse gas (GHG) emissions (approx. 0.33%17 and 0.03%18 respectively), yet these countries are expected to be among the earliest and most impacted by climate change in the coming decades and are least able to adapt to climate change impacts. These nations’ relative isolation, small land masses, their concentrations of population and infrastructure in coastal areas, limited economic base and dependency on natural resources, combined with limited financial, technical and institutional capacity all exacerbates their vulnerability to extreme events and climate change impacts. Stabilising global GHG emissions and obtaining greater support for adaptation strategies are fundamental priorities for the Caribbean Basin and Pacific island countries. CARICOM leaders recently unveiled their collective position that global warming should be held to no more than 1.5°C19 and continue to develop a Climate Change Strategic Plan. The Pacific island countries have expressed their priorities for addressing climate change regionally through the Pacific Leaders’ Call to Action on Climate Change20 and the Pacific Islands Framework for Action on Climate Change 2006-2015.21

The lagoon of Tarawa harbors the richest benthos documented for any Pacific atoll. The biota is strongly influenced by its setting in the equatorial upwelling zone and the unusual geomorphology of the atoll, with a submerged western rim, but largely closed and islet-strewn eastern and southern sides. As the metropolitan center of the Republic of Kiribati, Tarawa also has the largest human population of any Pacific atoll. These three attributes impose a strong influence on all aspects of the lagoon. The high regional productivity supports unusually high population densities of heterotrophic mollusks and irregular echinoids for an "open" atoll. The dense human population on the atoll relics largely on marine resources for its protein needs. The lagoonal sand flat harbors dense and diverse mollusk communities, particularly in seagrass beds. These communities support an intensive subsistence fishery with an annual harvest of ca. 1,000 tons in South Tarawa. Much of the available biomass of the two preferred species, the blood cockle Anadara uropigimelana (te bun) and the small conch Strombus luhuanus (te nouo), is taken. Both the seagrass and shellfish beds appear to have expanded considerably in the past 50 years, likely as a result of nutrient enrichment from the rapidly growing human population. Dense mollusk communities along the southeastern lagoon slope at 2-8 m depth support an intensive commercial fishery that harvests approximately 1,000 tons of Anadara per year, again representing much of the available production. Three species of irregular echinoids are conspicuously abundant on the floor of the eastern lagoon, with combined densities > 100 m-2 in the muddy facies of the inner lagoon. All aspects of the benthos follow a marked west-to-east and north-to-south zonation, reflecting the one-sided exchange of oceanic waters along the western atoll rim. While mollusk and echinoid biomass increases southeastward, coral diversity and cover decreases in that direction.

The purpose of the present study is to: 1/ list the presently known heterodont bivalve fauna of the Cook Islands, 2/ document the habitat specificity of the species involved in as much detail as possible, and 3/ investigate the correlation between a species' habitat specificity and its distribution among the various islands. While several studies have been done on the molluscan fauna of inner reef environments on Pacific islands (though bivalves are often neglected), there has been little work on the fauna of the outer reef slope. An important part of this study involved documenting the bivalve species living on this slope, and thus a large portion of my survey was carried out there.