At 63.8 million square miles (165.25 million square kilometers), the Pacific Ocean is the largest ocean in the world, covering approximately 33% of the Earth’s total surface . The vast ocean contains approximately 30,000 islands divided between the Polynesia, Melanesia, and Micronesia regions . Pacific RISA works only in Pacific Islands associated with the United States (U.S.-Affiliated Pacific Islands or USAPIs), which include the State of Hawaiʻi, the Territory of American Samoa, the Territory of Guam, the Commonwealth of the Northern Mariana Islands (CNMI), the Republic of Palau, the Republic of the Marshall Islands (RMI), and the Federated States of Micronesia (FSM). Irrespective of political boundaries, the islands of the Pacific have multiple associations and affiliations through regional organizations and cultural ties. Geographic remoteness is typical, and the associated costs of transport and shipping have a profound influence on island economies and societies. These commonalities further strengthen Pacific regional connections and approaches in dealing with environmental issues and climate change.
The islands differ geomorphologically, from low atolls, to raised limestone islands, to volcanic high islands with substantial topographic diversity. They differ climatically as well, from wet western equatorial islands to seasonal tradewind environments . Pacific Island landscapes and biodiversity are many and varied. Forested areas are still common in upland areas of high islands such as Hawai‘i, American Samoa, and Pohnpei and Kosrae States in the FSM. Mangrove forests fringe some islands, and form the breeding grounds for many valuable fish species and other marine life. Rich lagoons interlace other islands. Throughout the region, coral reefs are abundant and productive. In addition to hosting a wealth of marine life, the reefs also provide a natural form of coastal protection against storm wave and wind damage. Terrestrial resources of small-island states are generally limited. Oceanic islands have lower overall levels of biological diversity. Island species are much more likely to be endemic (found only on a single island or archipelago) and more susceptible to disruption by biological invasions and species loss .
The Pacific Islands are the home of an estimated 10,012,371 people in 2011 . Approximately 1.9 million people live in the US-Affiliated Pacific Islands, with close to 70% located in Hawai‘i. Subsistence and commercial fisheries, tourism, and subsistence and semi-subsistence agriculture contribute greatly to Pacific Island economies.
Traditionally the Pacific Islands have close cultural, economic, and spiritual relationships with the land and sea. Clans and lineages in local social organizations and chiefly systems persist in many islands. They have retained an especially influential role in planning and decision-making in the RMI, many islands in the FSM, and American Samoa. To be effective, environmental management in the islands relies on collaboration among various government and traditional decision-making authorities, each of which brings something unique to the process. Local and national decision-making and planning organizations are augmented by grassroots, regional, and international organizations. These organizations and institutional arrangements, if constructively engaged, can enhance the adaptive capacity and reduce the sensitivity of island coastal communities to climate change and variability .
Throughout the Pacific, islands vary greatly in geological, physical, and climatic features. The level of exposure and sensitivity to cyclones and to ENSO-related climatic variability is different from place to place. Nevertheless, characteristics such as limited land size, proneness to natural hazards, and external shocks enhance the vulnerability of all islands to climate variability and change. In most cases, small islands have low adaptive capacity, and adaptation costs are high relative to gross domestic product (GDP) . According to the fourth assessment of the International Panel of Climate Change (IPCC), the potential impacts of climate change and variability on small islands were presented as follows :
• Sea-level rise is expected to exacerbate inundation, storm surge, erosion and other coastal hazards, thus reducing the island size, threatening vital infrastructure, settlements, and facilities that support the livelihood of island communities.
• Limited water resources in small islands are especially vulnerable to future changes, and distribution of rainfall is likely to be seriously compromised.
• Increasing sea surface temperature, rising sea level, and growing ocean acidity are very likely to affect the health of coral reefs and other near shore, marine and coastal ecosystems. These impacts exacerbate non-climate change-related stresses on the systems.
• Changes in the occurrence and intensity of El Niño-Southern Oscillation (ENSO) events are likely to have severe impacts on commercial and artisanal fisheries. Forests on many small islands can easily be decimated by violent cyclones or storms, while increases in extreme events effect the adaptation capacity of the slow-regenerating forests.
• Sea-level rise, inundation, seawater intrusion into freshwater lenses, soil salinization, and decline in water supply are very likely to adversely impact coastal agriculture. Away from the coast, changes in extremes (e.g., flooding and drought) are likely to have a negative effect on agricultural production.
• Effects of climate change on tourism are likely to be direct and indirect, and largely negative. Sea-level rise and increased sea water temperature will cause accelerated beach erosion, degradation of coral reefs, and bleaching. In addition, a loss of cultural heritage from inundation and flooding reduces the amenity value for coastal users. Water shortages and increased incidence of vector-borne diseases may also deter tourists.
• There is growing concern that global climate change is likely to impact human health, mostly in adverse ways. Increasing incidence of diseases has been observed. Examples include malaria, dengue, filariasis, schistosomiasis, and food- and water-borne diseases.
Related Links Pacific Climate Information System (PaCIS) Pacific Islands Applied Geoscience Commission (SOPAC) Pacific Islands Global Ocean Observing System Pacific Islands Global Climate Observing System Secretariat of the Pacific Regional Environment Programme (SPREP) Pacific Climate Change Portal Secretariat of the Pacific Community (SPC) United Nations Framework Convention on Climate Change (UNFCCC) United Nations Development Programme (UNDP) Pacific Centre United Nations Environment Programme (UNEP) References  Wikipedia, Pacific Ocean, http://en.wikipedia.org/wiki/Pacific_Ocean, accessed September 14, 2012.  Secretariat of the Pacific Community, Statistics for Development, 2011 population & demographics indicators, http://www.spc.int/sdp/index.php?option=com_docman&task=doc_download&gid=344&Itemid=42&lang=en, accessed September 14, 2012.  Shea, E., G. Dolcemascolo, C.L. Anderson, A. Barnston, C.P. Guard, M.P. Hamnett, S.T. Kubota, N. Lewis J. Loschnigg, & G. Meehl. 2001. Preparing for a Changing Climate: The Consequences of Climate Variability and Change for Pacific Islands. Honolulu: East-West Center, http://www.eastwestcenter.org/publications/preparing-changing-climate-potential-consequences-climate-variability-and-change-execut, accessed September 14, 2012.  Mimura, N., L. Nurse, R.F. McLean, J. Agard, L. Briguglio, P. Lefale, R. Payet and G. Sem, 2007. “Small Islands”. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds. Cambridge, UK: Cambridge UniversityPress, 687-716. http://www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-chapter16.pdf, accessed September 14, 2012. Header image: A healthy tropical Pacific coral reef, Palmyra Atoll National Wildlife Refuge. (Source: J. Maragos, USFWS)