Cover Image
close this bookAgroforestry in the Pacific Islands: Systems for Sustainability (UNU, 1993, 297 pages)
close this folder1 Introduction
View the documentContext of the study
View the documentGeographical background
View the documentDefinition of terms
View the documentDeforestation and agrodeforestation in the Pacific
View the documentOrganization of the study

Geographical background

The Pacific Islands are, for the purposes of this study, defined as the islands of Melanesia, Micronesia, and Polynesia (excluding Hawaii and New Zealand) (see map p. 5). The study area includes the large continental island of New Guinea in the west and extends to the small atolls and recent volcanic islands of the central and eastern Pacific, where traditional agroforestry systems remain common in unchanged or only slightly modified forms. Some of the political units are single islands rather than island groups (e.g., Nine and Nauru), or territories rather than independent countries (e.g., New Caledonia, French Polynesia, American Samoa, and Guam). For simplicity's sake, they will be included in discussion of "groups" or "countries."

The Pacific islands

The study area includes a diversity of island types:

  1. Continental islands, such as New Guinea and New Caledonia, which are composed of geologically-ancient sedimentary, metamorphic, and igneous rocks of continental origin.
  2. Andesitic-arc islands, such as most of the islands of the Solomon Islands, Vanuatu, Fiji, Guam, and the Northern Marianas, as well asthe eastern islands of Papua New Guinea (e.g., Manus, New Britain, and Bougainville) and the more recent volcanic islands of Tonga (e.g., Niuatoputapu, Niuafo'ou, Kao, and Tofua). Andesitic-arc islands have been formed by recent andesitic volcanic activity in proximity to the subduction zone (previously, but now inappropriately, referred to as the Andesite Line), where the newer crust of the Pacific Plate and the older crust of the Indo-Australian Plate come together, with one being forced (subducted) under the other.
  3. Basaltic volcanic ("hot-spot") islands, which are high oceanic islands such as the Samoas, the Cook Islands, Tahiti in French Polynesia, the Hawaiian Islands, and Pohnpei (Ponape) and Kosrae in the Federated States of Micronesia. Hot-spot islands have been formed as the result of the extrusion of magma through cracks or rifts in the Pacific Plate as it moves over "hot spots" in the Earth's mantle.
  4. Raised limestone islands such as Nauru and Nine, the islands of Vatulele in Fiji, Aniwa in Vanuatu, Ouvea in the Loyalty Islands of New Caledonia, most of the Tongan group, and portions of Mangaia and Atiu in the southern Cook Islands and Vanuabalavu in Fiji. These islands, formed of old-reef and foraminiferous limestone, have experienced considerable uplift relative to sea level.
  5. Coral atolls is a term that technically refers to the roughly circu lar coral-reef structures at, or just below, or slightly above, sea-level that usually support scattered reef islets (motu) and that surround a central lagoon. Most of the islands in the Marshall Islands, Kiribati, Tokelau, and the Tuamotus in French Polynesia are atolls. Often included in the category are reef islets or "table reefs," such as Arorae and Tamana in Kiribati and Nukulaelae in Tuvalu, which have no lagoons and should probably be categorized as raised coral-limestone islands. Reef islets would also include islets on barrier reefs surrounding larger islands, but clearly separated from the main island by a lagoon. Similarly, some barrier reefs and associated reef islets, such as those around the central volcanic peaks and lagoons of the islands of Aitutaki in the Cook Islands and Bora Bora in French Polynesia, take the form of atolls. These islands are commonly referred to as "almost atolls" because remnants of the volcanic peak that forms the foundation of all atolls still remain emergent above sealevel in the central lagoon.

It must be stressed that, just as there are continental or andesitic islands very far from continental shores in the Pacific (e.g., Easter Island), there is also basaltic volcanic activity close to subduction zones that cannot be reconciled with the hot-spot model and remains largely unexplained (e.g., Taveuni in Fiji). Similarly, raised limestone islands, atolls, and reef islets can be found on both sides of the subduction zone, thus adding considerable ecosystemic and environmental diversity, with most island groups including more than one island type (table 1).

There is also great geographical and demographic diversity among the islands. Easter Island, Guam, Kosrae, Nauru, and Niue consist of a single small island; Fiji, Tonga, French Polynesia, and Hawaii consist of hundreds of large and small, widely dispersed islands; Papua New Guinea and Irian Jaya share the very large, high continental island of New Guinea, and both include many smaller offshore islands. Total land areas vary from 10 to 26 sq km for groups of low-lying, coral-limestone islands like Tokelau and Tuvalu to over 400,000 sq km for the continental island areas of Irian Jaya and Papua New Guinea (Thaman 1988a).

Population densities for entire groups range from just over 1 person per sq km for the Galapagos and Pitcairn Island and 2.5 for Irian Jaya, to almost 300 or more for Nauru, Truk, and Tuvalu. If the "most populous islands" are considered, the figures jump to over 100 persons per sq km for four islands, and over 200 for three islands;

Table I Types of islands up selected island nations and territories of the tropical Pacific Ocean. (Some individual islands may be composite, combining more than OK island type) and are 421 for Koror in Palau, 757 for Funafuti in Tuvalu, 1,179 for Majuro in the Marshall Islands, and 2,190 for Tarawa in Kiribati. The estimated population for Betio Islet of Tarawa atoll is expected to reach 34,066 by 1993, which will give it a population density of 4,705 per sq km, thus rivalling the population densities of Hong Kong (Carter 1984, 231). If we consider Ebeye, one of some 90 islets of Kwajalein Atoll in the Marshall Islands, to which people have been relocated by the US military to free the atoll's lagoon for intercontinental ballistic-missile testing, the population density sky-rockets to 25,000 per sq km (Keju and Johnson 1982)!


Nation or territory Continental Andesitic arc High basaltic Raised limestone Coral Atoll
Irian Jaya + +   +  
Papua New Guinea + +   + +
Torres Strait + +   +  
New Caledonia + +   + +
Solomon Islands   +   + +
Vanuatu   +   + +
Fiji   + + + +
Tonga   +   +  
Wallis and Futuna     + +  
Western Samoa     +    
American Samoa     +   +
Nine       +  
Tuvalu       + +
Tokelau         +
Cook Islands     + + +
French Polynesia     + + +
Pitcairn Island     +   +
Hawaii     +   +
Easter Island     +    
Galapagos Islands     +    
Palau       +  
Guam   +   +  
Northern Marianas   +      
Yap     +   +
Truk     +   +
Pohnpei     +   +
Kosrae     +    
Nauru       +  
Marshall Islands         +
Kiribati       + +

Sources: Personal observation; Carter 1981, 1984; Dahl 1980; Klee 1980b; Thaman 1988a.

This range of diversity in island types and population densities when combined with differences in climate, geological resources, topographical features, soil types, water availability, flora and fauna, and culture - goes a long way to explain the diversity of agroforestry systems found in the Pacific Islands. The more specific nature of the physical and biological resources of individual island ecosystems, and the extent to which they are currently protected or endangered by exploitation, have been comprehensively analysed by Arthur Dahl (1980) in his Regional Ecosystems Survey of the South Pacific Area, which contains descriptions and the conservation status of all marine and terrestrial ecosystems and physical and biological features or resources of particular ecological and cultural importance; as well as lists of rare, endemic, or endangered species; existing and proposed conservation legislation; and existing, proposed, and recommended reserves for each island group.

It is beyond the scope of this study to present such detailed information, although some of it will be considered in the case-studies of individual agroforestry systems. For detailed data on various aspects of island groups see Bakker (1977a, 1977b), Brookfield with Hart (1971), Carter (1981, 1984), Dahl (1980), Douglas and Douglas (1989), McArthur (1967), Thaman (1988e), Ward and Proctor (1980), and Winslow (1977).