Cover Image
close this bookAgroforestry in the Pacific Islands: Systems for Sustainability (UNU, 1993, 297 pages)
close this folder2 Pacific Island agroforestry: Functional and utilitarian diversity
View the documentIntegration and sustainability
View the documentDiversity of function
View the documentBases for innovation and sustainability
View the documentAgroforestry and national development goals
View the documentExisting models and the need for appropriate innovation

Diversity of function

In terms of the more specific attributes of individual Pacific agroforestry systems, table 2 shows the many functions of these systems as well as the value of the individual arboreal components. Although modern resource developers see economic value and, possibly, even ecological, recreational, or nutritional value in native forests, in silvicultural tree plantings, in plantations of coconut, oil-palm, cocoa, coffee, or banana, and in orchards of orange, avocado, or macadamia, it is clear that Pacific Island agroforesters perceived arboreal resources to be far more pervasive in the landscape and still more multi-purposeful .

To emphasize the variety of arboreal functions in Pacific Island agrosilvicultural systems, we provide the following examples from the immense list possible.


Shade provides valuable protection to humans, plants, and animals, especially in savannas and in highly reflective low-lying coral island and lagoonal environments. Sunburn can be very severe in the tropical Pacific; solar-induced skin cancer is common. Trees provide not only a protective habitat that is open to cooling breezes but also materials for the production of almost all locally-produced headgear and structures used to protect Pacific fisherfolk and agroforesters and their animals and shade-loving plants against the sun's rays.

Protection from natural calamities

Damage from wind, salt spray, erosion, and flood are increased when forests are removed. This was evidenced in 1982 in Tonga by the comparatively minor damage to crops by Isaac in areas with even small groves of trees. This worst hurricane in Tonga's recorded history caused damage estimated at T$8 milion (aprox. US$9 milion) to crops and livestock alone (Thaman 1982a)

Table 2 Ecological and cultural functions and uses of trees in agroforestry systems in the Pacific Islands, based on fieldwork in Papua New Guinea, the Solomon Islands, Vanuatu, Fiji, Rotuma, Tonga, Western Samoa, Kiribati, and Nauru comparatively minor damage to crops by hurricane Isaac in areas with even small groves of trees. This worst hurricane in Tonga's recorded history caused damage estimated at T$8 million (approximately US$9 million) to crops and livestock alone (Thaman 1982a).

Shade Soil improvement Animal/plant habitats
Erosion control Frost protection Flood/runoff control
Wind protection Wild animal food Weed/disease control
Timber (commercial) Broom Prop or nurse plants
Timber (subsistence) Wrapping materials Staple foods
Fuel wood Abrasive Supplementary foods
Boat building (canoes) Illumination/torches Wild/snack/emergency
Sails Insulation foods
Tools Decoration Spices/sauces
Weapons/hunting Body ornamention Teas/coffee
Containers Cordage/lashing Non-alcoholic beverages
Wood carving Glues/adhesives Alcoholic beverages
Handicrafts Caulking Stimulants
Fishing equipment Fibre/fabric Narcotics
Floats Dyes Masticants
Toys Plaited ware Meat tenderizer
Switch for children/ Hats Preservatives
discipline Mats Medicines
Brush/paint brush Baskets Aphrodisiacs
Musical instruments Commercial/export Fertility control
Cages/roosts products Abortificants
Tannin Ritual exchange Scents/perfumes
Rubber Poisons Recreation
Oils Insect repellents Magico-religious
Toothbrush Deodorants Totems
Toilet paper Embalming corpses Subjects of mythology
Fire making Lovemaking sites Secret meeting sites

Deforestation commonly leads to accelerated erosion, and such degradation is ubiquitous in all high-island groups. Mangrove forests stabilize tidal-zone soil and reduce the impact of storm surge and salt spray. Trees also reflect terrestrial radiation and may provide some protection from frost to garden-edge crops at higher elevations in the Papua New Guinean highlands. It has even been suggested that pro grammes of coastal reforestation and agroforestry-based coastal reclamation, based on indigenous, salt- and wind-resistant trees and plants, could be one of the most effective strategies for addressing both the predicted short- and long-term effects of global warming such as increasing storminess, coastal erosion, and soil deterioration; declining fisheries and aquacultural yields; and decreasing soil fertility (Thaman 1989b).

Soil improvement

Natural soil improvement is another benefit provided by trees, especially given the high cost of fossil-fuel-dependent inorganic fertilizers and concern as to the detrimental impact on soil of long-term use of such fertilizers (Commoner 1971). Alioizia and Casuarina spp. are known by scientists and Papua New Guinean tribal farmers alike to enrich the soil for shifting gardens; as the Papua New Guineans say, such trees serve as a "garden mother" (Clarke 1965). Koka (Bischofia javanica), which is also believed to enhance soil fertility, is one of the most commonly protected trees in fallow areas in both Tonga and the wet and intermediate zones in Fiji. The extensive spread of the nitrogenfixing Middle American tree Leucaena leucocephala in many Pacific islands provides a recent example of this function (National Academy of Sciences 1977).

Forests and trees as habitats

Bird extinctions have been common on Pacific islands, and now many of the world's rarest or most threatened birds (the world's two rarest birds are the Mariana's mallard and the Kauai o'o of Hawaii) are found on Pacific islands. The past and threatened extinctions seem to be primarily the result of habitat elimination through deforestation (Dahl 1980; King 1981). Forest removal is also responsible, along with predation by profiteering collectors, for the endangerment of the worldrenowned birds of paradise and giant birdwing butterflies of Papua New Guinea. Without the recent introduction of protective legislation and butterfly-farming schemes, including the planting of host tree species, these valuable cultural, economic, and scientific resources would be lost (Pyle 1981).

Because deforestation may destroy the habitats of insects, birds, and other vertebrates that prey on crop pests, the process of forest loss may limit the potential for implementing integrated pest management programmes designed to minimize reliance on dangerous herbicides and pesticides (Bottrell 1978).

Timber, construction, and handicraft materials

Commercial timber operations supply local construction needs throughout the Pacific as well as generating significant amounts of foreign exchange in Papua New Guinea, the Solomon Islands, Fiji, and Western Samoa. Trees are also important in the informal sector of most countries for house construction, fencing, boat building, tool making, weaponry, making containers, and fishing gear (table 2). The coconut palm provides a whole storehouse of materials for house building, mat making, containers, fish traps (roots), and an array of handicrafts. The breadfruit for many islands is another tree of life, used for medicine, food parcelling, mulching, and canoe making. Bamboo contributes fishing poles, fencing, housing containers, and rafts. Many native species- e.g., Intsia bijuga, Cordia subcordata, and Thespesia populnea - are favoured for wood carving, but are now in short supply in Fiji and Tonga because of overexploitation. With the decline in these species, the introduced raintree (Samanea saman) has taken on increasing importance for making the traditionally-important kava bowl (tanoa in Fiji or kumete in Tonga).

Food resources

The nutritional importance throughout the Pacific of staple foods from trees such as coconut, breadfruit, bananas, sago palm, and Pandanus spp., along with a wide range of supplementary foods, snacks, or famine foods from other trees, has been widely stressed elsewhere and needs no further mention (Coyne 1984; Parkinson 1982; Rody 1982; Thaman 1979, 1982b, 1982c, 1983a, 1985b; Yen 1980a). Supplementary foods, snacks, and wild foods are described by Thaman (1975, 1976/77, 1982b) for Tonga and other Pacific islands and by Clarke (1965, 1971) for a highland Papua New Guinean community. Powell (1976a) provides a comprehensive coverage of wild foods and other important aspects of ethnobotany for the island of New Guinea.

Although many tree foods are energy-rich in carbohydrates and/or vegetable fats, it is in other nutritional essentials that they often excel compared with the ubiquitous root-crop staples and other annual nonarboreal plants. For example: mango, papaya, and some Panda nus spp. are excellent sources of provitamin A; Canarium spp., Inocarpus fagifer, and avocado (Persea americana) provide Bcomplex vitamins; and guava, mango, papaya, and Citrus spp. are rich in vitamin C. Most seeds or green leaves (for instance, from Ficus spp., Gnetum gnemon, which also provides edible seeds, and Moringa oleifera) are good sources of plant protein and a range of other micronutrients necessary for optimum health (Leung et al. 1972; Miller 1927; Miller et al. 1965; Murai et al. 1958; Thaman 1982c, 1983a). Moreover, all foods from trees and associated agroforestry-system ground crops are rich in fibre, which is essential to good health, but which is noticeably lacking in highly processed foods of urban diets (Coyne 1984; Thaman 1983a).

Spices and sauces from tree products can also be of great nutritional importance. Coconut cream or milk is used very widely in cooking, and local variants of the Rotuman taroro or Samoan sami lolo (concoctions of sea water aged or fermented with coconut flesh, often with chili peppers, in a coconut nut) enhance local cuisines. The sauce from Pandanus conoideus syncarps provides vitamin-A precursors and vegetable oil, nutritionally important additions to highland New Guinean diets. Indian cooking in Fiji utilizes tamarinds for chutney, the "curry leaf" (Murraya koenigii), a wide range of pickled fruits (achar), and many other tree products.

Trees are also important sources of food and fodder for domesticated animals. Pisonia grandis leaves, for example, are used as pig feed in Tonga; avocados are fare for pigs in the Cook Islands; Leucaena leaves and pods are used widely for goats, pigs, and cattle; and coconuts and papaya are abundant and important animal foods throughout most of the Pacific.

Wild food and other valuable products are lost to subsistence communities when the diverse plants and animals that supplied them disappear along with the forest that served as their habitats (Clarke 1965, 1971; Thaman 1982b). Destruction of the Calophyllum inophyllum forest and stands of Pisonia grandis on Nauru's central plateau, as a result of opencast phosphate mining, has eliminated roosting areas for the noddy bird, which is of considerable social and dietary importance to the Nauruan people (Manner et al. 1984, 1985). Deforestation has also restricted the habitats for wallabies and the valued cassowary bird of Papua New Guinea, and a great number of vertebrate and non-vertebrate wild foods that contribute significantly to the dietary well-being of many Pacific Islanders, particularly in the interior of large continental islands.

Mangrove ecosystems, which can be considered as a kind of outrider to agroforestry systems, contribute, either directly or indirectly through primary and secondary productivity, to the nutritional requirements of many marine species used as food by humans (Watling 1985). Research in Fiji has shown that over 60 per cent of commercially-important species are associated with mangroves at some stage in their life cycle (Lal et al. 1983), whereas more rigorous research gives figures of 67 and 80 per cent for eastern Australia and Florida (Walling 1985). Destruction and "reclamation" of such resources undoubtedly have deleterious effects on fisheries yields, with studies in the Malacca Straits indicating that mangrove clearing for industrial expansion led to a substantial drop in catches per effort (Khoo 1976). Baines (1979) argues that mangrove removal can lead to yield declines in offshore fisheries of 50-80 per cent.

Medicinal value

The arboreal pharmacopoeia is widely known and valued by modern science and industry as well as by local inhabitants. As everywhere in the tropics, all parts of the Pacific possess medicine-producing trees. For example, Nauru, which has an impoverished flora (some 49 indigenous species including non-trees), has 24 tree species with medicinal uses. Similarly, of 93 medicinal plant species found in urban gardens in Fiji, Tonga, Kiribati, and Nauru, 55 per cent (51) were trees and another 10 were woody shrubs (Thaman 1987).

Love potions and perfumes

More for pleasure than curing are love potions or aphrodisiacs and perfumes from trees. Guettarda speciosa, a coastal tree common in home gardens in Nauru and Kiribati, has flowers that when boiled in water produce a liquid that a woman can drink to "make a man go crazy" when she sweats. Perfumes or scents such as sandalwood are well known outside the Pacific and have drawn foreign exploiters from early European times to the present. In the late 1970s the profligate shipping of sandalwood from Tonga to Singapore and Hong Kong was stopped because of public outcry. Less cosmopolitan fragrances are derived from Cananga odorata and other scenting agents that are put into coconut oil from trees such as Pimenta, Plumeria, Gardenia spp., Parinari glaberrima, Aglaia saltatorum, Fagraea berteriana, and Calophyllum inophyllum. In Tonga, for example, there are over 50 species of sacred or fragrant plants, known as 'akau kakala, that are central to the spiritual and economic fabric of Tongan society and that are planted or protected as integral components of Tongan agroforestry.

Other uses

Wrapping materials include coconut leaves, leaves of Artocarpus altilis, Musa cultivars, Hibiscus tiliaceus, and Macaranga spp. Other leaves, notably Ficus spp., serve as effective abrasives. Dyes are derived from many sources, e.g., Bischofia javanica (a major brown dye for tape), Bruguiera spp. and Aleurites moluccana (black), Morinda citrifolia (yellow and red), and Bixa orellana (red).

These few examples from the list in table 2 show the utilitarian diversity and the economic and cultural value derived from trees and agroforestry in the Pacific - values that are rarely acknowledged in planning or project documents but that would be costly, difficult, or impossible to replace with imported substitutes. The elimination of such utilitarian and cultural diversity can only serve to lock Pacific societies more tightly into economic and cultural dependency.