| Agroforestry in the Pacific Islands: Systems for Sustainability (1993) |
|10 Agroforestry in the Pacific Islands: Systems for sustainability|
The component trees
The case-studies in this book illustrate the richness of the existing heritage of polycultural agroforestry possessed by all Pacific societies, both rural and urban, both predominantly subsistence and strongly focused on cash-crop production. By definition, it is trees and tree-like species that are fundamental to these almost endlessly variable systems. If the existing systems are to be preserved and utilized in future agroforestry development, it is of course necessary to preserve the trees themselves as well as to have an inventory of information about them. Analysis of available information from the literature and field surveys has led to the identification of 419 cultivated and/or wild tree or tree-like species or groups of closely related species that are of widespread or localized economic, cultural, and ecological importance in Pacific Island rural and urban agroforestry systems. As these plants have already been shown to be useful components of local agroforestry systems, they merit consideration for future use, but to discuss here, or even to list, all 419 species or groups of species would be impractical as well as daunting to all but the most botanically-minded of readers. In place of that overload of information, we discuss here only a few arbitrarily selected details. In the Appendix, the characteristics and uses of 100 Pacific Island agroforestry trees are described more fully so as to provide the interested reader with a picture of the rich variety of species available.
Selection of agroforestry resources
Whether on high islands, with their often rich soils, varied habitats, and low population densities; on the harsh atolls almost without soil and short of water; or in home gardens in densely settled urban areas and monocultural rural agricultural areas, Pacific Islanders have selected for incorporation into their agroforestry systems a wide range of tree and tree-like species that meet their particular en vironmental and cultural needs. The use of these species is the cumulative result of a selection process that has occurred over thousands of years, beginning in the ancestral homelands of today's Pacific Islanders in SouthEast Asia and the archipelagic areas of Indonesia, the Philippines, and Papua New Guinea, whence valuable cultigens and accumulated knowledge of wild species were transferred to the smaller Pacific oceanic islands.
After they arrived, early settlers domesticated previously unknown indigenous species or else incorporated them as wild species into agroforestry systems prior to European contact (Yen 1990). Similarly, post-Europeancontact introductions, including food plants, timber trees, and ornamentals have been tested, selected, and incorporated into today's systems to such an extent that the undiscerning visitor or agricultural "expert," and many of the current generation of islanders, believe the introduced trees to be traditional or even indigenous. The integration has been carried to such an extent that the status of many species remains unclear as to whether they are local domesticates or indigenous plants, aboriginal introductions brought to the islands by successive waves of Pacific settlers, or early postEuropean-contact introductions.post-European-contact
Of the 419 agroforestry plants, approximately 329 are classified as large or small tree or tree-like species, whereas approximately 90 are smaller, more shrub-like perennials, which constitute common fixtures in Pacific Island agroforestry systems. The division into shrubs and trees is, of course, somewhat arbitrary because some species, depending on the environment, the variety, or cultivar, can be either shrubby or tree-like. For example, the species Hibiscus tiliaceus, Pipturus argenteus, and Vitex trifolia are all found as both shrubs and trees. Similarly, groups of highly variable, closely related species of the genera Leucosyke, Pandanus, Pittosporum, Psychotria, Solanum, and Timonius are all represented by both shrubs and trees.
A very limited sampling of shrubs and shrub-like species would include the indigenous, often wild, plants such as Acalypha insulana, Dodonaea viscosa, and Pemphis acidula. Important food or beverage plants in the "shrub" category include the bush hibiscus spinach (Hibiscus manihot); sugar cane, which, along with the related species with the edible inflorescence (Saccharum edule), forms tree-like stands in Pacific gardens; kava (Piper methysticum), the important social bev erage of Vanuatu, Fiji, Polynesia, and Pohnpei; betel pepper (Piper belle), which is cultivated in western Melanesia, high-island Micronesia, and by the Indian community of Fiji. Shrubby handicraft plants of a widespread importance include paper mulberry (Broussonetia papyrifera), which extends from the highlands of Papua New Guinea, where it is used in the production of string bags (bilum) and a wide array of loin cloths, to Polynesia, where it is used in the production of the ceremonially important tape cloth, an increasingly valuable source of cash income from the tourist industry; and a wide variety of Pandanus species or cultivars, whose leaves are used in plaited ware such as fine mats, thatching, hats, baskets, and other items of cultural and economic importance. The rattan palms (Calamus spp.) are important in Papua New Guinea for handicrafts and general construction. The introduced annatto (Bixa orellana) is widely planted for its seeds, which yield a red dye, and has been a minor smallholder export crop in Western Samoa.
"Protective" or magical plants, established in or around active garden areas to ward off evil spirits, include Cordyline fruticosa, Coleus scutellarioides, and Euphorbia fidjiana, which may be present only in Fiji and Tonga.
Origin or antiquity status
Of the 419 species, approximately 172 (41 per cent) are probably indigenous to most islands where they are found; 13 are probably aboriginal introductions; 40 either indigenous or aboriginal introductions; 147 (35 per cent) are recent post-European-contact introductions; 17 are indigenous in some areas but recent introductions in other areas; 17 are both aboriginal or recent depending on the area; and 13 are indigenous, aboriginal, or recent depending on the area. It is, however, extremely difficult to determine whether some species were indigenous or introduced by early settlers, and their status may be different in different areas. For example, Terminalia catappa may be both indigenous and/or an aboriginal introduction to some areas, whereas it is probably a recent introduction into Hawaii.
The 172 possibly indigenous species include plants from Pacific Island coastal strand forest, mangrove forest, marsh or riparian and indigenous lowland, and montane forest, as well as pioneer species common in fallow vegetation. All are important components of plots of relatively undisturbed vegetation bordering or included in agroforestry systems and are often deliberately protected or planted as in tegral components of rural gardens or plantations and urban gardens because of their cultural and ecological utility.
Of the more than 80 species that may be aboriginal introductions to at least some islands, the most widespread and culturally important species are food plants. These include the ubiquitous "tree-of-life" coconut palm, breadfruit, the many traditional banana and plantain cultivars, sago palm, edible pandanus cultivars, sugar cane, bush hibiscus spinach (Hibiscus manihot), and a variety of fruit and nut trees and other supplementary food crops.
Also, almost certainly aboriginal introductions to most areas were the important social masticant and beverage plants, betel-nut palm (Areca catechu) and betel pepper (Piper belle), kava (Piper methysticum); the important fibre and handicraft plants, paper mulberry (Broussonetia papyrifera) and a wide range of Pandanus species or cultivars; the candlenut (Aleurites moluccana) and the perfume tree (Cananga odorata), so highly valued for scenting coconut oil; and a wide range of other plants of cultural value for general construction and boat building, medicines, dyes, poisons, fibre, perfumes, decorations, magic, and other purposes.
The recent post-European-contact introductions include important longestablished food trees such as the papaya, mango, avocado, a range of Citrus species, guava, soursop, sweet sop, and three important commercial banana clones; the ubiquitous perennial chill) pepper; food trees of more localized importance, such as the jakfruit, tamarind, horseradish, or drumstick, tree (Moringa oleifera), and the Indian bay, or curry leaf (Murraya koenigii), all of particular importance to the Indian community of Fiji; and a wide range of fruit and nut trees of minor importance. (See the Appendix for further details on some of these plants.)
Recent introductions of commercial importance include tea, coffee, oilpalm, Para rubber, cocoa, and new, often high-yielding, cultivars or clones of plants such as the coconut palm, bananas, and citrus trees; the exotic timber species including Cordia alliodora, Eucalyptus deglupta, Caribbean pine (Pinus caribaea), and West Indian mahogany (Swietenia macrophylla); and a number of other species that are, or will be, important sources of income to some countries in the region.
Other recent introductions include the common bamboo, cotton, kapok, the neem tree (Azadirachta indica), allspice and bay rum tree (Pimenta doica and P. racemosa), and castor bean (Ricinus communis); a number of fastgrowing multi-purpose trees, most notably
Leucaena leucocephala, madre de cacao (Gliricidia septum), Pithecellobium dulce, Sesbania grandiflora, Erythrina spp., and Jatropha curcas; a wide range of exotic ornamental trees and shrubs, the most common including the orchid tree (Bauhinia spp.), bougainvillea, flowering cassias, poinciana, or flamboyant, banyans (Ficus spp.), gardenias, lantana (Lantana camara), Persian lilac, or China berry (Melia azedarach), mock orange (Murraya paniculata), the ubiquitous plumerias, or frangipanis, monkey-pod, or rain tree, and the African tulip tree; and a number of widely cultivated ornamentals, such as Acalypha amentacea, Codiaeum variegatum, Gardenia taitensis, Graptophyllum pictum, hedge panaxes (Polyscias spp.), and Pseuderanthemum spp. A number of palms, although recent introductions into the eastern parts of their range, are possibly indigenous to or even domesticates of Melanesia or Polynesia.
All 419 plants or groups of plants are found in the diverse agroforestry environments of either high islands or the larger limestone islands, with no species of widespread or major local importance confined to the atoll environment. Only 83 species (20 per cent) are commonly found on Pacific atolls, which reflects both the poverty of the indigenous and exotic floras on atolls as well as the critical importance of all agroforestry species that do succeed in growing on atolls. Of these 83 species, 30 are ubiquitous Pacific strand or mangrove species, 26 are introduced ornamentals, with the balance consisting of aboriginally introduced plants, recently introduced food plants, and a small number of recently introduced timber, fuel-wood, or other useful plants.
Of the 419 agroforestry plants, some 113 are found almost exclusively in a wild state, 127 are cultivated, and about 179 are both cultivated and wild. The 113 exclusively wild or uncultivated species are made up of indigenous coastal strand, mangrove, and inland-forest species commonly protected in forest stands. Also included are several pioneering species that, although not generally protected when clearing new garden plots, are encouraged through selective weeding and become dominant components of the young fallow forest.
The strictly cultivated species, on the other hand, are almost entirely exotic cultigens. These include major and minor fruit or food species, ornamentals, exotic timber or fuel-wood species, major and minor export crops, and a number of handicraft, medicinal, spiritual, and other multi-purpose species.
Species found both cultivated and in a wild state include a wide range of indigenous species, which are also deliberately cultivated, as well as cultigens, most of which are exotic, that have escaped or become naturalized and are seen to have significant cultural or ecological value. Among the most commonly cultivated indigenous species are a large number of ubiquitous coastal strand plants valued for their multi-purpose utility. Some trees indigenous to Melanesia in the genera Acacia, Agathis, Albiza, Araucaria, Endospermum, and Terminalia have been deliberately planted or experimented with as timber species for reforestation programmes.
Species that are both cultivated and either commonly naturalized or indigenous include food species such as coconut, breadfruit, sago palm, sugar cane, Saccharum edule, and Cordyline fruticosa. Other food trees in this category are Adenanthera pavonina, Barringtonia spp., Burkella obovata, Canarium spp., Castanospermum australe, Corynocarpus similis, Dracontomelon vitiense, edible figs (Ficus spp.), Finschia chloroxantha, Gnetum gnemon, Musa troglodytarum, Pangium edule, Pometia pinnata, and Syzygium malaccense. Other cultigens found wild are candlenut (Aleurites moluccana), betel-nut and betel pepper, perfume tree, or ylang ylang (Cananga odorata), Schizostachyam glaucifolium, Sida fallax, and Solanum uporo. Most of these species are commonly found in mature fallow forests, where they are either remnants of former cultivation or naturalized escapes or volunteers that have either been protected by agriculturalists or, in some cases, may have been components of the indigenous flora.
Recent post-European-contact introductions that have become most widely naturalized, commonly as escapees from cultivation, include the perennial chill) pepper, papaya, lantana, leucaena, and guava. Other commonly naturalized species include Acacia farnesiana, Brassaia actinophylla, Cassia alata, citrus trees, derris root, mango, Melia azedarach, and castor bean. There are others of more localized importance, many of which are either selfsown or have grown from seeds discarded by humans. Although growing wild, most of these species cannot be considered fully naturalized as they grow mostly in disturbed sites and are generally displaced by indigenous vegetation in mature fallow forests.
In terms of relative importance, 56 of the 419 species are considered to be of major agroforestry importance in many island groups in terms of abundance and/or ecological importance and cultural utility. These include:
Table 11 Tree or tree like species or groups of closeb related species of mqior agroforestry importance in certain localities and/or widespread supplementary ecological or cultural importance (See Appendix for detailed information on some of the species listed here)
|Acalypha amentacea vars.||Diospyros samoensis||Musa troglodytarum|
|Adenanthera pavonina||Diospyros spp.||Musa cultivars|
|Aglaia saltatorum||Dracontomelon vitiense||Myristica spp.|
|Aglaia spp.||Dysoxylum forsteri||Neisosperma|
|Albizia lebbeck||Elaeis guineensis||Nerium oleander|
|Alphitonia spp.||Flaeocarpus spp.||Pandanus conoideus|
|Alyxia spp.||Endospermum spp.||Pandanus dubius|
|Annona squamosa||Eucalyptus deglupta||Pandanus julianettii|
|Antiaris toxicaria||Eucalyptus spp.||Pangium edule|
|Araucaria cunninghamii||Euadia hortensis||Parinari glaberrima|
|Araucaria heterophylla||Euodia spp.||Pemphis acidula|
|Artocarpus heterophyllus||Ficus benjamina||Persea americana|
|Artocarpus mariannensis||Ficus copiosa||Phaleria spp.|
|Barringtonia asiatica||Ficus dammaropsis||Pinus caribaea|
|Barringtonia edulis||Ficus obliqua||Pisonia grandis|
|Bauhinia monandra||Ficus tinctoria||Planchonella spp.|
|Bougainvillea spp.||Ficus wassa||Plumeria obtusa|
|Burkella obovata||Ficus spp.||Polysciasfruticosa|
|Cajanus cajan||Garcinia sessilis||Polyscias scutellaria|
|Canarium indicum||Garcinia spp.||Prichardia pacifica|
|Canarium spp.||Cardenia jasminoides||Pterocarpus indicus|
|Cassia alata||Cardenia taitensis||Rhus taitensis|
|Cassiagrandis||Cliricidia sepium||Santalum spp.|
|Casuarina oligodon||Gnetum gnemon||Scaevola sericea|
|Cerbera manghas||Grewia crenata||Schizostachyum|
|Citrus aurantiifolia||Heliconia indica||glaucifolium|
|Citrus aurantium||Hernandia||Securinega flexuosa|
|Citrus grandis||nymphaeifolia||Sida fallax|
|Citrus limon||Homalanthus spp.||Solanum melongena|
|Codiaeum variegatum||lntsia bijuga||Spathodea campanulata|
|Coffea arabica||Ixora spp.||Sterculia spp.|
|Coffea canephora||Jatropha curcas||Swietenia macrophylla|
|Coleus scutellarioides||Kleinhovia hospita||Syzygium cumini|
|Commersonia bartramia||Lantana camara||Syzygium richii|
|Cordia alliodora||Lumnitzera littorea||Syzygium spp.|
|Cryptocarya spp.||Melaleuca leucadendra||Tamarindus indica|
|Cycas circinalis||malabathricum||Terminalia spp.|
|Decaspermum fruticosum||Metrosideros collina||Tournefortia argentea|
|Denrocnide spp.||Micromelum minutum||Trema spp.|
|Derris spp.||Moringa oleifera||Vitex spp.|
Also of major agroforestry importance, although not quite as widespread or as abundant in indigenous agroforestry systems, are another 125 species or groups of closely related species. These include:
If all the individual plants belonging to the over 400 species of agroforestry trees and shrubs should suddenly vanish, Pacific Island landscapes and life would be dramatically altered, and a near irreplaceable resource would have been lost. The manifold utility of the agroforestry species has been stressed throughout this book. They fulfil cultural, economic, and ecological functions, with the majority of species serving multiple purposes, as shown by a study of coastal species commonly found in Pacific Island agroforestry systems. On average, each species had 9.2 purposes or uses, ranging from two reported uses per species to as many as 121 for the coconut. These uses did not include the strictly ecological functions such as shading, protection from wind and sand and salt spray, erosion and flood mitigation, coastal reclamation, provision of animal and plant habitats, or soil improvement (Thaman 1989c).