| Agroforestry in the Pacific Islands: Systems for Sustainability (1993) |
|6 Agroforestry in Micronesia|
Traditional agroforestry in the high islands of Micronesia
Traditional subsistence agriculturalists of the higher and larger islands of Micronesia developed a wide range of agricultural technologies and systems for the production of food under different environmental conditions and in different locations. These included permanent systems of wetland taro cultivation, mixed tree gardening, intermittent tree gardening (shifting cultivation), home or kitchen gardening, and open grassland cultivation (Falaoruw 1985; OTA 1987). The use of any one of these systems did not preclude the use of others. Most islanders produced food using all five systems and, in addition, exploited the reefs and ocean for marine products. Most attention will be given here to mixed tree gardening, an elaborate and refined indigenous agroforestry that is the predominant rural land use on many Micronesian high islands (table 7; Raynor and Fownes 1991a, 139). The other four systems will be briefly discussed, particularly with regard to their relationship to trees.
Table 7 Areas in hectares of land classes in Micronesian high islands. (Total agroforest includes agroforest/tree gardens and coconut plantations; Truk data are for the high islands of Moen, Dublon, Fefan, and Eten only)
|Secondary forest and vegetation||594||1,272||1,843||252||553|
Sources: Belau: Cole et al. 1987; Kosrae: Whitesell et al. 1986; Pohnpei: McLean et al. 1986; Truk: Falanruw et al. 1987a; Yap: Falaaruw et al. 1987b.
Wetland taro cultivation
The production of Colocasia esculenta and Cyrtosperma chamissonis taros in essentially permanent patches has long been practiced on all the high islands of Micronesia, often by means of sophisticated systems of water management that minimized soil erosion and stagnation of water. Favoured areas for the wetland cultivation of taro are alluvial bottom lands and the lowland swamps and marshes located inland of the mangroves, generally within agroforests (Falanruw 1990). The taro patch may act as a filter to minimize sedimentation of the lagoons and ocean (Falanruw 1990; OTA 1987). When a patch under fallow is selected for replanting with Colocasia esculenta, it is cleared of vegetation and drained, the soil is dug up, and various leaves, twigs, and sea grasses are added as a mulch or green manure (OTA 1987), with Wedelia biflora, Carica papaya, and Macaranga sp. recognized as good manuring species (Sugiura 1942). After mulching, the patch is worked to produce a fertile muck of desired consistency and planted with cormels or corm tops. Harvesting occurs six months to a year after planting, and the patch may be replanted to provide a continuous supply (OTA 1987). If the yield or quality declines, the patch is allowed to lie fallow for a number of years.
The cultivation of Cyrtosperma chamissonis requires less labour and attention than is needed for Colocasia (Falanruw 1990; McCutcheon 1981). Green manures are not added to the soil to improve its fertility for cultivation of Cyrtosperma chamissionis, and cultivation methods include the periodic removal of fallen vegetation and debris in order to maintain the flow of water through the system. Cyrtosperma is more shade-tolerant than Colocasia and thus more compatible with tree culture, and an integral part of the agroforestry system of Yap (Falanruw 1990, 97-98). Cyrtosperma is the preferred aroid in Yap (Hunter-Anderson 1984) and Truk (Alex 1965); Colocasia remains the preferred food in Pohnpei (Hunter-Anderson 1984), where not all of the trees were cut back during garden clearance, with some, such as Hibiscus tiliaceus, being left standing to provide shade for the young plants.
Mixed tree gardening
A very well developed form of traditional agroforestry in Micronesia is the tree garden or agroforest (Falanruw et al. 1987a; 1987b; OTA 1987). Except for the initial planting and care while the trees are young, this agroforestry system requires little energy input, but provides Micronesians with an abundant supply of different tree crops and products from marginal lands over a long time period, while maintaining a permanent canopy cover. Except in Palau, such agroforests cover considerable areas of high-island Micronesia (table 7).
The composition and structure of these agroforest gardens varies from place to place. In coastal areas, they tend to be relatively simple, consisting of few species, dominated by coconuts. In Truk, breadfruit is a dominant species of mixed tree gardening (Goodenough 1951). In Guam, breadfruit, coconuts, and Cycas circinalis were harvested from mixed tree gardens. In Palau, these mixed forests were called chereomel and consisted of a wide range of food, fruit, and timber trees, including coconuts, mango, breadfruit, Terminalia catappa, and Inocarpus fagifer (McCutcheon 1981). The forests serve as a habitat for feral and domesticated animals, provide traditional medicines and other culturally valued products, and are or were a source for canoe hulls, building materials, and firewood.
As Falanruw (1990, 98) explains for Yap, the likely development process of tree gardens was the planting of trees for food and other uses around homesteads and in the drained areas created by the excavation of taro patches and the construction of drained paths between homes and villages. These home and path-side tree gardens became confluent and today make up a significant proportion of the island's terrestrial vegetation and contain about 50 native and introduced tree species, such as coconut, breadfruit, betel-nut (Areca catechu), Inocarpus fagifer, many varieties of banana and citrus species, Pangium edule, papaya, cacao, and guava. Of species that have long been cultivated on Yap, there are numerous named varieties-for example, 21 named coconut varieties and 28 named breadfruit varieties. Tree gardens are reported to be largely self-fertilizing. Owners maintain their tree gardens by selective pruning and removal of undesirable trees; occasionally desired trees are planted. Once established, such tree gardens require little maintenance.
The most detailed recent description of indigenous agroforestry in Micronesian high islands is the account by Raynor and Fownes (1991a; 1991b) of Pohopei, where the traditional agroforestry system still supports most of the island's 28,000 people despite increasing emphasis on the cash economy.
The general characteristics of the Pohnpeian agroforestry system are an extensive, permanent overstory of breadfruit, coconut, and forest trees above fruit and multipurpose trees, and an understory of shrubs, root crops, and herbaceous plants. Although sharing many characteristics of homegardens, the system is best classified as a ``multistory,, tree garden because it is not limited to the area immediately surrounding the house compound but extends throughout the landscape. Breadfruit and yams (Dioscorea spp.) are the major staples, and complement each other in seasonality.... Hibiscus tiliaceus is the premier "multipurpose" tree, because it is used for firewood and light construction, poles or whole trees are used for yam trellises, its leaves are used as green manure in soil pits dug for yams, its bark for rope, and its inner bark for best fibers for straining mashed Piper methysticum roots for drinking (Raynor and Fownes 1991a, 140).
Raynor and Fownes (1991a) carried out intensive sampling in 54 landholdings on Pohnpei and enumerated 102 different species, 26 of which were upper canopy species, 39 were sub-canopy, and the remainder were understorey. A few species found on nearly every holding constituted the typical Pohnpeian agroforest: coconut, breadfruit, Cananga odorata, mango, Musa spp., Hibiscus tiliaceus, Morinda citrifolia, Alocasia macrorriza, Dioscorea alata, and Piper methysticum. As on Yap and elsewhere, several of the important species have many recognized cultivars, a diversity that is an important component of the aggregate biological diversity of Micronesian agroforestry systems (Raynor and Fownes 1991a, 151).
Because they could detect no patterns in species composition dependent on elevation, soil type, or particular region, Raynor and Fownes (1991a, 155) concluded that " . . . the Pohnpeian agroforest is a managed landscape, despite its superficial resemblance to forest. Species presence or absence was apparently more strongly controlled by farmers' decisions than ecophysiological constraints."
Intermittent tree gardening (shifting cultivation)
Intermittent tree gardening (i.e., shifting cultivation, or swidden) is practiced in secondary forest fallows on all high islands of Micronesia. Structurally and functionally, this system is little different from shifting cultivation systems described for the other parts of the Pacific, except that in Kosrae burning was not used in garden clearing (Wilson 1968). In contrast to mixed tree gardening, intermittent tree gardening is not a permanently productive form of land use. When the gardens, cleared from forest, are no longer harvested after one to two years of production, the site returns to fallow, succeeding through stages to a forest of spontaneous secondary species, here and there enriched with useful species such as breadfruit planted during the garden phase. The major crop in such gardens is yams of the genus Dios corea - six species of which and 34 locally recognized varieties have been recorded from Yap (Falauruw 1990, 99).
Home gardens and lanchos
Throughout high-island Micronesia, home gardens are a common feature of most households. In Guam and the Northern Marianas a variation of the home garden is known as the lancho. These provide villagers with a ready source of food, fruit, spices, herbs, and, in some cases, medicinal plants. In urban areas, these gardens are, in the main, supplementary to a wage income.
Out of an extensive pool of fruit-trees, the most commonly found are varieties of citrus, coconuts, breadfruit, and bananas. Ornamental trees and shrubs, some of which have ritual or ceremonial significance, are other components of kitchen gardens. Hibiscus hybrids, Cordyline fruticosa, and Codiaeum varigatum are as significant in the Micronesian high islands as they are in Melanesian and Polynesian societies. The latter two species were sometimes not planted in Palauan house gardens because of their association with death and the supernatural (McCutcheon 1981). In Guam, the "pickle" tree, or bilimbi (Averrhoa bilimbi), carambola (Averrhoa carambola), mango, coconuts, soursop (Annona muricata), perennial chill) (Capsicum frutescens), annatto (Bixa orellana), Citrus spp., Jatropha integerrima, Cycas circinalis, Plumeria rubra, P. serratifolia, Araucaria excelsa, and Dracaena marginata are found in many home gardens. In Palau, the betel pepper vine (Piper betle) was zealously guarded against theft (McCutcheon 1981). Other useful plants were Areca catechu, Citrus mitts, and Muntingia calabura (McCutcheon 1981). Sproat (1968) notes that Crateava speciosa has special importance in the central Caroline Islands.
For Guam and the Northern Marianas, there is little documentation of traditional subsistence cultivation. Prior to European contact, the indigenous Chamorros were mainly dependent on the ocean; root crop agriculture was rudimentary and supplemented by hunting for fruit bats, birds, and land crabs (Underwood 1987). However, under Spanish rule, and by the end of the nineteenth century, subsistence agriculture on the ranch (lancho) became accepted as the Chamorro way of life (Underwood 1987). Today, most ranchos are located in southern Guam and consist of a simply built cooking and sleeping house surrounded by food trees, chickens, pigs, and gardens (OTA 1987). Relatively few ranchos are cultivated without the use of ferti lizers or pesticides, and not all of the production is consumed at home. In the Northern Marianas, ranchos are more difficult to find because of the impacts of economic development, division of family lands, foodstamp programmes, and population increases (OTA 1987; Sproat 1968). During the Japanese administration of the Northern Marianas, traditional subsistence agriculture was replaced by the development of sugar-cane plantation agriculture.
Traditional open-canopy (ked) agriculture
The ked area lying in the interior region of Babeldaob, Palau, is characterized by exposed and eroded oxisols and ultisols, and a degraded vegetation (McCutcheon 1981). Ked also refers to the fertile grassland areas in Palau, Yap, and Pohnpei, which are used for traditional subsistence agriculture (Hunter-Anderson 1984).
Ked agriculture involves burning the grass, turning the friable soil, and hoeing ridges along the contour to reduce erosion (McCutcheon 1981). Mulching (with sea grass and Cymbopogon citratus) and ditching are other features of this open-canopy agriculture (OTA 1987). Sweet potatoes, Colocasia taro, Manihot esculenta, and pineapple are the most commonly planted crops. Cymbopogon citratus (lemon grass) is planted as a border and to prevent soil erosion (McCutcheon 1981). With crop rotation to reduce species-specific insect predation, the ked garden can be cultivated for many years without fallowing (McCutcheon 1981).
On Yap, crops grown in open areas include sweet potatoes, cassava, and vegetables. The making of sweet-potato gardens involves the construction or reconditioning of drained garden beds by cutting or burning the vegetation on the site, piling the debris on the garden area, and sometimes adding additional mulch, including washed up sea grass. Ditches are dug or deepened around the garden bed, and the soil piled on top of the mulch, a process that drains the garden bed, suppresses weeds, and provides a fertile soil-mulch-soil sandwich. Open-canopy gardening on Yap today is reported to be causing a retreat of forest and an exhaustion of soils under secondary vegetation because of careless and too-frequent burning and too-short fallow periods between gardening (Falanruw 1990, 101-102).
The ditching, mulching, and other garden preparation activities, and the relatively long period of cultivation of ked agriculture, are very similar to the intensive, semi-permanent forms of cultivation found in Papua New Guinea grassland ecosystems. On the other
Micronesian high islands, agricultural mounds and terraces, with or without stone facing, attest to the intensive and long-term cultivation of food crops. In Pohnpei, for example, bananas, coconuts, Piper methysticum, and Alocasia macrorrhiza are grown in earthen mounds and hillside terraces (Hunter-Anderson 1987).
Sustainability of Micronesian high-island agroforestry
It is clear that in the high islands of Micronesia, subsistence agroforestry has a long history and has successfully incorporated many recently introduced cultigens into the continuing evolution of traditional systems. High-island peoples developed both permanent and impermanent forms of agroforestry that provided food and materials from a large number of cultivated species and varieties. Raynor and Fownes (1991b, 164) specifically address the question of the sustainability of the Pohupeian agroforestry system, noting that Pohnpei is thought to have been settled for at least 2,500 years, and supported a pre-European-contact population as large as 50,000, compared with 30,000 in 1990. Twenty-two of the 54 farms surveyed by Raynor and Fownes were reported to be over 100 years old, but farmers claimed that many of them had been farmed as long as people had been there. The presence of domesticated trees and abandoned garden beds in today's forests on Pohnpei and Yap, and probably on other Micronesian high islands, demonstrates that the conversion of forest to garden and back to forest has a long history (Falanruw 1990, 102; Raynor and Fownes 1991b, 164). The future sustainability of high island agroforestry probably depends less on ecological than on human factors, including not only knowledge of the systems and attention to their careful management but also the desire to maintain them in the face of food imports and the tendency of young people to seek wage employment in town or to emigrate (Raynor and Fownes 1991b, 164). For the present, traditional agroforestry and subsistence agriculture remain important land uses in many high islands of Micronesia but are hardly practiced at all any longer in Guam and the Northern Marianas.