|Agroforestry in the Pacific Islands: Systems for Sustainability (UNU, 1993, 297 pages)|
|3 Agroforestry in Melanesia: Case-studies from Papua New Guinea and the Solomon Islands|
On most of the larger islands of Melanesia, sufficient land and relatively low population densities allow for the practice of extensive agricultural systems within largely forested landscapes. Human settlement and use of these lands have caused a humanization, taming, or "agriculturalization" of the forest. Although there is variation from place to place, the basic agricultural strategy consists of felling or ringbarking some trees and clearing the underbrush while at the same time protecting selected tree species that will remain or be allowed to regenerate as part of the garden of deliberately planted short-term crops and domesticated trees.
In most cases, the debris from forest clearing is allowed to dry and is then burned before or during planting, although in some areas such as on the Great Papuan Plateau in Papua New Guinea (Schieffelin 1975), on the Weather Coast of Guadalcanal, and in the upper Wainimala River area of Tailevu Province, Fiji - burning is discouraged. The debris is allowed to decay around emergent crops, thus retarding soil erosion and enhancing the development of the soil structure and the accumulation of organic matter.
The trees that have been preserved usually have some utilitarian value, such as provision of fruits, nuts, edible leaves, medicines, or wood for special purposes; or trees may be left intact or not weeded out because they improve the soil (e.g., the leguminous Albizia falcataria) or serve as habitats for desired prey such as birds of paradise, pigeons, or flying foxes (fruit bats). When such favoured trees are left unfelled on new garden sites, they are often pruned or pollarded to open up the ground to sunlight, to add additional organic material to the soil, or to provide support for climbing or sprawling crops. Thus, the practice of the classic system of shifting cultivation of gardens in forest results not only in the maintenance of soil fertility on garden sites but also in the development of a humanized forest fallow that itself contains many trees of economic and cultural significance.
The case-studies of Melanesian agroforestry systems presented in this chapter and chapter 4 are drawn from research carried out in various parts of Papua New Guinea, the Solomon Islands, Vanuatu, and Fiji (see map p. 36); the studies illustrate the range of variation possible within this general pattern. Some of the examples described are from areas of relatively low population density (Nduimba Basin in the highland fringe of Papua New Guinea and, in chapter 4, Namosi and Matainasau in Fiji); others are from areas of fairly high density (Buma on Malaita in the Solomon Islands and, in chapter 4, Tanna in Vanuatu). Not included in the Melanesian case-studies, except by inference in the discussion of the highland fringe of Papua New Guinea, is a description of the intensive, quasi-permanent sweet-potato cultivation of the densely settled Papua New Guinea Highlands, where labour-demanding tillage in grasslands is an important aspect of cultivation. But even here, where the forest has largely been replaced by anthropogenic grasslands, trees remain significant. Groves of Casuarina provide wood for fuel and fencing and serve as a planted, soilenriching fallow; Ficus dammaropsis (the "highland breadfruit") provides edible leaves; planted Pandanus conoideus is important nutritionally at midelevations and also in forested areas; and Pandanus julianettii and P. brosimos, which grow spontaneously or as quasi-domesticates in the remaining high-elevation forests above the zone of cultivation, provide oil-rich nuts that are an important supplementary food.
Clarke's (1965) comparative study of the intensification of shifting agriculture in highland Papua New Guinea provides information on variations between the agroforestry systems practiced by people of the highland fringe of Papua New Guinea.
When studied in the mid-1960s (Clarke 1971), the Maring people of the Nduimba Basin numbered about 150 and occupied several square kilometres of mountainous land adjacent to an immense stretch of unoccupied rain forest on the northern slopes of the Bismarck Range. The population density was low- approximately 12 persons per sq km. Within their occupied territory, with elevations centred around 1,000 metres, no more than two per cent of the forest cover had been converted to grassland. In these few areas, the dominant species were Imperata cylindrica and Ischaemum digitatum, both of which are common components in the early stages of the Nduimba Basin plant succession that leads from cleared garden to well-developed secondary forest. Furthermore, the presence in the grasslands of pioneering trees such as Dodonaea and Alphitonia and tree ferns also points to the transient dominance of the grasses.
The comments of the people of the Nduimba Basin support the botanical evidence with respect to lack of pressure on the land. When asked why they had given garden land or usufructuary rights to outsiders, a frequent reply was: "We are a small group, and we have abundant land; therefore we give land away to friends and kin" (Clarke 1965, 348).
Even when compared with other types of simple shifting cultivation, the system in the Nduimba Basin is remarkably casual. Gardens are started sporadically throughout the year; part of the cut debris is usually burned, but the burning phase may be omitted if the weather remains wet. Most men clear their plots in secondary forest; a few of the "very strong men" sometimes make a clearing in the primary forest, a process that is more work than cutting the slenderer trees of the secondary forest. Low bush and the limited grasslands are never used for gardens. No tillage - in the sense of turning or working the soil - is practiced. Neither irrigation nor ditching is present or necessary. The planting tool is a simple wooden dibble. The polycultural mix of many species of tuber and fruit- or leaf-bearing crops that are planted in the gardens provides a fairly good diet, which is complemented by wild plant foods (including wild yams, ferns, nuts, fruits, and leaves) and fish, eels, domestic pigs and fowls, insect larvae, birds, and other wild game from the surrounding forest, fallow areas, and streams.
Maring agroforestry practices come into play particularly when the gardens are left to fallow after the harvest of short-term crops. No fallow cover is planted but, because gardeners deliberately leave tree seedlings in the ground while weeding, the plot is usually well colonized by saplings when cultivation ceases. Additionally, as the harvesting of short-term crops comes to an end, the garden sites are transformed into orchards with major plantings of Gnetum gnemon (fibre, edible leaves and fruit) or Pandanus conoideus (oil-rich mesocarp providing very important supplementary food and condiment) and minor plantings of Artocarpus altilis (breadfruit) and Ficus wassa (bark cloth, edible leaves and fruit). The orchards thus come to be scattered widely throughout Maring territory and provide a valuable supply of materials and foods throughout the year. As they age over several decades, the orchards merge back into secondary forest. Their sites again become available for swidden clearing so that the orchards extend production from garden lands for several decades, while at the same time the land is receiving benefits similar to those gained from fallow under spontaneous secondary forest.
The Maring also recognize unplanted secondary-forest communities as a resource - one that is more valuable than primary forest. Because the secondary forest provides the reinvigorating functions of fallow vegetation that make shifting cultivation possible, it is referred to in the vernacular as the "garden mother." Beyond this important function, the whole secondary zone - which derives from clearing for gardens combined with the protection of tree seedlings during weeding - serves as a foraging zone for domestic pigs and as a hunting ground for the men who pass through it daily on their rounds. The secondary communities also serve as sources of plant foods and materials. The common Alphitonia-Cyathea woodlands provide easily-cut wood for fencing and fuel. In addition, the Cyathea provides edible leaves; and the understorey plants, growing in the light shade, provide cordage, edible leaves, and medicines. The secondary Albizia falcataria community is recognized as most valuable for increasing soil fertility for future gardens, presumably through the usual nitrogen-fixing processes of leguminous plants; Albizia's wood is also valued for carving. Jungle regrowth provides edible leaves as well as wild Musa leaves for wrapping materials and for clean surfaces for food preparation. In other words, not only does the temporal alternation of forest fallow with gardens make the gardens produc five, the successional stages of the forest are themselves valuable for other purposes (Clarke 1971, 60-64).
The people of the Nduimba Basin are not oppressed by garden work. Even the women, who do most of the steady work of weeding and harvesting, frequently take a day's vacation and eat food gathered on the previous day or collect snacks of sugar cane from their nearest garden. Food shortages and crop failures are unknown, and when the gardens are abandoned they contain considerable amounts of unharvested produce.
Kompiai is the name given now to a territory on the southern slopes of the Bismarck Range (Jimi River valley) occupied by the Kauwatyi clan cluster, a group that numbers about 850. The average population density at Kompiai is 29 people per sq km, more than double that in the Nduimba Basin. At Kompiai, retrogressive succession of the vegetation is more advanced than in the Nduimba Basin, which is about 16 km distant. Perhaps as much as 20 per cent of the Kauwatyi land is grassland containing genera such as Themeda, Arundinella, Ophiurus, and Eulalia, which are thought to be indicative of degraded sites. Kompiai has a smaller percentage of primary forest than the Nduimba Basin. On average, the secondary forest at Kompiai is younger, and much of it is floristically less complex; large areas are covered by almost pure stands of the weed tree Dodonaea viscosa - a type of simple regrowth that is absent from the Nduimba Basin.
This circumstantial evidence of an intensity of land use greater than that of the Nduimba Basin is compatible with what the Kauwatyi say about their land and with their quite unusual action in the mid-1950s when they attempted to make gardens in the territory of a defeated neighbour before certain prescribed ritual procedures had taken place. Such an attempt almost certainly indicated considerable pressure on the land because, in this part of Papua New Guinea, the extension of territory is scarcely ever an immediate result of warfare.
The gardens at Kompiai look almost like those in the Nduimba Basin: there is neither tillage, irrigation, nor any attempt to improve soil drainage; nor are the grasslands used for gardens except on rare occasions. The methods of planting, the agricultural tools, and the "messy" intermixture of garden plants are the same in both places. The crops grown are the same, too, but the proportions are different. At Kompiai, sweet potatoes become relatively more important among the starchy staples grown - an indication of the beginning steps toward the very heavy dependence on that crop that characterizes the areas of highest population density in the central highlands of Papua New Guinea, where fields are used almost continuously and forest fallow is wholly absent. The orchards of Pandanus conoideus, Gnetum, and breadfruit are rarer at Kompiai than in the Nduimba Basin, and game is scarcer.
The intensity of harvest and the age and type of fallow cover also vary between the two places. Native informants all agreed that the Kauwatyi harvest their gardens more thoroughly than the inhabitants of the Nduimba Basin. Moreover, when the Kauwatyi decide that an old garden is ready for fallow, they bring their pigs to the plot to root for the small tubers that still remain in the ground. In the same situation, the people of the Nduimba Basin simply abandoned the plot; if the pigs find it, well and good; if not, it does not matter. Doubtless, if the pig herd of the Nduimba Basin were to increase, the Kauwatyi custom would be adopted.
Although fallow periods are shorter at Kompiai than in the Nduimba Basin and consequently there is less well-developed secondary forest, the Kauwatyi habit of planting or encouraging quick-growing Casuarina oligodon trees in old gardens may slow the decline in soil fertility associated with decreasing lengths of fallow between periods of gardening. Interestingly, although the people say that the soil under Casuarina groves is better than that under other types of fallow, the main motive for planting the trees seems to be to obtain wood for fences, fuel, and house construction. Despite the value placed on the trees, the people's efforts to establish groves of Casuarina are haphazard; if the bare ground of a new garden develops Casuarina seedlings, the gardener cherishes them; but if seedlings do not develop, he does not always transplant seedlings into the garden (Clarke 1965, 349-352).
In contrast, not far away in the upper Kaironk Valley - where population density is even higher, and spontaneous forest almost absent except on the cloudy mountain crests - planting of Casuarina as a fallow cover for gardens is much more systematic. Groves of these graceful trees dot the grassy landscape, and a high percentage of the gardens are planted beneath pollarded Casuarina. Despite the soil improvement brought by these nitrogen-fixing trees, land degradation has proceeded in the Kaironk to the point where labour-intensive tillage is required to maintain soil fertility, and sweet potatoes (which require a less fertile soil than Colocasia taro or yams) are far more important than at Kompiai or in the Nduimba Basin.
Implications of increasing agricultural intensification
The variations between the agro-ecosystems of the Nduimba Basin, Kompiai, and the Kaironk Valley can be interpreted as a sequence of increasing agricultural intensification. The consequences of a decline in the amount of well-developed natural forest because of extended cropping cycles and shortened fallow periods (caused in part by a recent expansion of smallholder commercial coffee planting and beef cattle production) include an increase in the intensity of garden harvesting, an increasing use of agronomic techniques to maintain soil fertility, a decline in yield per unit labour, and a concentration of effort towards production of the highest-yielding crops (sweet potatoes in the highland New Guinean case). The implications for agroforestry are that, as primary forest and well-developed secondary forest are converted to grassland or impoverished scrub under regimes of increasing population density and shortened fallow, the resources available from forest disappear, and the regenerating "work" done by the forest must be taken over by the human cultivators if an acceptable level of soil fertility is to be maintained. In parts of New Guinea a traditional solution to the loss of spontaneous forests was the creation of artificial forests of Casuarina (or Dodonaea viscosa in some places) to aid soil regeneration and to provide wood for fuel and fencing. Although of great value, such single-species stands of trees did not provide the variety of wildlife habitats or the food, medicine, or other materials found in the more species rich natural forests.
In 1972, population densities on the Weather Coast of southern Guadalcanal, the Solomon Islands, ranged from 1.5 to 26.4 persons per sq km (Chapman and Pirie 1974). Pressure on land was low in the vicinity of Kologhona village, some 10 km inland from Babanakira in the upper Tina River Basin of the Wanderer Bay area. The village, which had a population of approximately 60 in early 1975, had access to extensive areas of alluvial and colluvial soils, steeply sloping garden land covered with secondary forest, and considerable areas of slightly disturbed primary forest along the crests of the ridges and on the steeper slopes.
The two most common subtypes of agroforestry practiced in Kologhona are ago-puka and ago-male. The ago-paka method is practiced in old forest at some distance from the village. All but the biggest trees are felled, after which the debris is piled around the bases of bigger trees and burned. No attempt is made to clear all stumps or level the ground before planting commences. Traditionally, planting was almost exclusively women's work, using digging sticks and hoes; men are increasingly doing more of this work. Yams and Colocasia taro are the most common crops planted in these gardens, although other ground and tree crops are also planted. Fallen trees are allowed to lie in the garden, often placed along contours to retard erosion and to provide for trellising yams and other climbing plants.
In the more heavily cropped alluvial and colluvial soils and gardens closer to the village, the ago-male method is more common. Its practice means the extension of existing gardens into surrounding secondary vegetation by clearing, moving the debris to the side, and planting without burning (Rainbow and Teteha 1983). Sweet potato is the major crop in these gardens, intercropped with yams, taro (Colocasia and Xanthosoma), banana cultivars, and a diversity of other crops, including sugar cane, Saccharum edule, Hibiscus manihot, pumpkin, pineapple, maize, chill) peppers, and tobacco.
Trees with edible fruits and nuts are commonly protected when secondary vegetation is cleared, or they are planted amongst crops. Trees so treated include breadfruit, coconut, betel-nut, papaya, Citrus spp., Canarium spp., Inocarpus fagifer, Barringtonia edulis, Syzygium malaccense, and Ficus copiosa. Other useful tree or tree-like species maintained in gardens include Pandanus tectorius, kapok (Ceiba pentandra), and sago palm (Metroxylon salomonense) and
Heliconia indica, both of which are found mostly in poorly drained areas close to the river. In fallow areas, the commonest pioneer species are Kleinhovia hospita, A lstonia spp., Ficus spp., and Macaranga aleuritoides. Wild foods - including wild yams (Dioscorea spp.), a range of ferns, and other wild greens - and animal foods are either preserved through selective weeding or occur in fallow and secondary vegetation.
Despite increasing population pressure, the preservation of trees as part of an integral agroforestry system has continued. However, increasing pressure by the government to expand monocultures of copra or cocoa and the smallholder production of beef cattle, with no emphasis on the maintenance of arboreal diversity, is accelerating agrodeforestation on the Weather Coast and will play a major role in the decline of arboreal diversity and self-sufficiency and the loss of knowledge of traditional agroforestry systems among young agroentrepreneurs.
With a population density of 14.2 people per sq km in 1976, the island Malaita was (and remains) one of the more densely populated provinces of the Solomon Islands (Solomon Islands Government 1979). While more than 68 per cent of all rural Solomon Islands adults were fully engaged in subsistence or semi-subsistence agriculture and another 23 per cent were partly so engaged, comparable figures for Malaita were 77 per cent and 17 per cent respectively (Eele 1978). On Malaita, only 1,467 people were employed wageearners; most Malaitans gained their livelihood through subsistence fishing, shore and reef gathering, and shifting agroforestry. The pressures, however, for increased cash income through smallholder cattle ranching and cocoa and copra production were having a significant impact on the sustainability of shifting agroforestry on Malaita. This was readily apparent at Buma, a coastal village of approximately 361 Kwara'ae-speakers, located approximately 9 km north of Auki, the provincial capital.
The systems of shifting agroforestry at Buma, and throughout much of Malaita, are not unlike the ago-paka and ago-male systems of Kologhona, except that burning is a characteristic feature of all Buma systems. Almost all shifting agroforestry is practiced on well-drained lowland rain forest or secondary forest fallows, on both steep and level terrain. Selection of garden sites is determined by distance from the village and older gardens, availability of adjacent or nearby fallows for future plantings, soil and fallow characteristics, and previous productivity of the site (Manner 1980). New gardens are usually located adjacent to producing gardens, which serve as sources of planting materials for the new gardens. The old gardens are thus extended in a style resembling the linear arrangement of gardens described by Oliver (1955) and Connell (1978) on Bougainville.
Both men and women participate in gardening activities such as slashing the undergrowth, transporting planting materials, burning, planting, and weeding. Men are usually responsible for the more arduous tasks such as tree felling, log removal, and their emplacement as boundaries. All trees except Areca catechu, Artocarpus altilis, and Canarium indicum are cut down by axe. After a drying period of 1-2 weeks, the litter is gathered into small piles and burned. If young (5-12 years) secondary forest is cut for gardening, the Buma Kwara'ae ensure that all parts of the garden receive ash. On the other hand, if mature secondary forest or rain forest is felled, the regrowth is slashed and the litter burned - although little is done to ensure that all parts of the garden receive ash.
The cleared plot is marked off into sections, then a dibble stick is used to plant a wide variety of root-crop cultivars, fruit and nut trees, and other crops such as pineapple, water melon, Hibiscus manihot, tomatoes, and tobacco (table 4). Newly cleared gardens (2-4 months old) are dominated by taro (Colocasia esculenta), giant taro (Alocasia macrorrhiza), and the sweet or lesser yam (Dioscorea esculenta). As taro and other cultigens mature, replanting is carried out. By way of contrast, older gardens are dominated by Alocasia macrorrhiza, pineapple (Ananas comosus), sweet potato (Ipomoea batatas), and a heavier weed cover. The gardens are abandoned to fallow two years after initial planting.
This human-directed succession of cultivars and the release of gardens to fallow can be seen as a reflection of Kwara'ae understanding of crop requirements and ecological processes. The presence of sweet potatoes and cassava in older gardens indicates poorer soil fertility a condition to which these species are adapted (Haynes 1977; Thaman 1976; Thaman and Thomas 1982, 1985). Bananas and other tree and shrub crops, because of their height and longer growth cycles, may be better adapted to resist the increased weed and pest in festations of older gardens. Their more extensive rooting systems may also be more efficient in nutrient uptake than shorter-lived plants. Finally, as the fallow period continues, there is the increasing regeneration of pioneering forest trees, which brings renewed fertility and filth and increases habitats for other forest-dwelling organisms. Wild food products multiply and noxious garden pests disappear. In addition, the mixed forest is the source of building materials, medicines, dyes, and food; and its regeneration may help to maintain the cultural and economic stability of the Buma Kwara'ae. Major tree or tree-like species include a range of bananas and plantains (Musa cultivars), the culturally important betel-nut (Areca catechu), the ngali nut (Canarium indicum), papaya (Carica papaya), and the nutritious hibiscus spinach (Hibiscus manihot) (table 4).
Monetization and agrodeforestation
For the past two decades, the sustainability of the Kwara'ae shifting agroforestry system has been threatened by government-sponsored smallholder cattle, cocoa, and copra projects, and by sweet potato cashcropping for the Auki market. The resultant agrodeforestation brought about by the increasing emphasis on cash cropping has greatly increased pressures on Buma land resources and caused the spatial displacement of traditional agroforestry, a process noted as occurring elsewhere by Chapman and Pirie (1974) and Quartermain (1980). At Buma, cocoa is intercropped with coconuts, and cattle are grazed under coconuts and other valuable tree species. Prior to these introductions, the Buma Kwara'ae practiced traditional agroforestry on lands classified as "highly suitable agricultural opportunity" areas (Wall and Hansell 1974), and which were located within 15-30 minutes walking time from the village. Today, however, most traditional agroforestry is practiced on more distant and steeper-sloping lands. Walking times to these areas range from 30 to 60 minutes. Unfortunately, the burden of transporting garden produce, which may weigh as much as 15 kg per trip, often falls on the women. The Buma Kwara'ae have potential gardening sites located 2 hours farther inland, but few gardens have been cleared in these relatively distant areas. It is ironic that a major reason for this decline in traditional agroforestry is narrowly focused, institutional smallholder agroforestry focused primarily on the tree crops, cocoa and coconuts.
Similarly, cash cropping of sweet potatoes for the Auki market has also displaced traditional agroforestry farther inland. Moreover, this cash cropping is conducted in forest or bush fallows often less than 3 years old. This shortening of the gardening cycle has led to significant soil deterioration and a retrogression of the fallow vegetation from the useful arboreal species that characterized traditional forest fallow to a community dominated by Acalypha grandis, ferns, and Imperata cylindrica.
Table 4 Species composition of Buma village gardens, West Kwara'ae, Malaita, the Solomon Islands. (Data expressed as number of plantings per 5m x 5m quadrat; C =cormels; D = dominant crop)
|Garden age||2-4 months||6-12 months||12-18 months||18+ months|
|Scientific name (Kwara'ae or common name)|
|Alocasia macrorrhiza(giant taro)||2||5||5||5||19||19||2||4||3||12||3|
|Ananas comosus (pineapple)||4||6||9||5||7||3||2|
|Areca catcheu (betel-nut)||1|
|Canariurn indicum (ngali nut)||1|
|Carica papaya (pawpaw)||11||1|
|Colocasia esculenta (taro)||38||42||2||2||15||13C||2C||2C||7C||15C|
|Citrullus lanatus (water melon)||2||1|
|Dioscorea esculenta (sweet yam)||16||17|
|Hibiscus manihot (hibiscus spinach)||5||1||1||2|
|Ipomaea batatas (sweet potato)||10||5||D||D||D||D||9D||D||D||D||D|
|Lycopersicon esculentum (tomato)||1||1|
|Manihot esculenta (cassava)||4||2||9|
|Musa cultivars (banana/plantain)||2||1|
|Nicotiana tabacum (tobacco)||1||2||1||2|
|Number of species||5||3||4||5||2||5||5||3||4||5||3||6||2||2||5||3|
Source: Adapted from Manner 1980.
Among the most thorough accounts of traditional Pacific agroforestry are those of the south-eastern Solomon Islands by Yen (1974, 1976a, 1976b) and of the Polynesian outlier Tikopia by Kirch and Yen (1982). These works, coupled with Powell's (1976b) study of plant communities and Hendren's (1976) study of Ulawan settlement patterns, provide an excellent basis for understanding agroforestry in the south-eastern Solomon Islands.
The areas studied include the island of San Cristobal (3,500 sq km); the smaller islands of Ulawa and Santa Ana; the Santa Cruz group, including the main island of Nendo (660 sq km); and the islands of Utupua and Vanikolo, the Duff Islands, the main and outer Reef Islands, and the Polynesian outliers of Anuta and Tikopia in the far south-east. The environments of these islands range from the heavily forested interiors of the larger high islands of San Cristobal, Nendo, Utupua, and Vanikoro (which is over 900 metres in elevation) with extensive coastal plains and swampy areas, to smaller volcanic islands, and the coral atolls of Nupani and Nukapu in the outer Reef Islands with very restricted floras.
The dominant agricultural system in most of the south-eastern Solomon Islands is shifting cultivation, with yams (Dioscorea alata and D. esculenta) and taro (Colocasia esculenta) the dominant staples in newly cleared plots. Sweet potatoes (Ipomoea batatas) are commonly planted next in succession. Primary forest is rarely cleared; rather, secondary forests on coastal plains and lower slopes are the most common sites for new gardens. Some inland forest sites are occasionally cleared for yam gardening, including the cultivation of minor species such as Dioscorea pentaphylla, D. nummularia, and D. bulbifera. Yams often occupy drier sites, whereas taro, which is often planted twice before letting the land revert to fallow, occupies wetter areas. Giant taro (Alocasia macrorrhiza) is occasionally planted as a supplementary staple (Hendren 1976; Kirch and Yen 1982; Powell 1976b; Yen 1973, 1976a, 1976b).
Gardens are usually cropped for no longer than three years, with fallows ranging from 6 to 12 years. More permanent gardens of perennials such as Cyrtosperma chamissonis and trees are also found in some areas, such as Nendo. Wetland cultivation of taro and sago palm (Metroxylon salomonense) is practiced in the Duff group. On Anuta and Tikopia, more permanent or intensive systems incorporating cassava into taro-cassava or sweet potato-cassava rotations have displaced yam cultivation.
The greater intensity of land and resource utilization on the small isolated islands of Anuta and Tikopia is evidenced by the great diversity of seasonal surpluses of foods stored using pit-preservation or ensiling by semi-anaerobic fermentation. Herbaceous and tree species thus utilized included breadfruit, Burkella fruit, Ananas and plantains, sago, taro, cassava, Polynesian arrowroot (Tacca leontopetaloides), giant taro (Alocasia macrorrhiza), and giant swamp taro (Cyrtosperma chamissonis) (Yen 1976a). Further evidence of intensification is provided by the existence of walled garden complexes (hatarau or pwainua) and non-irrigated terraces on Ulawa (Hendren 1976) and stone-walled terraces on Anuta (Yen 1976a).
Agroforestry and arboreal components
All agricultural and land-use zones have major arboreal components. The main species found in villages and home gardens, in permanent village tree groves, and as protected or deliberately planted intercrops in coastal and inland food gardens include coconut palms (the most common intercrop), a wide range of banana and plantain cultivars (Musa cultivars), breadfruit (Artocarpus altilis), sago palm (Metroxylon salomonense), the nut trees Canarium spp., Barringtonia edulis, Inocarpus fagifer, and Terminalia catappa, Burkella obovata, edible pandanus (Pandanus dubius), Malay or mountain apple (Syzygium malaccense), oceanic Iychee (Pometia pinnata), the hogplum or Polynesian vi-apple (Spondias dulcis), Gnetum gnemon, edible figs (Ficus spp.), and the betel-nut palm (Areca catechu). More recent introductions include mango (Mangifera indica), citrus trees (Citrus spp.), and papaya (Carica papaya). Of the non-food species, Ceiba pentandra is very common.
Other less common or locally important species found planted or protected in gardens and tree groves include Antiaris toxicaria, Sterculia sp., Semecarpus sp., and Corynocarpus cribbeanus, with Sterculia and Semecarpus being planted in breadfruit groves as living ladders. Species found around former inland settlement sites include Areca catechu, Burkella obovata, Terminalia catappa, Gnetum gnemon, Corynocarpus cribbeanus, and Cordyline fruticosa and Cyathea sp.
Shrubby or herbaceous supplementary food species intercroppped in food gardens and planted in villages and home gardens include hibiscus spinach (Hibiscus manihot), sugar cane (Saccharum officinarum), Cordyline fruticosa (also represented by cultivars of ornamental and magical or ceremonial importance), edible panax (Polyscias fruticosa and P. scutellaria), and maize (Zea mays) and non-food species such as Pandanus spp., Euadia sp., Alpinia sp., Codiaeum variegatum, Gardenia sp., Halfordia sp., and tree ferns (Cyathea sp.). Species commonly planted along garden borders or as hedges include vegetatively planted Barringtonia edulis cultivars, Ananas and plantains, sugar cane, Cordyline fruticosa, and Polyscias spp.
For many of these species, both wild (or feral) and cultivated forms are recognized, with numerous cultivars or varieties specified for the more common species. For example, there are 13 varietal forms of coconut, 33 banana or plantain cultivars, 18 breadfruit cultivars, 3-5 cultivars each for Canarium spp., Pometia pinnata, Barringtonia edulis, and Burkella sp., and at least 2 cultivars each for Terminalia catappa, Metroxylon salomonense, and Gnetum gnemon. The wide range of arboreal husbandry strategies includes deliberate planting of seeds, shoots, branches, and other vegetative parts, the transplanting of self-sown seedlings, and their protection in fallows. Of particular interest is the hypothesis that many trees that grow wild elsewhere (e.g. Burkella obovata, Pometia pinnata, and Calophyllum inophyllum) have been domesticated or semi-domesticated in the southeastern Solomon Islands because of the "accent on trees there" resulting from "an intensification of attention on the gathering aspect of subsistence economy." This focus on arboriculture seems to be Melanesian (that is, nonAustronesian) rather than Austronesian or Polynesian (Yen 1974).
None the less, arboriculture in the definitely Austronesian areas, such as on the Polynesian outlier of Tikopia, also reflects great agroforestry sophistication, possibly as a result of continued contact with Melanesia. Because of the unusual richness and significance of the Tikopian orchard tracts, the description of them by Kirch and Yen (1982, 38-39) is provided at some lenght:
The orchard tracts are not exclusively devoted to productive trees. Rather, they mimic the mixed nature of the low-altitude forest associations typical of the Solomon Islands flora, not only in tree species, but also in the subcanopy. These artificial associations are exemplary of the multi-storey forms of cropping sometimes recommended as innovations for modern agricultural development in the Pacific, but which actually already exist as indigenous adaptations (Ward and Proctor 1980), albeit sometimes erased by the adoption of commercial cropping modes. A characteristic Tikopia orchardholding has a lower planted storey of Cyrtosperma, which, it should be noted, is adapted well beyond its "swamp taro" environment. Bananas generally form the second storey upward, but in scattered distribution, their situation being favored by more open portions of the canopy. The vines of Piper belle may climb to quite prodigious heights on trees, but are generally kept in control by constant picking for betel chewing, while the yams . . . climb to the upper reaches, depending on season and time of planting. The density and diversity of the middle storey is compounded by the presence of Antiaris and Gnetum trees, the occasional cycad, and the saga palm at different stages of growth before flowering or maturity, when its height may reach 20 meters. The bulk of the canopy, generally below that height, consists of the orchard trees proper- breadfruit, Eugenia, lnocarpus, Spondias, and the occasional Calophyllum. On the flatland and at lower altitudes (below 50 meters above sea level), this list is often enriched by Canarium, Burkella, Terminalia catappa, Barringtonia, and Pometia.... The coconut, important not only as a food source but also for its multiple industrial uses, does not form the familiar belts of Pacific island strands; rather it is distributed on Tikopia throughout the orchard gardens, in all but the highest sections of the island to protrude above the canopy of economic trees.
More monocultural smallholder coconut plantations, the main source of cash income, extend from coastal plains up to an elevation of 22 metres. Breadfruit and bananas or plantains are planted in almost monospecific groves or patches on the coastal plains and near active garden areas.
When clearing secondary vegetation for new gardens, most of these species are preserved, although some - such as Pometia pinnate and Ficus spp. - may be severely pruned or pollarded to open up new garden areas to sunlight and to provide additional organic material or ash. Self-sown seedlings of these species are also protected through selective weeding and are allowed to regenerate as part of the fallow vegetation.
Pioneer species, which are abundant in secondary and open disturbed forest and common in young regrowth in still-productive gardens on most of the larger islands, include Macaranga, Trema, Pipturus, Ficus, Glochidion, Acalypha, Piper and Euodia spp., Morinda citrifolia, Kleinhovia hospita, and Hibiscus tiliaceus. Species more prominent in mature secondary or older regrowth forests, ready for reworking into gardens, include many of the commonly cultivated species such as Pometia pinnata (often as a dominant), Canarium spp., Artocarpus altilis, Syzygium spp., Burkella obovata, Antiaris toxicaria, Spondias dulcis, wild varieties of Areca catechu, stands of bamboo (possibly including both Schizostachyam glaucifolium and Bambusa spp.) along with the indigenous species, Alphitonia incana, Securinega flexuosa, Pterocarpus indicus, Semecarpus sp., and Dysoxylum, Ficus and Elaeocarpus spp. Less common secondary forest species include Stemonurus sp., Boerlagiodendron sp., Horsfieldia spicata, Nauclea orientalis, Garcinia sessilis, Cryptocarya medicinalis, Pimleodendron amboinicum, with common understorey species in mature fallow forest including Cordyline fruticosa, Fagraea racemosa, Euadia, Psychotria, Calophyllum, Codiaeum, Dracaena, and Pseuderanthemum spp. (Powell 1976b).
The climax or only partially disturbed inland forests of the larger islands provide the main hunting and gardening reserves; the dominant trees are Agathis macrophylla, Terminalia calamansanai, Calophyllum vitiense, Dacrydium elatum, and Albizia falcataria with Campnosperma brevipetiolata being common in more disturbed areas.
Protected areas of coastal strand, mangrove, or coastal plain and lake-shore vegetation can also be seen as integral to traditional agroforestry strategies in the south-eastern Solomon Islands. Species commonly found in these areas include Calophyllum inophyllum, Pandanus tectorius, Casuarina equisetifolia, Hibiscus tiliaceus, Terminalia catappa, Inocarpus fagifer, Cerbera manghas, Barringtonia asiatica, Barringtonia racemosa, Heritiera littoralis, and Intsia bijuga. Less common species include Thespesia populnea, Cordia subcordata, Hernandia nymphaeifolia, Tournefortia argentea, and Pisonia grandis.
The "extension of strand vegetation" inland was encouraged through the tending of coastal tree species of value for consumption and industrial use. There were also plantings of feral genera such as Pandanus, Barringtonia, and Terminalia, and species such as Calophyllum inophyllum (Yen 1976a). C. inophyllum, in particular, was commonly planted in the main Reef Islands and domesticated and seed-sown in large-scale plantings (aururakau o ngatai) for the purpose of shore-line stabilization and in garden areas up to 300 metres on Tikopia, with Casuarina equisetifolia, H. tiliaccus, Ochrosia sp. (Neisosperma oppositifolia?), and Pipturus sp. reportedly being semi-domesticated and planted inland and for coastal stabilization.