|Agroforestry in the Pacific Islands: Systems for Sustainability (UNU, 1993, 297 pages)|
|5 Agroforestry in Polynesia|
Decker's (1971) study of "Plants, Man and Landscape in Marquesan Valleys," although not exclusively focused on agroforestry, provides a thorough description of agroforestry in the inhabited valleys and middle uplands of the Marquesas Islands almost a quarter of a century ago.
The islands of the Marquesas are highly eroded, steep, cliffed remnants of ancient submarine volcanoes. The islands lack coastal plains, except at heads of embayments, but possess large habitable, well-watered amphitheatreheaded or elongate canyon valleys, with boulders in tributary beds upstream and rich colluvium in the back-valleys. Recognizable flood plains occur only in the lower reaches of some valleys. In the absence of coastal plains, backvalley colluvial slopes are the most naturally productive areas and the mainstay of Marquesan agroforestry activities. Because of the steeply sloping nature of the islands, severe erosion threatens unvegetated areas. The two valleys studied in detail by Decker, the relatively wet Puama'u valley on Hivaoa Island and the relatively arid Vaipaete valley on Uahuka, illustrate the range of Marquesan lowland environmental conditions (Decker 1971, 9-31).
Population densities were, until recently, relatively low because of widespread post-European-contact depopulation last century owing to disease and outright slaughter. Population has increased, particularly since World War II, although continued out-migration to Tahiti, New Caledonia, and France has kept populations relatively small. None the less, long human occupation has led to the extinction of many species and the substitution of a largely alien flora for the indigenous flora (Decker 1971, 31), with habitual burning being responsible for Miscanthus tall grasslands and Cleichenia fern lands in upland areas (Decker 1971, 95).
Marquesan agroforestry as a land use can be divided into five zones:
Strand-side and wetlands
Bayshore areas are dominated by vast stands of coconuts with other useful large trees such as breadfruit, mango, and kapok. Relict large trees such as Barringtonia asiatica, Calophyllum inophyllum, and Terminalia catappa, formerly useful to the Marquesans, but rarely planted today, are also found in foreshore areas (Decker 1971, 110). Other ubiquitous strand species, so common in Kiribati and coastal areas elsewhere in the Pacific, are conspicuously rare here, although many can be found in inland forests. Stream bed or riparian and marshy areas are dominated by thickets of Hibiscus tiliaceus, with Tahitian chestnut (Inocarpusfagifer) also common.
Village areas and home gardens
Marquesan villages are located in valleys at a distance from the shore to reduce risk from tsunami damage with dwellings located along principal paths and occupying discretely bounded yards of various sizes. Village or home-garden agroforestry is characterized by a plethora of exotic plants accumulated during some 1,500 years of human arrivals from over the sea, with the accumulation of exotics having increased considerably since European contact (Decker 1971, 124).
Dominant species include the coconut and breadfruit, with mango and kapok (Ceiba pentandra) being very common, along with the ubiquitous and usually spontaneous and protected beach hibiscus (Hibiscus tiliaceus), which forms a part of the backdrop of every village. Common spreading ornamental shade trees include the rain tree, or monkey-pod (Samanea saman) and the flame tree, or poinciana (Delonix regia), with Albizia lebbeck also present in dwelling areas.
Immediately surrounding dwelling areas in uncared-for places, on the islands of Nukuhiva and Uapou, are extensive monospecific stands of Leucaena leucocephala, serving as the main lowland fodder for horses, which are highly useful and abundant draught animals in the Marquesas and which are rotationally fed on Leucaena in the lowlands and grazed on limited areas of upland pasture and shrub land (Decker 1971, 129).
The village home gardens are a very directly useful kind of agroforestry serving as a source of:
Because such plants must be accommodated along with stray animals and children, they are usually hardy, thus favouring trees and tree-like shrubs. Less hardy shrubs and colourful herbs are commonly planted against the house beneath the eaves, with hardier shrubs and trees scattered elsewhere, particularly along borders delineating home-garden boundaries.
The most common staple plants in villages and home gardens are coconuts, breadfruit, and banana cultivars, with important fruit-trees including mango, papaya, lime, avocado, soursop and sweetsop (Annona muricata and A. squamosa), guava, and tamarind. Sugar cane is also common in home gardens.
Tree-like shrubs most commonly planted alone borders include Polyscias guilfoylei, Hibiscus rosa-sinesis, and Gardenia taitensis. All are important ornamentals, with the latter highly favoured for its fragrant flowers, which are used in garlands and for scenting coconut oil. Other trees and shrubs with fragrant flowers or of ornamental importance include the perfume tree or ylangylang (Cananga odorata), bougainvillea (Bougainvillea spectabilis), croton (Codiaeum variegatum), cordyline (Cordyline fruticosa), and the coral hibiscus (Hibiscus schizopetalus). The cultivated pandanus (Pandanus tectorius var. Iaevis), so important in the production of plaited ware, and kapok (Ceiba pentandra) are also common in home gardens (Decker 1971, 141-142).
Where households border streams, hardy useful species, both spontaneous and planted, include Hibiscus tiliaceus, Tahitian chestnut (Inocarpus fagifer), coconuts, kapok, and guava (Psidium spp.). Also found in home gardens are a wide range of non-tree, mostly ornamental, species, but also including staple ground crops, such as taro (Colocasia esculenta), tannia (Xanthosoma sagittifolium, known locally as tarua), and the ubiquitous pineapple (Ananas comosus). Also present is giant taro (Alocasia macrorrhiza), or kape, a staple in western Polynesia and a famine food elsewhere, but serving only as an ornamental and never eaten today in the Marquesas.
Back-valley or up-valley gardens and grove lands
Back-valley or up-valley agroforestry gardens and grove lands are the main sources of Marquesan subsistence and commercial production. With rapid population increase since World War II and recent coconut-planting subsidies, gardens and grove lands, particularly coconut plantings, have expanded into extensive back-valley areas of old fallow forest, much of which remains from agroforestry activities prior to widespread depopulation in the Marquesas during the nineteenth century.
Back-valley agroforestry activities provide:
Marquesan agriculture or horticulture has remained remarkably Polynesian in character, being based on intercropping of long-lived root crops with trees that are mostly vegetatively propagated. The system favours the survival of trees and perennials because of its emphasis on diversity and variety rather than maximum yield, the extensive application of labour in terms of weeding and crop care, and the propensity to intercrop old gardens or clear new land when yields decline. Throughout all Marquesan operations having to do with plants there is an emphasis on the care, protection, and utility of individual plants, rather than on the crop or yield of an entire field or planted stand of trees. Consequently, the word "horticulture" is used advisedly to highlight that emphasis.
For the clearing of new gardens, wooded localities are always preferred because ground preparation is less laborious in the shade where weedy undercover is little developed and soil structure is generally loose. Old fallow areas dominated by Hibiscus tiliaceus are seen as the best sites for gardens, although Xylosma-Sapindus forest and transitional thickets are commonly cleared in drier areas. Edaphic requirements influence site selection, with bananas being planted in wetter alluvial sites, often in sheltered ravines, and cassava higher upslope in lighter soils up to the practical limit of cultivation on slopes up to 30° (Decker 1971, 164).
More permanent difficult-to-clear groves of trees such as Ficus prolixa, Mangifera indica, and Inocarpus fagifer are seldom cleared. In garden clearance, small additions to existing gardens are generally hacked out of the fallow vegetation at almost any time of the year, with Hibiscus tiliaceus being cleared and Ficus prolixa and mangoes generally burned at the base and pruned or pollarded, but left remaining to live in garden sites. After firewood has been saved and temporary shelters of Hibiscus tiliaceus poles and coconut thatch prepared, most areas are burned, although sometimes debris is left to rot in place.
The fallow forest is dominated by many species once of great subsistence utility to Marquesan society. The trees have been spared because they retain some use or because people see them as possessing traditional interest. Marquesan horticulture accepts their presence in gardens as readily as it does large old trees and bulky boulders, thus enhancing the variety and bounty of the new garden. The most common species in this category include the ubiquitous Hibiscus tiliaceus, coconuts, breadfruit, and mangoes, with other useful species spared during garden clearance including papaya, coffee, Tahitian chestnut (Inocarpus fagifer), banyans (Ficus prolixa), candlenut (Aleurites moluccana), Malay apple (Syzygium malaccense), guava (Psidium spp.), beach almond (Terminalia catappa), and Fagraea berteriana, plus a range of coastal strand species.
The persistent dominance of ocean-dispersed coastal strand species in Marquesan secondary forests is remarkable in light of Egler's (1939, 45-46) findings that such plants are poorly adapted for terrestrial migration. The major trees or tree-like plants that fall into this category are Hibiscus tiliaceus, Pandanus spp., Erythrina variegata, Cordia subcordata, Guettarda speciosa, Morinda citrifolia, Premna serratifolia, Sapindus saponaria, Cerbera manghas, and Thespesia populnea, all of which seem to regenerate well and are widely naturalized in inland localities. Other species that occur rather sporadically in old fallow forest or adjacent to suspected former habitation sites included Barringtonia asiatica, Calophyllum inophyllum, Terminalia catappa, and Cocos nucifera, most of which are encountered in fallow forests below 500 metres, with the exception of Hibiscus tiliaceus and Pandanus tectorius, which extend up to the cloud forest. Although illadapted to terrestrial dispersal, all these species possessed utility in the aboriginal economy, which argues strongly for their human carriage inland, a dispersal that would have been reinforced by profound human disturbance of the indigenous vegetation below the cloud zone.
The presence of large inland tracts of old forest fallow can be attributed to internecine warfare before and after European contact. These conflicts led to the retreat of gardens to steeper, secure backvalley slopes. Their persistence, today, in fertile inland valleys reflects the widespread abandonment of pre-1800 subsistence groves after drastic depopulation and a changing settlement pattern, with the abandonment of back-valley dwellings in favour of new coastal villages around foreigners' buildings near bay anchorages and mission dwellings (Decker 1971, 90, 72).
The great plant diversity within garden successions in garden and grove areas results from diverse planting and clearance strategies, all of which minimize toil in the long run. Once a new clearing is planted, soil and plant cover are only minimally disturbed, with minimum tillage with digging sticks or mattocks being used to plant new crops, and weeds being cleared by machete, thus maximizing soil protection against erosion, leaching, oxidation, and the depletion of organic material.
In terms of new garden development, perennial arborescent crops such as coconuts and bananas are sometimes planted in the fallow forest before clearance. When the fallow is finally cleared, if these trees have set little foliage, the debris is burned; otherwise, it is allowed to rot and cleared periodically around the bases of the trees. This practice seems to be followed primarily by individuals planting large areas of coconuts in response to the drive to expand copra production. As a result, it is common to see plantings of immature coconuts only a few years old in areas well along with fallow regrowth. Although perhaps detrimental to optimum growth of coconuts' such a multi-purpose agroforestry strategy is a productive compromise between the aims and resources of both administration and individual Marquesans, providing an investment in future production and being conservative of soil fertility. The fallow vegetation can be recleared slowly, a practice that allows labour input to be spread over time.
After the fallow has been cleared and burned, the staple root crops and various short-lived crops are established, together with a range of banana and plantain cultivars (Musa cultivars) and the less common fe'i banana (Musa troglodytarum), breadfruit, coffee, oranges, avocado (Persea americana), and sugar cane. The garden lasts for three or four years, after which it becomes a grove dominated by trees, aborescent herbs (mainly banana cultivars), and palms, with breadfruit, citrus, and coffee beginning to bear. Bananas and fe'i (huetu) bananas form discrete dense groves. Cassava still persists in the fallow as a source of planting material, with Xanthosoma and giant taro also prevalent, their leaves being used to wrap food. Regularly spaced coconut palms, which have not yet begun to bear, are the only evidence of geometric order. Among the thickening canopy, there remains some spontaneous growth of Commelina diffusa and Oplismenus composites as horse fodder, with a few papayas, chillis, guavas, and Morinda citrifolia, which have been spared, still persisting in some areas. In the few open areas, some grasses, herbs, and shrubs persist (Decker 1971, 188-190).
Of note is the abundance of papaya seedlings in areas recently cleared of fallow, especially Hibiscus tiliaceus fallow. Because of papaya's abundance, it is rarely deliberately planted and is not considered a primary human food, but is fed mostly to animals such as pigs, chickens, and dogs. Other pioneering weeds, such as Commelina diffusa and Oplismenus composites (this latter species occurring in abundance only on the island of Uahoka, where very few alien weeds had become established by the 1960s), are highly valued as horse fodder, as new gardens are among the few places where tethered animals can graze in lowland areas while farmers work in the field. Other weedy species, such as the perennial chill) (Capsicum frutescens), are spared, although shoots of Hibiscus tiliaceus, Morinda citrifolia, and Psidium spp. are usually suppressed by slashing in the early stages of gardens.
Arboreal species, either planted or protected, that persist in backvalley gardens and grove lands include fruit-trees, such as pomelo (Citrus grandis), Malay apple (Syzygium malaccense), hog plum, or Polynesian vi-apple (Spondias dulcis), Inga edulis, mango, Psidium species, and Iychee (Litchi chinensis); other utilitarian species present are pandanus, kapok (Ceiba pentandra), perfume tree (Cananga odorata), Coffea arabica, Tahitian gardenia (Gardenia taitensis), and a range of hibiscus cultivars (Hibiscus rosa-sinensis, H. schizopetalus, and ornamental hybrids). Aleurites moluccana, Canthium barbatum, and Thespesia populnea are found occasionally.
Productive fallow areas and mature groves
As garden groves begin to mature and coconut palms start to bear, some seven to ten years after original clearing, production shifts to copra from food, fibre, leaf, and fodder production, and groves take on a character that may persist for decades. Discrete groves of bananas and fe'i bananas (Musa troglodytarum) and breadfruit still produce in favoured sites, and family groves of Tahitian chestnut (Inocarpus fagifer) remain along with occasional remnant Xanthosoma plants. Sometimes, a new tree is added to an ageing grove. The area around individual coconut palms is generally kept free of high growth by slashing with machetes during the search for fallen mature nuts. Further clearing is brought about by the burning of husks, fallen fronds, and other debris during the extraction of the coconut meat, and the tethering of horses to graze the marginal pasture around each tree (Decker 1971, 195-196).
As coconut groves expand at the expense of old fallow forest and more diversified agroforestry activities, the burden of weeding and brush cutting increases and is made more difficult by the invasion of harder-to-clear shrubby weeds such as Indigafera suffruticosa and Ocimum gratissimum, which make collection of nuts more difficult. The mature grove will eventually consist of the remnants of the original fallow forest, planted trees, and pioneering trees such as several varieties of Hibiscus tiliaceus, Morinda citrifolia, guava (Psidium guajava and P. guineense), mango (Mangifera indica), and kapok (Ceiba pentandra), which exhibits phenomenal reproductive ability in some areas, with some "fallow" forests consisting entirely of tall coconut and kapok trees (Decker 1971, 200).
It is difficult to distinguish advanced stages of matured garden groves from old fallow forest, some areas of which have probably re mained out of cultivation for 100 years or more. Although Hibiscus tiliaceus and Inocarpus fagifer dominate old fallow forests in most back-valley ravines and canyons, harvestable coffee is found naturalized in many, and large banyans (Ficus prolixa), Aleurites moluccana, Terminalia catappa, and Spondias dulcis also remain in these areas. In drier areas of old fallow forest, I. fagifer becomes uncommon, with H. tiliaceus becoming the dominant along with scattered individuals of Canthium barbatum, Glochidion sp., Wikstroemia foetida, Morinda citrifolia, Piper latifolium, and Pipturus argenteus, with coffee flourishing and vanilla occurring occasionally as escapes. Discrete groves of bamboo (Schizostachyam glaucifolium) and mango are also found in areas of old fallow forest. Of particular importance are the widespread fallow groves of a vegetatively propagated sterile form of Hibiscus tiliaceus (H. tiliaceus var. sterilis), which was possibly an aboriginal cultigen because of its wide utility in construction and for fruitpicking poles (Decker 1971, 258-262).
In transitional or drier areas, where vegetative growth is slower, back- or up-valley gardens are maintained for longer periods of time, interspersed between uncleared areas of mid-slope forest dominated by Pandanus tectorius, Sapindus saponaria, and Xylosma suaveolens. The crops are essentially the same, although woody perennials including Canthium odoratum, Capsicum frutescens, Carica papaya, Ficus prolixa, Hibiscus tiliaceus, Morinda citrifolia, Cerbera manghas, Premna serratifolia, Psidium spp., Sapindus saponaria, and Xylosma suaveolens, are generally spared in the clearance for new gardens or protected in garden regrowth (Decker 1971, 206). On exposed uplands and ridge tops Casuarina and Pandanus groves, Miscanthus floridulus and Tricholena rosea grasslands, fern scrub lands, and scattered forest stands and thickets exist, along with occasional thickets of Hibiscus tiliaceus in more humid areas (Decker 1971, 231-232).
Thickets in transitional areas include, most commonly, Psidium guineense, P. guajava, Celastrus crenatus, Colubrina asiatica, Premna serratifolia, and Morinda citrifolia, all of these, even C. asiatica, approaching tree stature. Scattered in the widespread Miscanthus (kokaho) grasslands, which have been maintained by periodic burning since pre-European-contact times, are a number of tree species, including, most prominently, Psidium spp., as well as Morinda citrifolia, Celastrus crenatus, Pandanus tectorius, Hibiscus tiliaceus, Xylosma suaveolens, and Casuarina equisetifolia. The forest on lower canyon slopes is dominated in most areas by Xylosma suaveolens and Sapindus saponaria, which give way to Hibiscus tiliaccus in the wetter areas or to coconut groves on the lower slopes. Forests in the valley ravines and bottoms in the transitional zones include the common Sapindus saponaria and Xylosma suaveolens, as well as Hibiscus tiliaceus, Thespesia populnea, Erythrina variegata, Pisonia grandis, Pandanus tectorius, Morinda citrifolia, Canthium odoratum, Premna serratifolia, Aleurites moluccana, and occasionally Celtis pacifica, and Cordia subcordata, with large banyans (Ficus prolixa) as common large emergents. Also appearing sporadically in ravines and valleys are planted or spontaneous economic plants such as chillies (Capsicum frutescens), and kapok, orange, and coconut trees (Decker 1971, 244 245).
Most of the same species, with the exception of Cordia subcordata, Celtis pacifica, and Pisonia grandis, which are absent or uncommon away from the coast and valley bottoms, are also found in transitional forest on upland slopes and inland ridge crests, with Xylosma suaveolens and Sapindus saponaria being the co-dominants, except where the latter has been exploited for firewood for bakers' ovens. Species also found in ridge-crest areas include Glochidion sp., Canthium barbatum, Coffea arabica, occasionally Cocos nucifera, and Mangifera indica; the more frequent occurrence of Hibiscus tiliaceus; and discrete groves of Pandanus tectorius and Casuarina equisetifolia (Decker 1971, 246-252).
In the more arid zones, arborescent plants are more restricted to relict forest stands in the interior and in well-watered and sheltered ravines, with shrubby species (such as Indigofera suffruticosa) and Leucaena leucocephala invading extensive inland areas and coastal areas. Acacia farnesiana, although not invasive, persists in some areas. Other shrub and tree species found in non-garden areas include Gossypium barbadense, Jatropha gossypifolia, Cordia lutea, Tamarindus indica, and Albizia lebbeck, the latter two being occasionally planted (Decker 1971, 214-215).
Open woodland stands of Sapindus saponaria are common, with other tree species in arid areas including Celastrus crenatus, Celtis pacifica, Syzygium spp., Guettarda speciosa, Morinda citrifolia, Psidium spp., and Thespesia populnea. In areas denuded by goats, solitary banyans (Ficus prolixa) are occasionally found.
The most aggressive of the exotic plants and one of the most difficult to clear for new gardens is Leucaena leucocephala, which is controlled in some banana, cassava, and tannia gardens by deliberately planting cuttings of another aggressive weed, Commelina diffusa. After original Leucaena clearance, this weed retards further regen eration, at the same time providing valuable easily-cleared fodder for the ubiquitous horse. This is, however, not a practice in gardens with spreading ground crops such as sweet potatoes and melons, which thrive on clear cultivation and would suffer from competition from Commelina diffusa. Where Leucaena has become established, the tenacious stands seem to exclude all groundcover of other species, with little or no tendency toward succession by native or indigenous trees.
The non-arable uplands, which are dominated by Gleichenia linearis fern lands, with scattered Casuarina equisetifolia and Pandanus tectorius, are found on the deep, degraded latosols of the upland interfluves. Along with the Miscanthus floridulus grasslands, these apparently pyrogenic and fire-maintained areas serve as important seasonal grazing areas covering most of the interfluvial terrain.
The humanized forest of the Marquesas
The close examination of Marquesan plant cover offered here reveals yet again the intense humanization of many Pacific Island landscapes. Looking at the Islands' often extensive forest cover, the uninitiated would be likely to assume that the forest was largely natural, punctuated here and there by gardens or grassy ridges - a land waiting for development. Instead, the forest - much of which is a human artifact is intricately linked to the inhabitants' production of food, materials, and cash crops. The individual trees are the wheels of the forest factory, turning out a great variety of products while also working slowly together to enhance the future productivity of garden soils and to help maintain the present stability of slopes and the clarity of streams. The efficiency of this "factory" could in many instances be improved; its human managers may make mistakes; hard-to-manage components, like Leucaena, may get introduced; none the less, a forest "factory" is already operating in place. It would be useful in planning for the future welfare of land and people to recognize this factory's existence and its significance, before dismantling it under the false impression that it serves little purpose and has no connection with human activities.