| Agroforestry in the Pacific Islands: Systems for Sustainability (1993) |
|5 Agroforestry in Polynesia|
A note on Polynesia
Although the agroforestry systems of the smaller, more geologicallyrecent islands of Polynesia are in many ways similar to those of the larger, more heavily forested islands of Melanesia, there are significant differences. Little truly native forest remains in Polynesia, agricultural cycles have shortened, there are generally fewer tree species, and agrodeforestation is more widespread, both in terms of the elimination of trees and forest stands and the failure to protect or replant trees in active agricultural areas. The main causes of these processes are the comparative scarcity of land, rapid population growth on some islands, habitual burning, the increasing use of land for monocultural commercial agricultural production or non-agricultural purposes, and a loss of appreciation of the importance of trees among the younger generation. However, as the four Polynesian case-studies illustrate, great variation remains in Polynesia, with very rich agroforestry traditions present in areas such as Tonga and Rotuma, whereas at the other extreme - as in Aitutaki, in the Cook Islands agrodeforestation has proceeded to a dangerous stage.
Although similar agroforestry zones are found in Melanesia and Polynesia, very little primary or relatively undisturbed forest remains in Polynesia, and what natural forest there is has always been floristically less diverse than that in Melanesia. In Polynesia, the dominant vegetation communities consist of coastal strand and, in some cases, mangroves, isolated relict stands of tropical lowland or upland forest, mature fallow forest, highly degraded fire-climax communities rarely used for agriculture, and the much modified communities and fallow vegetation found in active agricultural areas, villages, and towns.
Shifting agroforestry remains a widespread practice in well-drained areas, with semi-permanent, sometimes irrigated, Colocasia taro gardens in poorly-drained alluvial lowlands and river valleys, and home gardens in settlements. In the complex systems of Tonga and Rotuma the dominant root-crop staples and a wide range of banana and plantain cultivars are grown in a shifting pattern on land so heavily planted with coconuts, breadfruit, citrus trees, and other trees that most garden areas resemble polycultural orchards. Interspersed throughout garden areas are small groves of secondary fallow forest or bushfallow containing both indigenous and exotic species of great cultural utility. As in the case of Melanesia, coastal strand forest, swamp forest, and mangrove forest are considered integral and useful components of the productive landscape.
Where staple and supplementary food crops continue to be partly derived from and integrated with a matrix of trees, the landscape also contains many important non-food trees or tree-like plants, for example, pandanus cultivars for handicrafts (Pandanus spp.), paper mulberry (Broussonetia papyrifera) for bark-cloth manufacture, and kava (Piper methysticum), the traditional ritual beverage of Polynesia. Most of these plants, which will be further described in the casestudies, are also important in, and probably introduced through or from, Melanesia.
An aspect of Polynesian agriculture that is not so well developed in the areas studied in Melanesia is the increasing, often intensive, monocultural commercial cultivation of non-tree crops, both for export and for the rapidly expanding local urban markets. These crops, most of which also have subsistence value, include water melons, pineapples, peanuts, tomatoes, Chinese cabbage, capsicum, cucumber, and other short-term vegetables, and traditional staples, such as yams, Colocasia and Xanthosoma taros, sweet potato, and cassava. In Tonga, vanilla (Vanilla fragrans) and butter squash (Curcurbita sp.), the latter destined for the Japanese market, have become monocultural components of the system. Vanilla is also produced for export in French Polynesia.
Bananas are grown on an intensive monocultural basis for export in Tonga, Western Samoa, and the Cook Islands, and there are attempts to develop monocultural citrus production for export and local processing in Nine and the Cook Islands. Both bananas and citrus have suffered from continuing problems with pest and disease control, damage from tropical cyclones and high winds, poor management, inadequate quality control, marketing difficulties, and import and quarantine restrictions. Consequently, these crops have been largely uneconomic, and their further development has been highly aid-dependent. The coconut remains the main cash crop for the majority of smallholder agroforesters in Polynesia, whereas the more diversified commercial arboricultures found on the large islands of Melanesia, based on the inclusion of cocoa, coffee, rubber, and oil palm, are largely absent in Polynesia, except in Samoa, where cocoa has been a major cash crop since the time of German occupation. Coffee has been widely tried, with limited production for local consumption in Tonga, Western Samoa, the Cook Islands, and French Polynesia.
Exotic species of post-European introduction that have become integral components of Polynesian agroforestry systems include kapok (Ceiba pentandra), frangipani (Plumeria rubra and P. obtusa), allspice and bay rum (Pimenta doica and P. racemosa), and jambolan (Syzygium cumin)), with leucaena (Leucaena leucocephala) and guava (Psidium gunjava) having become widely naturalized components of fallow vegetation that grow in almost impenetrable monospecific stands on many islands. There are also a number of exotic timber species introduced as part of reforestation schemes; these include Albizia falcataria, silky oak (Grevillea robusta), eucalyptus (Eucalyptus spp.), cigar box cedar (Cedrela odorata), West Indian mahogany (Swietenia macrophylla), and Caribbean pine (Pinus caribaea), which have been planted in small woodlots, as border plantings, or as scattered individual trees.
Home gardens are an important component of Polynesian agroforestry strategies, particularly in areas like Aitutaki and Rarotonga, where agrodeforestation has been extensive. Home gardens serve as refugia for endangered species, as well as avenues for the testing and introduction of new species. Home-garden agroforestry is characterized by a wide range of fruittrees, ornamental trees, and shrubs with fragrant flowers or leaves, and a number of other useful trees that serve as a matrix for lawns, structures, and scattered flower gardens.
Throughout most of Polynesia, continuing official bias toward monocultural export cultivation of citrus, banana, papaya, water melon, tomatoes, and other crops, and on monocultural root cropping, has led to widespread deforestation and agrodeforestation. Concomitantly, polycultural root and tree cropping has declined, existing tree groves have been neglected, and large areas of previously important fallow forests and associated tree species have been cleared. Agrodeforestation and the cultural abandonment of traditionally important trees on Rarotonga and Aitutaki have perhaps been worse than in most areas of the Pacific, although similar trends are evident elsewhere - as in Tonga, where 90 farmers, in a survey of 100 farmers, reported declining numbers of trees on their own fields (Kunzel 1989, 27). If not reversed, such trends could lead to the abandonment of agroforestry traditions that have sustained the highly sophisticated hierarchical societies of Polynesia for many centuries.