Subsistence Agriculture in Melanesia

The inhabitants in Melanesia which contains the largest island of the tropics, New Guinea, and other larger ones than those in Polynesia and Micronesia, seem more active for agricultural production than in the other regions mentioned above. When we analyze the structure of the agricultural system in Melanesia, it is convenient, just as in the cases of most developing countries in the tropics, to divide it into two sectors, i.e., commercial agriculture and subsistence production. Most of the researchers engaged in the various aspects of subsistence agriculture in Melanesia, which is very often called horticulture conventionally by Westerners, agree on the view that the staple foods of the majority of the inhabitants there have been Colocasia taros and yams since very old times. In some areas, however, the people have been ingesting mostly sago starch or bananas including plantains. Besides these crops, other fruits, such as coconuts and bread fruits, have also been very frequently consumed by Melanesians as well as Polynesians and Micronesians. Talking about the present situation of subsistence agriculture or horticulture in many regions of Melanesia, we cannot disregard the great and growing importance of sweet potato and cassava as the inhabitants' basic sources of food energy. Of these two crops, in some regions, the former has been maintaining the position of staple food from an old or relatively recent time. For example, according to the popular view, more than 300 years have already elapsed since the primary food in the New Guinean Highlands changed from taros and/or yams to sweet potatoes. The data on the basis of FAO sources in the first half of the 1980's elucidated that the leading country for the per capita production of sweet potatoes (193Kg/year) was the Solomon Islands. In that country, however, it was not a very ancient date but around 1960 that sweet potato was considered to become the crop for the staple food of most people there. This is endorsed by many reports having been published since the 1950's. The major and direct reason for the change of the primary crop in the Solomon Islands was the spread, throughout that country, of pathogenic blight-producing fungi and of a beetle pest both of which are specific to taros. In addition to this dilect reason, however, the following circumstances are considered to have certainly related to the preceding change :The penetration and completion of the British governing system which was combined with the permeation of Christianity had become effective in calming down the bloody conflicts between ethnic groups or hamlets and had removed the people's necessity for living in the mountainous areas to seclude themselves from their enemies. As a consequence of such Pax Britannica, since the 1930's, the majority of inland villagers began to move to seek after an easier life in coastal zones to which many mission centres of some Christian sects attracted them by various kinds of benevolent aid which respective missionary groups offered. As predicted logically and naturally from such population movement in an island, the population density in a considerable number of coastal zones was much increased and the fallow periods for most swiddens there were distinctively shortened, even though the average value of population density of the whole of an island increased only slightly. It is said that, to obtain a satisfactory yield of taros or yams, a long fallow period for more than 10-15 years is desirable. When the fallow period for those crops has been shortened to less years than the desirable period, undesirable results leading finally to a marked decrease in the yield and a severe deterioration in the quality of those crops will follow in many cases. On the other hand, sweet potatoes were usually found to be much less affected in this regard than both taros and yams even where the fallow periods were reduced to less than 10 years. Furthermore, attention ought to be paid to the fact that, generally speaking, sweet potatoes provide, of all the food crops in the world, the highest value of land productivity measured in energy units. In addition to the patchy distribution of the population, the rate of increase of the population in all the Solomon Islands jumped up after 1960. This also accelerated the reduction of the fallow periods of the swiddens in that country. It is also notable that the swiddening management for the production of sweet potatoes is much easier and less laborious than for that of taros or yams. Summarizing these respects stated above, sweet potatoes are surely superior to taros or yams concerning labor productivity and security in the sense that the farmers rarely lack their subsistence requirements. This is probably the prime reason why the cultivation of sweet potatoes has become immensely and widely popular in the Solomon Islands from the 1950's. The change of the staple food of the inhabitants there needed a trigger such as the spread of pest and blight but was, however, basically due to changes of social circumstances