Ecology and the Adaptation of Polynesian Agricultural Systems

(especially Colocasia esculenta). Though the origins of Polynesian agriculture must be sought beyond its geographical borders, the variability in the region's agricultural systems cannot be explained solely with reference to diffusionist theory. A long tradition in Pacific ethnobotany has been concerned with the external origins and routes of diffusion of crop plants to Polynesia (e.g. Merrill 1954, St John 1953, McDaniels 1947, Barrau 1963, Yen 1974), mirroring the parallel preoccupation of anthropologists and prehistorians with the cultural origins of the Oceanic peoples. In recent years, the aims of ethnobotanists and prehistorians both have broadened and coalesced, with a common focus on the processes of agricultural adaptation and development within Polynesia itself. This orientation has been taken up whole-heartedly by archaeologists, who have begun to seek direct manifestations of former cropping systems, and to relate these to the evidence for concomitant developments in technology, settlement pattern, demographic change, and even to * socio-political developments. It is in this broad cultural and environmental context that the variability of Polynesian agriculture will ultimately be explained. Variation in Polynesian agricultural systems exists at a number of levels: in crop plant inventories, extent of agronomic modification of local environment, elaborateness of tool kits, degree of intensification, and so forth. To briefly illustrate this variability, we may contrast several systems (as known at their ethnographic contact 'endpoints') in terms of the relative emphasis each placed upon three major subsystems: (1) swidden, or in intensihec1 situations, dry-field cultivation, generally focussed on Dioscorea, aroids, bananas, and Ipomoea; (2) water-control for the 'wet' cultivation of Colocasia; and (3) arboriculture, centred especially on breadfruit. In Figure 1, the relative emphases placed on these three subsystems is contrasted for seven Polynesian agricultural systems. (Ow ng to the dearth of quantitative d ta on Polynesian agricultural production, this figure is meant only to convey the relative emphasis on maj r subsystems.) These systems range from those of Futuna and 'Uvea, in which all three subsystems contribute substantially to production, to that of Easter Is., dominated by dry-field cropping, or to that of Takapoto (Tuamotu) where pit cultivation of Colocasia and arboriculture centred on coconut dominate. As with the variation in Polynesian social and political systems that have attracted so much anthropological interest, the region's agricultural systems clearly represent a case of 'adaptive radiation' to a variety of natural as well as cultural environments. In the following pages I review some of the processes underlying agricultural adaptation in Polynesia, and cite recent archaeological evidence which has given some concrete manifestation to these processes. Processes which have contributed to the variability of Polynesian agricultural systems may be grouped into three major categories: (1) changes attendant upon initial transfer of systems from one island to another; (2) long-term changes in response to local environmental selection pressures, both spatial and temporal; and (3) changes associated with demographic and sociopolitical influences.