Taim hangre : variation in subsistence food supply in the Papua New Guinea highlands

Abstract

This research seeks to understand the causes of variation in subsistence food supply in the highlands of Papua New Guinea, particularly the reasons for shortages of sweet potato, the staple food. The study is regional, but the most intensive observations and data are from two provinces and from one community in each of these provinces. Two main indices of subsistence food supply are used: firstly, survey data from food markets and secondly, statements made by villagers about food supply, as documented by outside observers. Particular emphasis is given to long data runs on food availability. Food shortages have an impact on people’s wellbeing. Prior to the colonial period, they resulted in an increased death rate. Body weights of both adults and children are influenced by variation in subsistence food supply. The impact of food shortages is likely to be muted when people have access to cash which they use to buy imported food when subsistence food is scarce. Evidence is brought forward which demonstrates that the frequency of food supply problems has not altered since colonial contact in the 1930s. Activities associated with cash cropping, labour migration or harvesting of a pandanus nut, which are commonly put forward as explanations for food shortages, are eliminated as causal factors. Disruptions associated with pig killing ceremonies and tribal fighting may be contributing factors at times, but their impact is limited. The food production systems in the highlands are sufficiently flexible to absorb short term fluctuations in planting rate and crop yield. Long run rainfall records, market price series and crop planting data are used to demonstrate that the major causes of variation in supply are climatic extremes, particularly extended wet periods and frost, and variation in the crop planting rate. Only the most severe droughts cause food shortages, unless a drought is preceded by an extended wet period. In the latter situation, droughts may become a contributing factor. Wet periods appear to be most damaging when the sweet potato tubers are being initiated and droughts reduce yield during the rapid bulking phase. Frost damage sometimes results in food shortages at high altitude locations, but this is uncommon below 2200 m. Villagers vary their planting rates according to the current supply of sweet potato. They plant larger areas when sweet potato is scarce, and a higher proportion of plantings is then made in fallow land. This behaviour initiates a cycle in planting, similar to the well known "hog price cycle", and this may eventually result in another food shortage, particularly if lower planting rates coincide with a climatic extreme. A model is presented that combines these elements to calculate the supply of sweet potato over a five year period in two locations. The calculated food supply is in good agreement with indices of food availability for the same period.