Human Ecology, Vol. 28, No. 3, 2000 Impact of Population Pressure on Food Production: An Analysis of Land Use Change and Subsistence Pattern in the Tari Basin in Papua New Guinea Highlands Masahiro Umezaki,1,3 Yukio Kuchikura,2 Taro Yamauchi,1 and Ryutaro Ohtsuka1 The impact of increase in population on land use and subsistence pattern was examined in two environmentally contrasting Huli-speaking communities, Heli and Wenani, in the Tari basin in Papua New Guinea Highlands. Despite the similar extent of population increase in both communities, the damage to land differed markedly. In Heli, a decrease in land productivity owing to exces- sive agricultural use has induced farmers to shorten the fallow duration, which in turn has led to further land degradation and difficulties in increasing food production. In contrast, Wenani villagers have coped with the population in- crease by enlarging areas for cultivation and possibly will be able to double their present production level, although increasingly frequent disputes over land rights have restricted peoples��� access to fertile areas. During a period of climaticperturbationsin1994,landandlaborproductivitiesofcropswerethree times higher in Wenani than in Heli, which suffered a severe food shortage. This difference in ability to cope with climatic perturbations may have in- creased with population growth. The findings in the present study suggest that the effects of population pressure on food production may differ between com- munities, depending on the indigenous environment and subsistence pattern. KEY WORDS: land use population pressure environmental degradation Papua New Guinea Highlands. 1Department of Human Ecology, School of International Health, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. 2Department of Anthropology, Faculty of Regional Studies, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan. 3To whom correspondence should be addressed. Fax: +81-3-5841-3395. e-mail: ume@humeco. m.u-tokyo.ac.jp. 359 0300-7839/00/0900-0359$18.00/0 ��� 2000 Plenum Publishing Corporation

360 Umezaki, Kuchikura, Yamauchi, and Ohtsuka INTRODUCTION Much of the concern about rapid population increase in developing countries reflects fears of insufficiency in local food production (Lee et al., 1988). Despite a growing body of literature on the topic, much of the discussion is based on simplistic notions regarding the relationship between population growth and its consequences for agricultural produc- tion (Uitto, 1995). Most representative is the argument by Boserup (1965) that population pressure might drive farmers to innovate new land use practices and mitigate resource degradation. However, there is an increasingly prevalent view that the processes of change addressed in Boserup���s argument are too gradual to allow communities to cope with rates of population growth now widely experienced (Brookfield, 1995). Furthermore, various factors, such as the physical environment, commercialization, social organization, political change, and subsistence pattern, will be expected to influence the effects of population pressure on agricultural production (Ellen, 1982 Moran, 1990 Allen et al., 1995 Ohtsuka et al., 1998). The Papua New Guinea Highlands, more than 1200 m above sea level, are located in the central part of the country. The population density in the Highlands is higher than in other areas, and recently the population growth rate has exceeded 2% per year. Both historically and particularly in recent decades, overpopulation has been suggested as a fundamental factor in triggering intergroup warfare, rural���urban migra- tion, and environmental degradation (e.g., Vayda, 1971 Harris, 1978 Smith, 1985 Wood, 1985 Kumagai, 1987 Estreguil and Lambin, 1996). It is evident that population increase is one of the most important factors disrupting food security, yet few studies have clarified the relationship between population increase and food production among Highland popu- lations. We aim here to clarify the impact of population increase on food production among Huli-speaking people, a population that has experienced rapid population increase and environmental deterioration in recent decades (Wood, 1985). It should be noted that the data used in this paper were collected in 1994 during an extended rainy period in the Tari basin (Umezaki et al., 1999). Thus, land productivity may have been lower than levels observed during a corresponding period of normal climatic conditions in 1993 (Kuchikura, 1999). However, these conditions allowed us to highlight the deterioration in the food production system and to evaluate the responses of the food production system to climatic perturbations [the importance of the latter is emphasized by Vayda and McCay (1975)].

Impact of Population Pressure on Food Production 361 BACKGROUND Ecological Setting The Tari basin and the surrounding mountainous areas, homeland of the Huli-speaking peoples, are located between 142 45 and 143 10 E longitude and between 5 40 and 6 00 S latitude in the Southern Highlands Province of Papua New Guinea (Fig. 1). The basin consists of two environ- mental zones: swampy flat areas (wet zone) and mountainous slopes (dry zone) (Wood, 1985). The former extend from the Tari airstrip to the south- east and to the swamp along the major rivers, while the latter cover the hilly areas beside uncultivable limestone ridges (Fig. 1). According to esti- mates made by the Papua New Guinea Institute of Medical Research (Lehmann et al., 1997), the annual population growth rate from 1981 to Fig. 1. Environmental zones in the Tari basin and location of the communities studied.