Agricultural Settlement and Land Use in Mountains - Mountain Geography: Physical and Human Dimensions - page 550

can impose limits on human distribution. The highland tribes of New Guinea, for ex-
ample, depend almost completely on the sweet potato or kau kau ( Ipomoea batatas ).
Over 100 language groups occupy the high altitudes of this region, with population
densities reaching up to 500 people per km 2 (1,300 per mi 2 ). This is a sharp contrast
to the sparsely populated and isolated lowlands of the Sepik and Fly Rivers, where an-
nual flooding, insects, malaria, and persistent heat and humidity complicate life. The
highlanders practice a subsistence hoe culture, supporting themselves through intens-
ive cultivation of active and fallow fields (Fig. 11.7). Fenced plots prevent incursions by
pigs, which otherwise roam free. In the more accessible farms along the central high-
way, coffee and vegetable cash crops flank the sweet potato. The dependence on just
one or two crops and the inability to store produce beyond a few days mean that the
people consume food soon after harvest. Thus, growing conditions must be continuously
favorable throughout the year, because interrupted production begets chronic food in-
security (Boyd et al. 2001).
FIGURE 11.6 Stepped rice terraces in northwest Vietnam, near the frontier with China. (Photo by S.
F. Cunha.)
Shifting Cultivation
Shifting cultivation (also known as swidden, ladang, and milpa ) is common in remote
portions of northern Thailand, Borneo, the eastern Andean foothills above the Amazon,
Papua New Guinea, West Africa, Central America, the eastern Himalaya, and northern
Myanmar, Vietnam, Cambodia, and Laos. It is particularly common in areas where lime-
stone weathers into an infertile soil. Shifting cultivators the world over share common
geographic traits: rugged terrain, isolation from markets and population centers, and a