Agricultural Settlement and Land Use in Mountains - Mountain Geography: Physical and Human Dimensions - page 552

of Laos, for example, as population density increased during the last half century from
2.9-6.8 mi 2 (7.6 to 17.6 persons/km 2 ), fallow periods decreased from 38 to five years
(Roder 1997). Highlanders in Papua New Guinea mitigate this problem by incorporating
compost from short grassy fallow fields into soil mounds, a key that boosted productiv-
ity (Sillitoe 1998).
FIGURE 11.7 A Huli farmer in the Eastern Highlands of Papua New Guinea. (Photo by S. F. Cunha.)
Although shifting cultivation supports at least 300 million people worldwide, it is
slowly declining in tropical mountains. Population pressure in the Mayan highlands
of southern Mexico and Guatemala hurried its demise, as secondary plant succession
in fallowed areas rarely progressed beyond the grassland stage. In these situations,
former cropland is converted to pasture (Brush 1988). The shortened cultivation cycles,
individual farmer choice, expansion of the global road network into formerly isolated
slash-and-burn regions, and government attempts to promote higher-yield farming are