Sustainable Agriculture and the Environment in the Humid Tropics

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Sustainable Agriculture and the Environment in the HUMID TROPICS

ecologic aspects of land use change. Therefore, the most recent models of land use integrate a variety of aspects of land use change so that the causes of deforestation and its impacts can be evaluated.

Models that Integrate Socioeconomic and Ecologic Aspects of Land Use Change

Given the socioeconomic forces that frequently initiate land use changes and, as a result, that cause major ecologic effects, modeling of the land use change process requires models that combine socioeconomic and ecologic factors.

FACTORS AFFECTING LAND USE CHANGES

Grainger (1986,1990b, In press) has argued that land use changes can be attributed to three sets of underlying causes: socioeconomic factors, physical environmental factors, and government policies. It is assumed that national land use morphology (the relative proportions of different land uses, each with different biomass, productivity, and sustainability characteristics) changes over time in response to these underlying causes, each of which is described here briefly. Land use also has a role linked to the degree of sustainability and other factors (discussed later).

Socioeconomic factors, such as population growth and economic development, are the key driving forces causing large areas of forestland in the humid tropics to be transferred to agricultural uses. Rising populations require more land for settlement and crops to supply the increasing demand for food. Growing population densities also lead to more intensive farming practices. National population growth rates are somewhat correlated with deforestation rates in the humid tropics (Allen and Barnes, 1986; Grainger, 1986).

In terms of agriculture, economic development increases per capita food consumption and the need to grow export cash crops. Crops that are grown for export earn foreign currency, which funds continued economic growth. Both trends lead to more deforestation and, assisted by the improved access to Western technology that comes with economic development, to more chain saws, tractors, and other mechanized equipment that increase the rate at which forests can be cleared or damaged. At the same time that economic development catalyzes the spread of deforestation, however, it can also control it, by providing a greater opportunity to invest in improved agricultural techniques and technologies (for example, high-yielding crop varieties) that can grow the same amount of food on a smaller area of

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