Population pressures play less of a role in deforestation
than earlier studies of Thailand found.
Between 1976 and 1989, Thailand lost 28 percent of its forest cover. To analyze how road building, population pressure, and geophysical factors affected deforestation in Thailand during that period, Cropper, Griffiths, and Mani develop a model in which the amount of land cleared, the number of agricultural households, and the size of the road network are jointly determined.
The model assumes that the amount of land cleared reflects an equilibrium in the land market. Hence, in the long run, the amount cleared depends on the profitability of agriculture and on the long-run costs of clearing. The size of the country's agricultural population, as well as the size of the road network, affects the demand for cleared land and hence the amount cleared in equilibrium.
The authors estimate an equation to explain the amount of land cleared in equilibrium, using data for the 58 provinces that were forested in 1973. Data from five years (1976, 1978, 1982, 1985, and 1989) are combined to estimate the equilibrium model.
They find that the number of agricultural households and road density both increase the fraction of each provinced cleared, but their effects are small. The elasticity of cleared land with respect to agricultural households is only 0.12; with respect to road density, it is only 0.26.
These effects do differ by region, however; moreover, the elasticities of forest area with respect to population density and road density are larger in absolute value than the respective elasticities for cleared land. The elasticity of forest-to-total area with respect to population density is -0.41 for the North/Northeast section of the country and -0.22 for the South/Central region. The corresponding elasticities with respect to road density are -0.20 and -1.09.
This suggests that population pressures play less of a role in deforestation than earlier studies of Thailand found. For an area to remain deforested, it must be profitable to convert the land to another use, and that use is usually agriculture. Steep slopes and poor soil quality provide some natural protection for forests, although the quantitative impact of those factors vary. Variations in agricultural prices also affect the amount of deforestation.
This paper — a product of the Environment, Infrastructure,
and Agriculture Division, Policy Research Department — is part
of a larger effort in the department to understand the forces
affecting land use change. The study was funded by the Bank's
Research Support Budget under research project "Population
Growth and the Environment" (RPO 678-59). Copies of this
paper are available free from the World Bank, 1818 H Street NW,
Washington, DC 20433. Please contact Anna Marie Marañon, room
N10-031, telephone 202-473-9074, fax 202-522-3230, Internet address
amaranon@worldbank.org. (48 pages)
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