Roads, population pressures and deforestation in Thailand, 1976 - 1989

Roads, population pressures and deforestation in Thailand, 1976 - 1989

Population pressures play less of a role in deforestation than earlier studies of Thailand found. Between 1976 and 1989, Thailand lost 28 percent ofits 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 whichthe 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 longrun costs of clearing. The size of the country'sagricultural 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 provincesthat were forested in 1973. Data from five years (1976, 1978,1982, 1985, and 1989) are combined to estimate the equilibriummodel.

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/Northeastsection of the country and 0.22 for the South/Central region.The corresponding elasticities with respect to road density are0.20 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 protectionfor forests, although the quantitative impact of those factorsvary. 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 partof a larger effort in the department to understand the forces affecting land use change. The study was funded by the Bank'sResearch Support Budget under research project "PopulationGrowth and the Environment" (RPO 67859). Copies of this paper are available free from the World Bank, 1818 H Street NW,Washington, DC 20433. Please contact Anna Marie MaraÏon, roomN10031, telephone 2024739074, fax 2025223230, Internet addressamaranon@worldbank.org. (48 pages)

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