Roads, population pressures, and deforestation in Thailand, 1976-89

Tropical deforestation is considered one of the major environmental disasters of the 20th century, although there have been few careful studies of its causes. This paper examines the causes of deforestation in Thailand between 1976 and 1989, a period when the country lost 28% of its forest cover. This paper takes the perspective that, in the long run, the determinants of deforestation are the determinants of land use change. While logging and fuelwood gathering may remove forest cover, regrowth will occur, at least in moist tropical forests. For an area to remain deforested, it must be profitable to convert the land to another use, and this use is usually agricultural. In Thailand, for example, agricultural land increased between 1961 and 1988; during the same period, forest land decreased. This paper focuses on what, in equilibrium, determines the amount of land cleared for agriculture. The authors emphasize the quantitative impact of two forces--roads and population pressures--that increase the profitability of converting forest land to agriculture. As aerial maps show, development follows road networks. The magnitude of the impact of roads on commercial and subsistence agriculture depends on soil quality along the road. In this case the Thailand government undertook a road-building program in the Northeast section in the 1970's to encourage settlement of that region as a bulwark against Communist encroachment from Laos. Road building very likely spurred deforestation in the Northeast during the 1970's and 1980's, although the magnitude of its impact is not known. Thailand also experienced rapid population growth during this same period, which may have contributed to deforestation in two ways: the growing population demanding more food, increased the demand for agricultural land; and more importantly, in rural areas where other economic opportunities are limited and squatters are permitted on forest lands, a growing population increased the demand for land for subsistence agriculture. The authors conclude that population pressures play less of a role in deforestation than was found in earlier studies on Thailand. Affecting the amount of deforestation are other factors, such as the profitability of converting the land to another use, natural protection for forests like poor soil and steep slopes, and agricultural price variations.