なぜマングローブ林は再生したのか?

――ベトナム、カマウ省ゴックヒエン県の湿地利用制度とインセンティブ――

抄録

From the mid-1980s to the mid-1990s, the mangrove in Ngoc Hien district, Ca Mau province, suffered serious environmental degradation from human activities such as the conversion from mangrove wetland to arable land or to shrimp farming ponds. However, in the years 1994 to 2000, while the population of the area and gross output of shrimp grew, the forest area also rapidly increased. This paper examines why these phenomena occurred by focusing on the role of formal institutions for natural resource utilization.
 The provincial authorities had made several regulations to promote forest since the 1970s, but these had only stimulated local organizations and residents to exploit forests for their own benefit. The formal institutions did not result in collective action based on incentives for forest conservation, particularly after a land allocation policy was applied in the district. The enforcement of land allocation to households imposed costs on local organizations, such as land use investigation and the selection of households for land tenure. Moreover, households then had to invest in preparation for shrimp farming and tree planting on their land.
 Under the national forest conservation program 327-CT, implemented in Ca Mau province in 1993, local institutions were able to fulfill their functions because budget resources created a common interest in forest conservation among local organizations and residents. Moreover, the new Land Law of 1993 permitted households to sell or lease land use rights. This affected forest conservation because preserving trees was a precondition if a household wanted lawfully to sell or lease their land. The increase in forest area in Ngoc Hien district was the result of formal institutions reducing the transaction costs of local organizations and residents.