In many places now, settlers simply cut and burn the forest to establish permanent cultivated fields or pasture. This type of “slash-and-burn” agriculture has converted huge areas of upland Vietnam into wastelands within the past 30 years. Repetitive burning in the current practice of slash-and-burn agriculture produces many greenhouse gases (carbon dioxide, nitrous oxide, hydrocarbons). More than 1½ million metric tons of carbon per year are released into the atmosphere by these agricultural methods, approximately 23% of the total released by human activities (Kaiser, 1997). In 10 years, almost as much plant material will have been burned in pastureland to clear weeds and stimulate the growth of grass as had been burned initially to create the farm or ranch. Previously, traditional agriculture used small fields and less intensive cultivation, and fields were permitted long fallow periods. Now fields are being reused on very short rotation schedules, so that the forests do not have time to recover, nor is there time for fertility to be re-established. In Vietnam some groups are still using traditional swidden systems, in which the landscape is a mosaic of swidden fields, secondary forest, and older forest. About 84% of the area in Ban Tat (village) is still under secondary regenerating forest or successional vegetation (down from 92% in 1952). However, over the past 50 years, the area covered by closed or open canopy forest has decreased considerably, and the area of scrub and grassland has more than doubled in size. The change has been from primary forest to heterogeneous secondary vegetation, with concomitant fragmentation. Nevertheless, most of the land (except for rice fields in the valley floor) has not been permanently converted to agriculture, nor permanently deforested, but it is on its way (Fox, et al., 2000).

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