Roles and Impacts of Biomass Burning in Slash-and-Burn Land Use in Tropical Mountains: A Case Study in Laos

摘要

Biomass burning is an essential part of slash-and-burn (S&B) agriculture, which is widely practiced as an important food production system in the tropical mountains of Southeast Asia. S&B agriculture used to be sustainable and carbon neutral; CO_2 emissions by biomass burning were balanced with photosynthetic biomass growth, and land use was stable. However, due to drastic land-use change in the past decades, S&B ecosystems have become a significant source of CO_2 emissions into the atmosphere. The productivity of both land and labor in S&B agriculture has been seriously affected by land-use change. This case study in Laos reveals the reality of the chrono-sequential change in land use and ecosystem management on a regional scale. Not only the area of S&B cropping but also the frequency of biomass burning (and thus the duration of the fallow period) had a strong influence on the ecosystem's carbon stocks and, in turn, on the deterioration of land and labor productivity in crop production. Historically, the indigenous people of this large area have been highly dependent on S&B agriculture for their living. Traditional S&B land use contributes to the sustainabil-ity of forest and water resources as well as to biodiversity. The multiple functions of biomass burning and S&B land use have to be taken into consideration. Feasible land use and ecosystem management options would include alternative S&B land-use scenarios that assure food security as well as carbon sequestration and forest conservation. This paper discusses the multiple functions of S&B land use in the mountains of Laos and presents scientific approaches towards better solutions.