Analysis of Monsoon Climate Variability for Swidden Agriculture in Northern Laos

Abstract

Most rice fields in Laos are rain-fed, so crops depend on rainfall amount. Especially in the north, upland rice is grown under swidden agriculture, which is affected by weather conditions in the rainy (monsoon) and pre-monsoon seasons. During the pre-monsoon season, trees and plants are cut and dried to enrich soil before rice planting. However, heavy precipitation during this period disturbs the drying, and is thus unsuitable to initiate burning. Furthermore, climate change, which alters rainfall (wet, normal and dry) and hampers determination of the optimal time of paddy planting, has recently become a problem. Prediction of monsoon season onset is essential for examining influences on the amount of and fluctuations in rainfall. This study investigates rainfall characteristics during the pre-monsoon and monsoon seasons around Kachet village in northern Laos. We diagnose climate impacts on local livelihoods via comparison between rainfall data and results of field survey interviews in the village, to compare actual recognition of villagers and objective data. In the pre-monsoon season, precipitation increased slightly over 47 years, and variance in precipitation tended to increase with a steeper slope than that observed for amount of precipitation. This suggests that weather in this season became unstable and precipitation prediction more difficult. A recent trend of early rainy season onset and increased precipitation has affected the livelihoods of people in the village. The villagers have long engaged in various agricultural activities, based on traditional knowledge. Although knowledge has been accumulated over many generations, it may not accommodate recent climate change.