Exploration of spatial and temporal variability of rainfall and their impact on rice production in Burma in 1901–1939 during the colonial period

Abstract

Climate is one of the main factors for rice crop growth. Understanding the relationship between climate variability and rice production during the period from 1901 to 1939 in Burma can give a clear picture of the impact of climate variability on rice yield since there were fewer human interventions on the catchment and almost no use of chemical fertilizer or high-yielding rice varieties at that time. However, the quantitative analysis of climate variability and its impact on rice production has not yet been paid sufficient scientific attention for the historic period. First, the changing trends of rainfall and rice yield between 1901 and 1939 were analyzed, including the effect of rainfall variability on rice production from multiple perspectives regarding rainfall characteristics, such as seasonal rainfall, various rainfall indices, rainfall anomalies, and monthly rainfall variability. Then, the relationship between rice yield and rainfall was investigated using multiple regression analysis to show how rainfall spatial and temporal variabilities have influenced rice yield and production, including essential factors that affected rice yield in each Burma district. The historical development of rice production in Burma during the period was also explored. Our findings indicate that not only the annual variability of rainfall, but also its monthly variability within a particular year likely influenced rice production. Excessive rainfall in the early or middle stage of crop growth or less during the early-middle or latter half of crop growth possibly caused the rice yield reduction in Burma during the colonial period. Furthermore, the results indicated that although rainfall anomalies widely differed from period to period, rice yield anomalies clearly showed the distinction of periods with higher or lower rice yields than average rice yield. Mostly higher than average rice yield was observed before 1910 in the Coastal Zone and before 1918 in the Delta, Dry, and Hilly Zones. The results of this study imply that selected rainfall indices could affect rice yield, positively or negatively, including the varied magnitude of their effects from one district to another, depending on climatic zones and agricultural ecosystems. [Figure not available: see fulltext.]