El Nino-Southern Oscillation Impacts on Rice Production in Luzon, the Philippines

This study uses regression analysis to evaluate the relationships among sea surface temperature anomalies (SSTA) averaged over the Nino-3.4 region (5 degrees N-5 degrees S, 120 degrees-170 degrees W), rainfall, and rice production, area harvested, and yield in Luzon, the large island on which most Philippine rice is grown. Previous research on Philippine rice production and El Nino-Southern Oscillation (ENSO) has found negative associations between El Nino events and rice yields in rainfed systems. This analysis goes further and shows that both irrigated and rainfed ecosystems are impacted. It also compares impacts on area harvested and yield. Variations in average July-September Nino-3.4 SSTAs explain approximately 29% of the interannual variations in the deviations of total January-June (dry season) rice production from a polynomial trend for 1970-2005. In contrast, no impact was found on July-December production in either year t or t + 1. The impact of ENSO on dry-season rice production in Luzon appears to be primarily due to changes in area harvested rather than yield. Production declines for rainfed ecosystems are relatively larger than for irrigated ecosystems: a 1 degrees C increase in average July-September Nino-3.4 SSTA is associated with a 3.7% decrease in irrigated dry-season production but with a 13.7% decline in rainfed dry-season production.