Effect of El Niño on rice production in the Philippines

The effect of El Niño on national rice production parameters was analyzed by comparing the trends in rice production, rice yields and harvested rice areas for the period 1970-2005 for normal and for all (including El Niño) years. The deviations from the expected national production, yield level and area harvested were computed for rainfed, irrigated and combined rainfed and irrigated areas for each cropping season for weak, moderate and strong El Niño episodes. At the provincial level, the deviations in rice production were regressed against an index of El Niño-induced drought magnitude which was computed as the sum of the percent deviation of monthly rainfall from its normal value for all continuous periods within the cropping season with below normal rainfall lasting 2 mo. or more. The sample provinces were grouped according to the Corona climate types and vulnerability classification of David et al. (2007) to gain insights on the effects of El Niño-induced drought rice production in provinces with different climate types and El Niño-induced droughts vulnerability categories. The results of the analysis showed that the annual growth rate in rice production is linear (0.24 million metric tons/yr). At the present level of rice production, the annual increase in rice production amounted to an annual growth rate of less than 2%. The effect of El Niño on rice production depended on the strength and time of occurrence of the warm episode. During the dry season, strong, moderate and weak El Niño episodes depressed total rice production by about 22%, 6% and 0.2%, respectively. The vulnerability to El Niño-induced droughts of rice production in the sample provinces may be modeled from the resulting regression equations. The relative vulnerability to droughts of other provinces may be gleaned from the average values of the parameters for provinces within the same climate type or drought vulnerability class.