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| Tuesday, 4 May 2004 |
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Was the bumper rice harvest for 2002/03 Maha due to El Nino? by Lareef Zubair and Ruvini Perera, International Research Institute for Climate Prediction, Earth Institute at Columbia University, New York. And Suganda SomasunderaUniversity of Peradeniya, Peradeniya.
There was a bumper rice harvest for the last 2002/03 Maha season leading to celebration on the one hand, but it has left farmers with the problem of obtaining a poor market. Our policy makers are left to wonder whether this bumper harvest shall be sustained or whether it is an one-off phenomenon so that they can alter their policies. Indeed in 1982/83, after three decades of sustained increases in rice production, there was a bumper harvest in both Yala and Maha seasons and several subsidies such as fertilizer were reduced. During the last five decades, the national rice production has systematically increased due to factors such as high-yielding seed varieties, increased fertilizer application, increases in land under cultivation and use of tractors. Along with this trend, there is also a year to year variation in harvest primarily due to rainfall variations. An analysis of these year to year variations of harvests shows that by and large during the global El Nino climatic episodes, the Yala harvest decreases and the Maha harvest increases. This may indeed have been the cause of the rise in rice production last Maha as an El Nino persisted through it. The term El Nino was coined by fisherfolk a century ago to describe the unusually warm waters that would occasionally form along the coast of Ecuador and Peru. This phenomenon typically occurred late in the calendar year near Christmas, hence the name El Nino (Spanish for "the boy child", referring to the Christ child). Today the term El Nino is used to refer to a broader global scale phenomenon associated with changed oceanic and atmospheric states in the tropics. The Pacific is a large ocean and changes in its surface temperatures affect other tropical regions through an atmospheric "bridge". Just as much as there is a land-sea-breeze day and night because of contrasts in heating rates of the land and oceans, there are east-west patterns of circulation caused by the successive lay out of oceans and continents as one follows the equator. It is this circulation pattern that is affected by the warm Pacific and which in turns affects Sri Lanka on the other side of the world! La Nina is the opposite phase of the El Nino and is characterized by cooler than normal SSTs across much of the tropical eastern Pacific. A La Nina event often, but not always, follows an El Nino vice versa. Once developed, both El Nino and La Nina events tend to last for roughly a year although occasionally they may persist for 18 months or more. The time between successive El Nino events is irregular but they typically tend to recur every three to seven years. El Nino and La Nina are both a normal part of the earth's climate and there is recorded evidence of their having occurred for hundreds of years. During El Nino episodes, there is usually an increase in rainfall over Sri Lanka from October to December at the start of the Maha season and an increase in rice production. In certain, the rainfall was so heavy that there were floods so that production got disrupted. Factors such as war, sudden changes in fertilizer policy and a hike in the previous seasons harvest can influence the rice production along with climate. Not every El Nino results in an increase in rainfall at the planting season and it is only the most important of several global climatic factors that influences Sri Lanka's climate. During the Yala, the rainfall is below average during El Nino episodes. Since Yala is a water-constrained season and only half the land is cultivated. So the impact of rainfall anomalies is felt more keenly and there is a slightly stronger relationship between El Nino. If the La Nina lasts through both a Maha and a Yala then the combined rice production tends to drop in Sri Lanka as the Maha harvest is about twice that of Yala. Overall, we found that this relationship between El Nino/La Nina and rice production held for 33 of the 47 seasons where either of these phases were present in the 92 seasons between 1952 and 1997. A majority of the 24 seasons in which this prognosis was incorrect were seasons in which non-climatic factors influenced the rice production. For a betting person, the odds are favourable for the use advance knowledge of El Nino events that are now available up to nine months for agriculture. Using seasonal climate predictions is not entirely new, as our farmers have anticipated good rainfall historically based such as the dates of arrival of transcontinental migrant birds from China such as the grey wagtail. If the El Nino lasts longer than a year, then the drop in Yala cultivation may be offset by the increase in Maha harvest. Indeed, since the cultivation in Yala is only half as that in Maha, during El Nino episodes, the annual harvest shows only a weak increase. However, this tendency for one season to be more bountiful than the other has important consequence for the livelihood of the farmers, marketing, storage, national policy and historical outcomes. For example, Sirimavo Bandaranaike promised to issue six measures of rice to every coupon cardholder during the 1970 elections. After she was elected she worked hard to increase agricultural production. However during her tenure, the El Nino phenomenon worked against her. There were four years of La Nina during her seven year term and the single El Nino occurred in the wrong season! While one may have gone to the moon by the early seventies, it is still not possible to cool the Pacific to tame the El Nino. This year indeed, an El Nino started in July 2002 and went on until May 2003. Indeed, the agro-meteorologist of the Department of Agriculture, Dr. Ranjith Punyawardhene, who has undertaken pioneering research on this topic, did issue this forecast to extension officers of the Agriculture Department in early October 2002. "According to the last update on the current El Nino conditions issued by the International Research Institute for Climate Prediction, there is nearly 100% chance that El Nino conditions will continue for the remainder of 2002 and up to early 2003. Studies conducted in Sri Lanka have revealed that El Nino events are more likely to cause near or above normal rains during October and November of the Maha season. Thus, it could be safely assumed that prevailing rainy weather may continue... during October-November, 2002." Given the heavy rains that did transpire and the relationships between heavy rainfall and increased rice harvest, it may be prudent to consider that 2003 Maha bumper crop was indeed due to the El Nino event. The El Nino has abated now and it has lapsed into neutral conditions now. After the subsidies were reduced after the bumper harvest in 1982/83 (which was again an El Nino year), there was a dramatic drop in rice production the next years. Indeed, the rate at which the rice production increased decade after decade dropped in 1982. There could be several reasons for that such as the ideological reluctance of the then government's foreign mentors to provide subsidies, the reduced emphasis on self-sufficiency and the exhaustion of the so-called Green Revolution and the civil war. In retrospect, the withdrawal of the subsidies after the 1982 was clearly the wrong incentive. Of course, the policy makers were oblivious to the El Nino and indeed it was 1982 that the first research paper on the relationship between Sri Lankan rainfall and El Nino was published. Shortly thereafter they reversed their decisions but at tremendous cost. Two decades later, we should not repeat that mistake. |
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