Study: El Niño’s Impacts on Water, Agriculture and Health

By Ben Orlove and Ángel Muñoz

A new study examines the degree to which decision makers working in key sectors–agriculture, water and health–have been able to make successful use of forecasts of El Niño and La Niña. We find that these forecasts have indeed often been put into use, but only when two conditions have been met. First, the forecasts must be sufficiently skillful, and also directly linked to a particular sector of public interest. Second, there must be organizations that can act as intermediaries between the scientists who develop the forecasts and the people who will actually put them into use. Without the activities of such organizations, the potential users are unlikely to understand the forecasts and the benefits of using them.

The El Niño-Southern Oscillation, or ENSO, is widely recognized as the most prominent mode of climate variability, operating on time scales of a few months to a few years. It is commonly associated with temperature anomalies in the surface waters of the equatorial Pacific: warmer-than-normal conditions are referred to as El Niño, while La Niña corresponds to colder-than-normal conditions. These anomalies are linked to shifts in pressure systems, winds and rainfall. Through its effect on global atmospheric circulation, ENSO can have profound effects on human societies and ecosystem. It influences extreme events such as drought, floods, and tropical cyclones in many regions of the world, and these conditions can impact agriculture and food security, water resources and health.  Nearly three decades ago, the development of forecasts of El Niño events captured the attention of natural and social scientists, policy makers and resource managers who were eager to see these predictions put to use.

Video Abstract: El Niño-Southern Oscillation and its connections to society

We conducted an extensive review of the use and application of ENSO forecasts. To our knowledge, this is the first time that such an overview has been conducted. We searched the leading database of peer-reviewed articles in all fields of natural and social science, using a variety of terms to refer to ENSO, to decisions, applications and management, and to particular sectors. We then read through the abstracts of all these papers carefully to find the ones that directly discussed the use of forecasts in programs or projects to address the impacts of El Niño. We excluded papers that focused exclusively on the scientific properties of the forecasts.  After this selection, we winnowed the original sample down to 392 documented instances of ENSO forecasts being used. We then analyzed this set of cases. We noted the year of the study, the country or region in which it was located, and the particular economic or social activity that was addressed. We paid particular attention to three sectors—agriculture, health and water management—since these were the ones most widely represented in the published literature. The number of studies for other sectors, such as fisheries, natural hazards and biodiversity conservation, was smaller.

The results of this review documented three patterns. Firstly, forecast use is concentrated in areas in which El Niño has strong effects—in most of the tropics and much of the sub-tropics.   This finding is hardly startling, since people can only use forecasts where forecasts can be made. Secondly, the forecast use began at low levels in the 1990s and has grown since then. This point makes sense too, since many new developments begin slowly and then advance.

The third pattern, however, calls for some attention and explanation. The highest levels of forecast use are in the agricultural sector and the lowest levels in the health sector. Water resources management represents an intermediate level. Water might seem to be the most promising sector for the use of forecasts, since it requires less detailed forecasts, which are easier to produce than more specific ones. A farmer cares about the precise amount of rain in one specific farm, and about the timing of rainfall during the rainy season, while a water manager can make use of forecasts that cover a larger area, and that have low precision about timing within the season. Moreover, water managers often have higher levels of scientific training than farmers, so they should be better able to incorporate the forecasts into their planning.

We argue that the supporting organizations have made the critical difference.  In agriculture, forecast use has been promoted by institutions which farmers trust, including international agricultural organizations, national agricultural extension services, and independent farmers’ organizations. The prior experience of farmers in receiving technical information from these organizations customized to their circumstances is also of importance.  In contrast, water managers are blocked, rather than supported, by organizations. These managers are concerned they would be blamed for any negative outcome that might result from a deviation from normal procedures.   In many settings, water managers are legally responsible for supplying water to users and can be taken to court to justify their actions.  In contrast, farmers may blame advisors or other institutions when forecasts are not borne out, but the political consequences are less severe—in part because of the long experience of farmers in using weather-based technical advice.  In the health sector, where evidence-based policy is strongly promoted, organizations have been slow to promote the use of forecasts.

This study shows that the effective use of climate forecasts by society is growing. It shows that there are two conditions to be met for this use to occur: the forecasts have to be accurate and the society has to have organizations committed to the promotion of forecast use. It is encouraging to see that these two conditions are often met, and to see that forecasting use has expanded steadily in the last two decades.