Assessing the Impact of ENSO on South American Agriculture

The 2011/12 South American summer growing season was characterized by a severe drought that significantly reduced agricultural production. This was particularly true for Argentina, Brazil, and Paraguay, which are important producers and exporters of commodities such as soybeans and corn. The culprit was the cold phase (La Niña) of the El Niño / Southern Oscillation (ENSO) phenomenon, which has been documented to cause periods of unseasonable warmth and dryness in these countries during the southern hemisphere summer. Long-lead forecasts depicting anomalously low sea surface temperatures in the equatorial Pacific correctly anticipated the development of the La Niña, which was to be the second in as many seasons; consequently, weather forecasters and crop analysts anticipated potential problems well before the start of the South American summer planting season. As the event unfolded, however, it became obvious that the 2011/12 event would differ significantly from the 2010/11 La Niña, underscoring the difficulties faced by analysts attempting to develop crop forecasts using correlative measures.

Using information obtained from the Climate Prediction Center (NOAA/NWS/CPC), weather and crop analysts from the United States Department of Agriculture (USDA) attempted to define the possible impacts of the La Niña at the onset of the growing season. The products, which offered a unique perspective on the cyclical, albeit sometimes-erratic, nature of ENSO, were used in briefings to top USDA staff in an effort to educate non-meteorologists on the benefits, and limitations, of using products of these type operationally. When combined with historical weather and climate information, CPC data and products supported a vast array of assessments that successfully anticipated several key impacts of the drought on agriculture.

This paper outlines the methodologies employed by USDA's World Agricultural Outlook Board in identifying and assessing the impacts of drought on South American agriculture. In particular, specific ENSO-related products that proved to be the most useful will be identified, and suggestions will be offered for consideration of future products, which could prove useful in identifying climate-based drought risk worldwide. The unprecedented fluctuations in prices observed since late 2011 due to locally severe droughts in both North and South America reinforce the importance of assessing the usefulness, and potential economic value, of these types of products and analyses.