The effects of El Nino Southern Oscillation (ENSO) on major crops, such as soybean and rice, on a global scale are presented in an article published in Nature Communications this week. Given the high reliability of seasonal ENSO forecasts, linking specific variations in global crop yields with ENSO phases has the potential to improve monitoring of food availability and famine early warning systems.
During El Nino and La Nina years, changes in the sea surface temperature of the eastern tropical Pacific Ocean lead to anomalous temperature and precipitation patterns that are known to affect regional crop yields both positively or negatively, dependent on the region. However, the impacts of ENSO on yields at global scale are yet to be concluded due to a lack of global maps assessing overall impacts of this phenomenon.
Toshichika Iizumi and colleagues present a global map of the mean impacts of ENSO on the yields of maize, soybean, rice and wheat from 1984 to 2004. Their findings show that El Nino has had a negative impact on the following: maize in south eastern USA, China, East and West Africa, Mexico and Indonesia; soybean in India and in parts of China; rice in the southern part of China, Myanmar and Tanzania and wheat in a portion of China, USA, Australia, Mexico and parts of Europe. Conversely, these events have had positive impacts on crop yields found in up to 30-36% of harvested areas worldwide, including: maize in Brazil and Argentina; soybean in the USA and Brazil; rice in parts of China and Indonesia, and wheat in Argentina and part of South Africa. Although the authors show that overall global crop yields are more affected both positively and negatively by El Nino than by La Nina, they note that La Nina has more severe negative impacts on global mean yields of rice and wheat than El Nino.
The authors suggest that the maps outlined in this work may enable national governments in import-dependent countries to manage regional trade and storage and ensure supplies of affordable food for consumers, based on the current and forecasted ENSO phase.