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El Niño events intensify food insecurity

19 October 2021

In years of extreme climate variability, nearly half the world’s children under the age of five are more at risk for malnutrition.

A field of wheat
Wheat field in Paraná, Brazil. Credit: Darlan Baluta, CC BY-SA 3.0

In the late 19th century, farmers in India suffered repeated massive crop failures, in part because of a string of severe El Niño–Southern Oscillation (ENSO) events, which dramatically lowered the rainfall there. (For more on ENSO, see the article by David Neelin and Mojib Latif, Physics Today, December 1998, page 32.) The extreme climate events, coupled with poor political decisions by the British colonial rulers, led to widespread famine. Tens of millions of people died.

The effect of ENSO on nutrition and human health continues today. Jesse Anttila-Hughes (University of San Francisco), Amir Jina (University of Chicago), and Gordon McCord (University of California, San Diego) have now published a report on child malnutrition in tropical regions. They found that when ENSO events lower precipitation, children in those regions experience weight loss and stunted growth for years after the initial climate perturbation.

ENSO variability is commonly characterized using an index that measures how far the sea surface temperature in the equatorial Pacific Ocean differs from the normal value. The researchers first compared the ENSO index with the surface temperature in various locations.

Once they had a list of countries whose local temperature significantly correlated to the index, they cross-referenced it to a standard measure of children’s health—here their weight and height—over time, based on the Demographic and Health Surveys funded by the US Agency for International Development. The comparisons yielded a data set of 1.3 million children under the age of five in 51 countries in 1986–2018. Most countries on the list are located in Latin America, South Asia, and Sub-Saharan Africa.

Statistical analyses revealed significant differences in the children’s weight, height, and body mass index during warm-phase events compared with cool-phase ones, also known as La Niña events. In warm-phase conditions, the number of underweight children relative to age increased by 0.6% per 1 °C increase in temperature. The authors argue that the effect of ENSO on agriculture links it to nutritional deficiencies in children, but they also note that other factors, such as conflict and political instability, could also affect children’s health.

During 2015–18, 34% of the children in the sampled countries were underweight. To meet the United Nations’ sustainable development goal of eliminating food insecurity by 2030, the number of underweight children would need to decrease by 2.6% per year. ENSO complicates that effort. Jina and his colleagues found that another warm-phase event equal in magnitude to the 2015 El Niño event would delay by one year the progress toward achieving the sustainable development goal. (J. K. Anttila-Hughes, A. S. Jina, G. C. McCord, Nat. Commun. 12, 5785, 2021.)

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