Risks of Extreme Heat and Unpredictability

摘要

In their report "historical warnings of future food insecurity with unprecedented seasonal heat" (9 January, p. 240), D. S. Battisti and R. L. Naylor argue that because agricultural yields are severely reduced in anomalously hot years, a general rise in average growing season temperature over this century will threaten food security. The authors identify a crucial issue but, by focusing on historic extremes, they frame it incorrectly. Extreme events are rare and result in lower yields primarily because farmers do not plan for them and crop breeders do not breed for them. If the currently extreme temperaturesrnbecome the norm, then we would expect farmers to adapt, maintaining yields by selecting alternative crop varieties, species, and cultivation techniques. Examining the performance of agriculture under unprecedented conditions tells us little about how it will adapt to future climates.