El Niño Southern Oscillation (ENSO) is a weather pattern spawned by warming in the Pacific Ocean’s surface temperature as warm water currents head east from Australia toward South America. Undersea volcanic activity in the Pacific may contribute to this warming. A high-pressure zone in the western Pacific accompanies this warming. Eighteenth-century Peruvian sailors noticed this phenomenon occurring regularly in December, and they thus named it “El Niño”—the boy—in reference to the baby Jesus. Rising surface water temperatures due to global warming likely augment modern ENSO cycles. ENSO’s effects, like drought or flooding, however, are variable and only somewhat predictable because local weather events also influence them. Davis suggests that ENSO played a significant role in the drought-famines of the late 19th century yet cautions against holding weather solely responsible for these disasters. The British, for instance, made the effects of the ENSO-fueled droughts in India worse because they failed to regulate grain prices, did not effectively fund famine relief, and exported grain to England instead of supplying it to drought-stricken regions.

Political ecology is the social scientific approach Davis uses to study the relationship between humanity and the environment. This approach suggests that political, social, and economic impacts on the environment are significant, and their study cannot be separated.