An advertisement for guano to be used as fertilizer depicts not only seabirds but also a guano island.

(AMHERST, MASS.) The closure of the Strait of Hormuz, through which roughly one-third of the world’s fertilizer normally passes, has made clear that access to nutrients for crops remains as strategically important in the 21st century as access to oil.

As an environmental historian, I study how fertilizer transformed the modern world. That history is about more than scientific innovation or agricultural progress. It also reveals the hidden costs of modern food production, including the brutal treatment of workers and the expansion of imperial power.

Originally published on theconversation.com, part of the BLOX Digital Content Exchange.

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