How did bird droppings become the 19th century's white gold?

Guano became valuable because several things coincided. Peruvian islands held enormous deposits of seabird droppings rich in nitrogen and phosphate. Farmers in Europe and North America faced exhausted soils and growing populations. Chemists then explained why the material worked, and governments and merchants built a trade around it. Peru's state captured much of the profit. According to Encyclopedia.com, roughly 11.5 million tons were shipped over four decades, worth about $750 million in total. [1] [2]

Guanay cormorants, Peruvian boobies and pelicans nested for millennia on rocky islands off South America's arid Pacific coast. With almost no rain to wash the droppings away, they built up in towering layers. Encyclopedia.com credits the conditions of the Humboldt Current, and says the deposits were sometimes hundreds of feet thick on the Chincha Islands. Indigenous farmers on Peru's coast had used the material since at least the 13th century, according to The Conversation, while Spanish colonists used it only sparingly. [3] [1]

Alexander von Humboldt brought guano samples to Europe in the early 1800s. In 1805 the chemists Fourcroy and Vauquelin published an analysis showing their nitrogen content. European commercial interest only began around 1840, possibly prompted by Justus Liebig's work on chemistry and agriculture, according to the Science History Institute. The Conversation says Liebig and other chemists showed that crops depend on replacing the nutrients removed from the soil. [4] [3]

The timing mattered. Atlas Obscura describes European and American farmers worrying about depleted soil, and The Conversation notes that growing cities drew food from distant farms but returned few nutrients. Guano contained nitrogen, phosphate and potassium together, which set it apart from alternatives such as sawdust or ground cow horn. Liebig himself acknowledged its value but stressed self-sufficiency through recycling human and animal waste. [2] [3] [4]

Peru declared a national monopoly over guano in 1841. It sold through consignment deals, dominated early on by the British firm Antony Gibbs and Sons, and later through contracts with Peruvian merchants and the Dreyfus Contract of 1869. Encyclopedia.com says the state captured about 60 percent of final sales, and that extraction relied on convicts, coolies and other poorly treated laborers. BirdLife's DataZone, using a slightly different figure, puts exports from 1840 to 1870 at about 12 million tons, and records that the Guanay Cormorant was toasted as the most valuable bird in the world. [1] [5]

The United States entered through the Pacific. Smithsonian Magazine reports that ships returning from the Gold Rush sought cargo, and the Guano Islands Act let the president use the Navy to protect claims to islands. Historian Cushman says guano was a prestige commodity among Southern cotton planters, a sign of a modern, scientific farmer. [6]