Between the 1840s and the 1930s, Peru and Chile exported hundreds of millions of tons of nitrogen-rich guano (dried bird excrement) and sodium nitrate (NaNO3) to places as far-flung as California, Virginia, Prussia, Great Britain, and France. For farmers in North America and Europe, guano and sodium nitrate dramatically increased agricultural productivity during the final phase of the Industrial Revolution, which lasted from roughly the mid-1800s through World War I. The widespread availability of imported fertilizers also facilitated a departure from organic “closed systems” of farming, in which nitrogen is cycled among soil, plants, animals, and people at the local scale, toward “open,” energy-intensive approaches to agriculture that included additions of nitrogen from distant places.
This major human intervention in the nitrogen cycle was closely linked to fundamental shifts in global labor relations during the Age of Abolition (1780s–1880s). In 1807, Britain outlawed the importation of African slaves to its colonial empire. The following year, the United States banned the importation of slaves, while in 1811, Spain abolished chattel slavery at home and in all of its colonies except the “sugar islands” of Cuba, Puerto Rico, and Santo Domingo. Despite such overwhelming victories for abolitionism, new forms of servitude emerged to replace those that faced extinction. Often these arrangements involved debt peonage, the repayment of loans with fixed periods of physical labor.