The Foundation of the U.S. Empire: The Role of Bird Guano

In December 1855 and January 1856, a trio of vessels set sail from the United States to Jarvis and Baker islands, coral atolls in the middle of the Pacific Ocean. The ships carried representatives from the newly formed American Guano Company and a guano expert tasked with examining the quality of the islands’ bird poop.

After estimating the quantity of guano available and taking samples, the entourage claimed the islands in the name of the company and the United States. That move marked the country’s first effort to acquire territory overseas.

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U.S. ownership of those islands became official in July 1856 with Congress’ passage of the Guano Islands Act. That act gave the country “permission” to claim sovereignty over any allegedly uninhabited or unclaimed territory to secure access to guano, a prized fertilizer for American tobacco, cotton and wheat fields.

Ostensibly the act was meant to provide the United States with a guano supply outside of Peru, home to the most coveted, nitrogen-rich guano in the world. Peru first attracted guano diggers from Britain in the early to mid-1800s, followed shortly after by the United States. At varying points, both countries considered forcibly taking Peru’s Lobos Islands, then home to 30-meter-tall guano heaps.

But the Guano Islands Act gave more than the gift of bird poop, says environmental sociologist Mauricio Betancourt of Washington and Lee University in Lexington, Va. It enabled the United States to seize some 100 far-flung islands, 10 of which remain in the country’s possession today.

When the guano craze ended decades later as supplies were exhausted, the United States converted those islands into military bases and strategic refueling stops. During the Vietnam War, the country used Johnson Atoll, a small Pacific island acquired through the Guano Islands Act in March 1858, to store and later incinerate the chemical weapon Agent Orange.

“Not enough emphasis has been placed on the ecology (and specifically on guano) as the historical basis of U.S. empire,” writes Betancourt in September in Socius.

The idea that the U.S. empire was built on bird dung reflects more than a change in historic narrative. This and other examples of ecological imperialism illuminate how land grabs to acquire resources alter the environment and occasionally advance scientific knowledge. Science News spoke to Betancourt to learn more about the neglected story of guano and its modern-day repercussions. This interview has been edited for length and clarity. 

SN: What triggered the guano frenzy?

Betancourt: The guano trade began because Europe had an important problem of soil depletion. [In the early 1800s] Britain was undergoing an agricultural revolution. It was maximizing the yield of some cash crops of wool, cereals for grazing, et cetera. That increased food production.

Justus [von] Liebig, one of the foremost German chemists … argued back then that soil fertility had to be replenished because removing the nutrients from the soil couldn’t be done indefinitely. That could provoke a problem of soil exhaustion.

Because [German naturalist Alexander von] Humboldt brought some samples of guano back to Europe in 1804 after traveling [to Peru], the Europeans were well aware of its remarkable fertilizing properties. And so they brought guano all the way from Peru to Britain around Cape Horn because the Panama Canal didn’t exist. The French and the Americans followed suit.

The guano trade also catalyzed the construction of the Panama Canal.

SN: What was so great about seabird poop from Peru?

Betancourt: [Liebig] clearly and scientifically communicated to the scientific public in Europe that nitrogen was one of the key fertilizing elements.

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The guano off Peru stands alone in terms of the nitrogen content … because of its location in a place … where it very rarely rains. So the guano retains its percentage of nitrogen and it’s not washed off or watered down by the rain. Pacific guano was not as good, actually. It’s … more humid so the guano has a higher concentration of phosphate relative to nitrogen.

SN: How did such intense guano excavation affect Peruvian ecosystems?

Betancourt: Because of what is known as upwelling, a lot of nutrients [at] the bottom of the ocean are resurfaced. This [also] happens off Namibia, the Canary Islands and California. But Peru for other reasons, [such as being] closer to the equator, has a very high concentration of nutrients. Phytoplankton attract a lot of zooplankton. There are so many birds there … because there’s a lot of fish. The guano is the culmination of the transmission of all of those nutrients from the ocean to the phytoplankton, zooplankton, fishes and birds.

Guano diggers built settlements on [Peru’s] islands. You had hundreds of people living there for 40 years. That scared the birds. There are no precise estimates of the size of the populations back then. Probably there were about 50 million birds. Today, there are a few hundred thousand birds.

SN: Once Peru’s guano supply was exhausted, nations turned to another nitrogen source: Chilean nitrates. What was the impact?

Betancourt: The nitrates were of geological origin [found in desert salts], but it’s the same story [of ecological imperialism]. Chile’s nitrates were also exhausted eventually. And this prompted the War of the Pacific from 1879 to 1883, between Chile backed by Britain versus Bolivia and Peru. Bolivia and Peru lost the war and they had to cede part of their territories in perpetuity to Chile.

SN: How did the world satisfy its appetite for nitrate-based fertilizers after that?

Betancourt: Fritz Haber, a German chemist, discovered a chemical reaction in the early 1900s … whereby he could use molecular nitrogen gas from the atmosphere [and] combine it with hydrogen in a very energy intensive chemical reaction to produce ammonia. Basically, he discovered the way to synthesize synthetic fertilizer from nitrogen in the air, which is, to this day, the process whereby most synthetic fertilizer in the world is produced.

Many people claim that that reaction was what allowed the population explosion from 1 billion to 6 billion in the 20th century. [Haber] was even was awarded the Nobel Prize for chemistry in 1918 for developing this reaction, partly stemming from what guano taught the world.

SN: Is mined guano still a sought-after commodity?

Betancourt: It’s interesting because it’s pretty much for domestic consumption [in Peru]. But it’s also exported in a sense. [Farmers] apply it to coffee. The nutrients end up accumulating in the coffee. And that coffee gets exported to Europe and to the U.S.