There are islands off the coast of Peru that owe their color to bird guano. I saw some of them this past weekend, after a thirty minute boat ride from the small coastal town Paracas, south of Lima. Once we made it out to the Islas Ballestas, our boat guide pointed out the species – Inca Terns, Guanay Cormorants, Humbolt Penguins – and told us that in five years’ time, workers would scrape 60-70 centimeters of guano off the rocks to sell as fertilizer. The islands smelled like old, sour fish.

There were two workers who lived on the islands, both guano harvesters. Our boat cruised by the old wooden docks that, a hundred and fifty years ago, were surely much busier. At that time, our guide told us, there would be five to six meters guano for workers to mine, annually. In mid-19th century Peru, no commodity was more important than bird guano.

The droppings were mined and exported as phosphorus- and nitrogen-rich fertilizer around the world. Peru’s guano was especially sought-after because the country’s climate (little rain, arid atmosphere) better preserves the nitrates from evaporating. From 1840 to 1880 (Peru’s Guano Golden Age), the country exported 20 million tons of guano, earning around US$2 billion in profits.

Chinese coolies began arriving to toil here after slavery was abolished here in 1854. The coolies in the guano mines and sugar plantations were nearly all men and all bound to eight years’ servitude if and when they made it through their passage from Macau to Lima.

In the New World, the coolies endured conditions on par with the slaves that had preceded them: squalor and neglect, prolonged bouts of illness, back-breaking work and physical punishment. At night, they were thrown together with the army deserters and convicts they worked alongside in cramped rooms and locked up until morning.

Guano harvesting in the 19th century was similar to how it is done today. From an enlightening New York Times article published last year:

Guano is also an undeniably strenuous enterprise from the perspective of the laborers who migrate to the islands to collect the dung each year. In scenes reminiscent of open-pit gold mines on the mainland, the laborers rise before dawn to scrape the hardened guano with shovels and small pickaxes.

Many go barefoot, their feet and lower legs coated with guano by the time their shifts end in the early afternoon. Some wear handkerchiefs over their mouths and nostrils to avoid breathing in guano dust, which, fortunately, is almost odorless aside from a faint smell of ammonia.

Meanwhile, the worldwide “guano rush” was on. The British Empire monopolized Peru’s guano trade in places like the Islas Ballestas. The US Congress, in turn, passed the Guano Islands Act in 1856. This allowed any American citizen to take peaceable possession of any “deposit of guano on any island, rock or key” not inhabited or occupied by another government. All told, the US would claim around 60 islands in the Caribbean and Pacific on guano grounds.

As artificial fertilizers were developed later in the 19th century, guano’s importance plummeted. Peru’s economy suffered a steep decline, acerbated by its foreign debt and years of mismanaging its guano income.

Fast-forward a hundred and fifty years, and now, Peru’s guano is back in demand. From the Times article mentioned above, guano from Peru is fetching up to US$500 per ton as an organic alternative to synthetic fertilizers. While the article isn’t positive about guano’s long-term viability – one interviewee predicts supplies will last another 10 years before bird populations are completely gone – it is a fascinating read.

I came away more (cautiously) optimistic after my guano run-in, however. Granted the islands I visited were in a national park, but there seemed no shortage of birds or guano. The droppings were sensibly being harvested every five years, and we tourists didn’t even step foot outside the boat. If nothing else, these small, barren rocks aren’t really usable for anything besides what falls on them. What would the government have to lose by protecting a few more guano islands from fisherman and trampling tourists, and making a few bucks in the process?