The two pictures in this post seem to have nothing to do with each other, but they are connected by a surprising history: “white gold,” aka guano, i.e. bird excrement. This stuff once drove human cultures in these now depopulated areas.
The first image shows the Atacama Desert of Chile, the driest non-polar desert in the world. It is a region so devoid of rainfall that it has been used as an experimentation site for potential expeditions to the planet Mars, and its skies are so absent of clouds that the area is one of the very best places in the world for astronomical observations. Yet in a paper published in the journal _Nature Plants_ in January 2021, a team of scientists showed that plant and human remains dating after 1000 CE show such high levels of nitrogen isotopes that they conclude guano was used to intensify agriculture in this desert.
Guano contains “fixed” nitrogen, a form of this element essential for plant life. From the beginning of farming until the commercial fertilizers of the early 20th-century, a dearth of nitrogen (as well as phosphorus and potassium) was a constant problem for the human food supply.
And this explains how indigenous Chileans were able to use guano to sustain human habitation in an otherwise hostile environment so many centuries ago.
Fast forward to the mid-19th century, when the white gold became a majorly sought-after commodity by Europeans and Americans. The guano boom from the 1840s-1870s had far-ranging effects. The second image shows Chinese laborers who were virtually enslaved and forced to mine guano on Peru’s Chincha islands. Peru had become the world’s largest guano exporter. With some islands having about 200 feet of the stuff, it made the Peruvian government very wealthy.
Until it didn’t, because people mined the guano resources past sustainability. The communities of birds were threatened, and Europeans and the U.S. government had to look elsewhere to find their main source of fertilizer.
Sources: “‘White gold’ guano fertilizer drove agricultural intensification in the Atacama Desert from 1000 AD” _Nature Plants_ 25 Jan 2021, Francisca Santa-Sagredo et al, pp 152-158. _Atlas Obscura_ “When the Western world ran on guano,” Cara Giaimo, Oct 14, 2015. _Natiinal Museum of American History_ “The guano trade,” images from shudderstock and American Museum of Natural History/WikiCommons Public Domain.
