Guano's origin

The use of guano as fertilizer in agriculture is very ancient. The word guano comes from Quechua, (Inca’s language), means “excrement of marine birds.” Even before the Incas, Peruvian coastal cultures had discovered their usefulness for agriculture. However, it will not be until the nineteenth century when it begins to be used massively, becoming a subject of great economic and strategic value. 

Guano is the accumulation of the seabirds’ dejections. These birds inhabit the islands and capes of the Peruvian coast. Among the most representative birds, are the Guanay (Phalacrocórax bouganinvilli Lesson), the Piquero (Sulavariegata Tshudi) and the Pelican (Pelecanus thagus). These birds feed themselves with hydrobiological species.  The manure accumulation of 5 to 6 years makes guano the best natural organic fertilizer in the world.    In the nineteenth century, Guano was used massively, becoming a subject of great economic and strategic value, it was a commodity that trigger invasions and wars at the time.

Guano in Europe

In 1802, the naturalist Alexander von Humboldt collected guano samples and sent it to France for analysis.  Around 1840, European farmers began importing guano as they saw how their crops improved, which led the United States to become interested in this product, generating a significant market. Its location was basically reduced to several Peruvian and Caribbean islands and to a few places on the African coast, although the quality of guano from Peru led the country to produce it almost monopolistically. It was not long before businessmen emerged who exploited the natural deposits of guano in a massive way, using workers mostly from China and Japan.

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More about Guano: The Great Peruvian Guano Bonanza: Rise, Fall and Legacy

Mineralization (transformation)

Due to the entry of cold water from the Humboldt stream from the south, the climate in the Peruvian Coast, presents moderate temperatures and scarcity of rainfall.  That is the reason why the guano nutrients are preserved in the islands. In these conditions the seabird’s droppings accumulate in several years and through biochemical oxidation, the microbial activity  transforms complex substances into a series of nutrients.  


  • Guano is a natural fertilizer, biodegradable & ecological.
  • Guano completes the process of      mineralization of the soil, transforming in humus and minerals, releasing      nutrients through a microbiological process.
  • Guano improves the physical-chemical and microbiological conditions of the soil.
  • Guano favors the absorption and      retention of water.
  • Guano contributes with microbial  flora and organic matter. 
  • Guano is soluble in water and      easily assimilated by plants (mineralized fraction).
  • Guano’s properties work in synergism.

The Guano Era (1800-1880)

During the 1800s the world was aware of the guano as the fertilizer with high nitrogen content, that is when intense exploitation of the ancient deposits of guano began. By the late 1800s, guano deposits stored for centuries had been almost exhausted. Nevertheless, many demanded protection of the seabirds and their islands. In 1905, climate changes by the El Niño stream caused birds to leave their nests, making Guano, the most prized fertilizer in the world.   The Peruvian Guano Administration (1909-1965) began working in 1909 with a great success achieved in handling the conservation of three seabird’s species.  Also, the management and conservation of seabirds and revival of production were in the hands of hired professionals such as: Robert E. Coker, American Marine Biologist (1875-1967), Henry Ogg Forbes, Scottish Naturalist (1851- 1932), Jose Antonio de Lavalle y García, Peruvian Agronomist (1888-1957), William Vogt, American Ornithologists (1902-1968), and Enrique Avila (1917-1972) and Romulo Jordan (1929.2007), both Peruvian Ornithologists. (Cushman 2005). Great management and conservation of few species was achieved, although the situation of other species was affected.  Even though, the experience gained, today’s concerns regarding management measures of seabirds and guano are the same as that of a little over a century ago (Zavalaga 2015) just because the management always faces new challenges to overcome.  The pioneer in pursuing the management and conservation of seabirds and guano production was the marine biologist Robert E. Coker (1875-1967).  The topic of guano has been extensively reviewed by Gregory T. Cushman. (Irma Franke).

The Coker Mission 1906-1908

Peruvian elites in the early 1900’s concentrated their efforts on agriculture and mining for export, and benefited from the incredible wealth of Peruvian coastal waters, one of the most productive marine ecosystems in the world. The American ornithologist Robert Cushman Murphy, gave a lively testimony in this regard. He observed as he sailed off the Peruvian Coasts in the 1910’s, “vast and boiling banks of shallow fish, whales emerging, incredible flocks of birds _herds of frolicking sea lions _ Groups of turtles, much larger than anyone I have seen through hundreds of degrees of latitude in the Atlantic" (Murphy 1925).  The Peruvian government sought a US conservation technocrat for advise. In June 1906, the Ministry of Development allocated resources to hire a marine biologist to do a research in Peruvian waters.   The US Fisheries Division, world leader in oceanography, recommended, Robert E. Coker (1875-1967), Coker was a young professional scientist trained in United States marine biology according to the German research model. He had a recent Ph.D. in zoology from J. Hopkins University 

Coker arrived in Peru, in November 1906. He systematically explored the ports, islands and peninsulas of the Peruvian coast in a sailboat to studied all sea species.  So, he could propose appropriate regulations for fishing, guano extraction and sea lion hunting.   He also advised on the improvement of shellfish farms near the border with Ecuador. Between May and July of 1907 spent a total of 25 days observing the bird colonies and activities of the guano workers in the islands Chincha and Ballestas and managed to negotiate the extension of his contract until February of 1908 to observe the guano islands during the peak of the breeding season. His itinerary gave Coker the opportunity to make comparative observations on almost the entire coast of Peru, although he did not have the opportunity to conduct long-term investigations.

The most valuable birds in the world

The richness of the Peruvian marine environment caused great admiration in Coker: “Perhaps there are no other waters in the world more abundant provided with small fish than those of Peru.” He was also impressed by the effectiveness of local fishing methods and the willingness of fishermen to adopt new practices.   

Coker reserved his strongest recommendations for the Peruvian guano islands. He thought that the depletion of the last remaining deposits of guano was imminent and, after watching the workers of the private corporation destroy a colony of 80,000 pelicans in the “Lobos de Afuera” island, he feared the entire industry to extinction.  But, thanks to a law banning the entrance of people to the islands decreed by the government, seabirds had a quiet home in its natural environment. The challenge that the government encountered is to determine the exploitation system that could preserve deposits of guano in a long term for national agriculture and for exporting.   Cooker proposed a system of monopoly concessions for each island that would eliminate fierce competition between private interests. To keep each island in a state of peace, Coker proposed a system that rotated the guano crop between the islands – the longer the period of closure, the better. Coker shared the conviction of José Otero, that a government enterprise was the one most likely to succeed. Coker argued that harvesting the guano in this way, based on sustained yield, could achieve gains much higher than its cost.