Guano is the excrement of seabirds, cave-dwelling bats, pinnipeds, or birds in general. As a
manure, guano is a highly effective fertilizer due to its exceptionally high content of nitrogen,
phosphate, and potassium, three nutrients essential for plant growth. The nineteenth-century
guano trade played a pivotal role in the development of modern input-intensive farming practices
and inspired the formal human colonization of remote bird islands in many parts of the
world. During the twentieth century, guano-producing birds became an important target of conservation
programs and influenced the development of environmental consciousness. Today, guano
is increasingly sought after by organic farmers.
Composition Seabird guano consists of nitrogen-rich ammonium
oxalate and urate, phosphates, as well as some earth salts and impurities. Unleached
guano from favored locales, such as the Chincha Islands off the coast of Peru, typically contains
8 to 16 percent nitrogen, 8 to 12 percent equivalent phosphoric acid, and 2 to 3 percent
equivalent potash. The fresh excrement of insect-eating bats can have nitrogen levels
approximating that of seabird guano and high phosphate levels, but bat guano typically
has less fertilizing value than seabird guano from arid areas because its nitrogen content
is more easily leached within cave environments. History
The word "guano" originates from the Andean indigenous language Quechua, which in its
original usage refers to any form of dung used as an agricultural fertilizer. Archaeological
evidence suggests that Andean people have collected guano from small islands and points
located off the desert coast of Peru for use as a soil amendment for well over 1,500 years.
Spanish colonial documents suggest that the rulers of the Inca Empire assigned great value
to guano, restricted access to it, and punished any disturbance of the birds with death. The
Guanay cormorant has historically been the most abundant and important producer of guano.
Other important guano producing species off the coast of Peru are the Peruvian pelican
and the Peruvian booby. In November 1802, Alexander von Humboldt was
the first European to encounter guano and began investigating its fertilizing properties
at Callao in Peru, and his subsequent writings on this topic made the subject well known
in Europe. During the guano boom of the nineteenth century, the vast majority of seabird guano
was harvested from Peruvian guano islands, but large quantities were also exported from
the Caribbean, atolls in the Central Pacific, and islands off the coast of Namibia, Oman,
Patagonia, and Baja California. At that time, massive deposits of guano existed on some
islands, in some cases more than 50 m deep. In this context the United States passed the
Guano Islands Act in 1856, which gave U.S. citizens discovering a source of guano on
an unclaimed island exclusive rights to the deposits. Nine of these islands are still
officially U.S. territories. Control over guano played a central role in the Chincha
Islands War between Spain and a Peruvian-Chilean alliance. Indentured workers from China played
an important role in guano harvest. The first group of 79 Chinese workers arrived in Peru
in 1849, by the time that trade ended a quarter of a century later, over 100,000 of their
fellow countrymen had been imported. There is no documentary evidence that enslaved Pacific
Islanders participated in guano mining. After 1870, the use of Peruvian guano as a
fertilizer was eclipsed by saltpeter in the form of caliche extraction from the interior
of the Atacama Desert, not far from the guano areas. During the War of the Pacific Chile
seized much of the guano as well as Peru's nitrate-producing area, enabling its national
treasury to grow by 900% between 1879 and 1902 thanks to taxes coming from the newly
acquired lands. Contrary to popular belief, seabird guano does not have high concentrations
of nitrates, and was never important to the production of explosives; bat and cave-bird
deposits have been processed to produce gunpowder, however. High-grade rock phosphate deposits
on Nauru, Banaba Island, Christmas Island, and other raised atolls were not produced
by marine birds. Since 1909, when the Peruvian government took
over guano extraction for use by Peru farmers, the industry has relied on production by living
populations of marine birds. U.S. ornithologists Robert Cushman Murphy and William Vogt promoted
the Peruvian industry internationally as a supreme example of wildlife conservation,
while also drawing attention to its vulnerability to the El Niño phenomenon. South Africa independently
developed its own guano industry based on sustained-yield production from marine birds
during this period, as well. Both industries eventually collapsed due to pressure from
overfishing. The importance of guano deposits to agriculture elsewhere in the world faded
after 1909 when Fritz Haber developed the Haber-Bosch process of industrial nitrogen
fixation, which today generates the ammonia-based fertilizer responsible for sustaining an estimated
one-third of the Earth's population. DNA testing has suggested that new potato
varieties imported alongside Peruvian seabird guano in 1842 brought a virulent strain of
potato blight that began the Irish Potato Famine.
Sourcing
The ideal type of guano is found in exceptionally dry climates, as rainwater volatilizes and
leaches nitrogen-containing ammonia from guano. In order to support large colonies of marine
birds and the fish they feed on, these islands must be adjacent to regions of intense marine
upwelling, such as those along the eastern boundaries of the Pacific and South Atlantic
Oceans. Post-depositional decomposition and ammonia
volatilization of penguin guano also plays an important role in the evolution of ornithogenic
sediments in the cold and arid environment of Antarctica.
Bat guano is usually mined in caves and this mining is associated with a corresponding
loss of troglobytic biota and diminishing of biodiversity. Guano deposits support a
great variety of cave-adapted invertebrates, that rely on bat feces as their sole source
of nutrition. In addition to the biological component, deep guano deposits of both kinds
contain local paleoclimatic records in strata that have built up over thousands of years,
which are unrecoverable once disturbed. The greatest damage caused by mining to caves
with extant guano deposits is to the bat colonies themselves. Bats are highly vulnerable to
regular disturbance to their roosts. Some species, such as Phyllonycteris aphylla, have
low fat reserves, and will starve to death when regularly disturbed and put into a panic
state during their resting period. Many species will drop pups when in panic, with subsequent
death, leading to a steady reduction in population. Research in Jamaica has shown that mining
for bat guano is directly related to the loss of bat species, associated invertebrates and
fungi, and is the greatest threat to bat caves on the island. However, when done with caution,
extraction of guano can be done alongside marine bird colonies without causing them
significant harm. Properties
In agriculture and gardening guano has a number of uses, including as: soil builder, lawn
treatments, fungicide, nematicide, and as composting activator.
In popular culture In Joseph Conrad's 1900 novel Lord Jim the
characters Chester and Captain Robinson attempt to recruit the eponymous lead character for
an expedition harvesting guano. The setting of Ian Fleming's 1958 installation
in the James Bond series Dr. No is a Caribbean guano island, and the villain dies at the
end buried in guano. In Stanley Kubrick's 1964 film Dr. Strangelove,
Colonel "Bat" Guano leads an attack on the airbase responsible for sending a nuclear
attack order to bomb the Soviet Union. In the 1995 film Ace Ventura: When Nature
Calls, Jim Carrey's character attempts to save an African tribe from being dispossessed
of a fortune in bat guano. See also
Histoplasmosis Phosphorite
Uricotelic organisms History:
Bat Cave mine Guano Era, Peru
Guano Islands Act References
Further reading Cushman, Gregory T. Guano and the opening
of the Pacific world: a global ecological history. Cambridge; New York: Cambridge University
Press. ISBN 9781107314030. Retrieved 2013-06-13. Hague, James D. On the phosphatic guano islands
of the Pacific Ocean. Retrieved 2013-06-13. Skaggs, Jimmy M. The great guano rush: entrepreneurs
and American overseas expansion. New York: St. Martin's Press. ISBN 0312103166.
Robinson, Solon. Guano: a treatise of practical information for farmers.
New York: Solon Robinson. Retrieved 2013-06-13. Pacific Guano Company. The Pacific Guano Company;
its history; its products and trade; its relation to agriculture. Exhausted guano islands of
the Pacific Ocean; Howland's island, Chiacha Islands, etc., etc. The Swan Islands. The
marl beds and phosphate rock of South Carolina. Chisolm's Island phosphate. The menhaden.
Cambridge: Printed for the Pacific Guano Company at the Riverside Press. Retrieved 2013-06-13.
Teschemacher, James E.. Essay on guano; describing its properties and the best methods of its
application in agriculture and horticulture; with the value of importations from different
localities; founded on actual analyses, and on personal experiments upon numerous kinds
of trees, vegetables, flowers, and insects, in this climate. Boston: A.D. Phelps. Retrieved
2013-06-13. Africa
Teale, E.O.. The Limestone caves and hot springs
of the Songwe river area with the notes associated Guano deposits XII. The East Africa Natural
History Society. Retrieved 2013-06-13. Chile
Pissis, Aimé. Nitrate and Guano Deposits in the Desert of Atacama: An Account of the
Measures Taken by the Government of Chile to Facilitate the Development Thereof. London:
Taylor and Francis. Retrieved 2013-06-13. Peru
Duffield, Alexander James. Peru in the guano age: being a short account of a recent visit
to the guano deposits, with some reflections on the money that they have produced and the
uses to which it has been applied. London: Richard Bentley and Son. Retrieved 2013-06-13.
Duffield, Alexander James. The Prospects of Peru: The End of the Guano Age and a Description
Thereof. With Some Account of the Guano Deposits and Nitrate Plains. London: Newman & Co. Retrieved
2013-06-13. Hollett, Davi. More Precious than Gold: The
Story of the Peruvian Guano Trade. Fairleigh Dickinson. ISBN 1611473578.
Nesbit, John Colis. On agricultural chemistry, and the nature and properties of Peruvian
guano. London: Longman and Co. Retrieved 2013-06-13. Documents
"Prospectus of the American Guano Company". 1855. Retrieved 2013-06-13.
Coker, Robert Ervin. The fisheries and the guano industry of Peru. Washington DC: Government
Printing Office. Retrieved 2013-06-13.
United States Department of Agriculture, Office of Experiments. Bat guanos of Porto Rico and
their fertilizing value. Mayagüez, P.R.: Porto Rico Agricultural Experiment Station.
Retrieved 2013-06-13. External links
ProAbonos Jamaican Bat Guano and Cave Preservation
The dictionary definition of guano at Wiktionary