Hidden away among the endless strata of mineral specimens at the Museum of Natural History in Berlin is a corked glass jar of caked tan powder with scattered flecks of grey (Figure 1). Its main label identifies it simply as ‘Guano, excrement of birds, that was found in great abundance along the coast of Peru’. The specimen has long since lost its once-pungent scent of wet dog and has been kept in the museum’s teaching collection for decades. How did a sample of Peruvian bird dung find its way into one of Europe’s most prestigious mineralogical collections? The answer is not hard to fathom: Guano played a critical role in the economic and geopolitical transformation of the modern world, from Lima to London and Berlin.

From the 1840s into the 1950s, a handful of capitalists and states made vast fortunes from this malodorous commodity, exploiting a labour trade that recruited tens of thousands of Chinese, Pacific Islander, Andean and Afro-Peruvian labourers to perform the dirty work of excavating entire mountains of dried excrement. During the ‘guano boom’ of 1840–80, revenues from the trade provided a fabulous but volatile source of income for the Republic of Peru. Meanwhile, the transnational race to acquire guano islands and two closely related commodities, nitrates and phosphates, inspired vast empire-building campaigns. These devolved into three major wars: the Chincha Islands War (1864–6), the War of the Pacific (1879–84) and, in guano’s last phase, the Second World War.

Guano’s farthest reaching impact on modern history has been ecological. During the four decades of its initial boom, guano exports from the coast of Peru, and smaller quantities mined from southern Africa, the equatorial Pacific and other bird islands, increased by a factor of ten the amount of concentrated nitrogen, phosphate and potassium available on the world market for farming and industry (Figure 2). Guano was the Miracle-Gro of the mid 19th century. It was expensive, but it enabled profit-minded northern farmers to save the cost of fallowing their land or paying workers to shovel farmyard manure by the wagonload. By a similar logic, farmers preferentially applied it to fodder crops with the goal of maximising high-value animal and meat production. During the 20th century, guano was redirected to sugar and cotton plantations in Peru and to wheat fields in South Africa whose crops were intended for export. Rather than providing bread to the hungry masses of the industrial age, guano enabled the prosperous to eat ever higher on the food chain.

Guano by itself did not establish the ‘metabolic rift’ favouring the productivity and prosperity of the industrialised global North over the colonised global South. Indeed, Peruvians’ re-appropriation of guano for their own use during the 20th century – based on the careful conservation of living colonies of marine birds – calls into question such grand North–South dichotomies and narratives. Nevertheless, guano was fundamental to the popularisation of new, input-intensive agricultural practices worldwide that have made farms ever more reliant on ecological productivity from distant environments. This, in turn, encouraged the development of new extractive industries aimed at multiplying the world’s nitrogen, phosphate and potassium supplies. In the process, this massive mobilisation of nutrients by industrial agriculture not only enabled the multiplication of members of our own species but also fundamentally altered the chemistry and ecology of soils, aquatic ecosystems and the atmosphere all over the world. Guano, therefore, deserves a prominent place in any museum or cabinet of curiosities of the Anthropocene, our current ‘human epoch’ of planetary history.

Humboldt did not discover guano or its uses. Its history runs deep in Peru. Guano-producing birds and guano-rich islands appear prominently in ancient ceramics of the Moche culture of coastal Peru, and the chemical signature of guano has been identified in pottery from the Nazca valley that is more than two thousand years old. Hundreds of artefacts have been found buried deep within Peru’s guano deposits, including an early colonial coat of arms belonging to Don Pedro Guañeque, a native lord. Guano received prominent attention in the best-known early modern scholarly writings on Peru. For the Jesuit naturalist José de Acosta, long resident in Peru, guano was an icon of natural theology. ‘For in addition to being ugly in themselves’, he wrote, the seabirds that produce guano ‘are good for nothing except to void excrement; yet even so, they may be no less useful.’ The erudite padre continued, ‘I have thought about this and been astonished by the providence of the Creator, who has decreed in so many ways that the other creatures must serve man … So not only the flesh of birds to eat, and their songs to delight us, but their very excrement serves to improve the earth.’¹ For the Peruvian mestizo historian Inca Garcilaso de la Vega, guano was a paragon of the good government of the Inca kings from whom he was directly descended. ‘In the time of the Inca kings’, he wrote,

these birds were so carefully watched that no one was permitted to land on the islands during the breeding season under pain of death, so that they should not be disturbed or driven from their nests. It was also illegal to kill them at any season either on the islands or elsewhere, under pain of the same penalty. Each island was assigned, on the Inca’s instructions, to a certain province, or if it was a large island, to two or three provinces … Each village had its piece and each householder in the village his part, according to the quantity of manure he was reckoned to need … and the taking of any in excess of it was punished as an infringement of the law. Nowadays the manure is used quite differently.²

For the enlightened Spanish explorers Jorge Juan and Antonio de Ulloa, guano was a wondrous curiosity of natural history and an exemplar of the natural abundance of the Viceroyalty of Peru. Ulloa made a special trip out to ‘these islands when several bark-lined vessels came to load with it; at which time the insupportable smell left me no room to doubt of the nature of their cargo’.³ All these commentators agreed that this natural fertiliser was extraordinarily effective, existed in prodigious quantities, supported a vibrant coastal trade and was derived in one way or another from the vast, insular colonies of marine birds that dotted the arid Peruvian coast.

Guano’s transmutation from a well-known Peruvian resource into an international scientific obsession occurred largely thanks to the intervention of the ambitious Prussian naturalist Alexander von Humboldt (1769–1859). But farmers of the global North did not automatically adopt Peruvian guano as a fertiliser after its collection and certification by European chemical science. This required the advocacy of scientists and entrepreneurs from Peru, most notably the Arequipa-born savant Mariano Eduardo de Rivero y Ustáriz (1798–1857), as well as field experiments carried out by a far-flung international network of local agricultural societies.

Although the episode is routinely omitted from histories of Humboldt’s explorations, he had very important business to attend to on the coast of Peru. He timed his arrival to Lima to correspond with the passage of Mercury across the face of the sun on 9 November 1802. After stationing his instruments atop the tower of the great fortress of Callao, Peru’s most important port, Humboldt calculated the record altitude that he and his companions claimed to have reached during their failed ascent of Mount Chimborazo. He also investigated the ancient native use of balsa wood in coastal shipping, and passed the time sketching a fur seal and penguin (Figure 3). But one phenomenon impressed itself on Humboldt’s senses more powerfully than any other during his time on the Pacific Coast. While prowling the docks of Callao, he could not help but notice several barges filled with a substance known among locals by the Quechua word wanu. It smelled so powerfully of ammonia that Humboldt erupted in fits of sneezing when he got too close. He had first seen large piles of this manure north of Lima ready to be laid on coastal agricultural fields. Locals assured him that barges travelled frequently to the Chincha Islands to the south to mine deposits estimated to be at least 15 metres thick. He doubted local opinion that the cormorants and flamingos he had seen on his way down the coast could produce such massive quantities. But it began to dawn on him that guano might have been the vital ingredient that had allowed Peru’s native population to reach into the millions before the arrival of the Spanish, and that had enabled the Chimú civilisation to build the massive network of aqueducts and earthworks that he had visited near Trujillo along the northern Peruvian coast.

Humboldt returned to France in August 1804 after five years in the New World. It took him another three decades under the courtly patronage of the Prussian king and 30 volumes, most in French, to write up the results for a primarily European readership. But Humboldt wasted no time in arranging for Europe’s foremost chemists to analyse the samples of guano he had brought back with him from Callao. He did so not only because he recognised the uniqueness of guano but because sharing such specimens was a critical means of cultivating his network of relationships with other scientists – that is, of cementing his reputation as an important source and agent of scientific discoveries. On 26 November 1804, Antoine François de Fourcroy and Louis Nicolas Vauquelin presented a detailed quantitative analysis of guano before the pre-eminent academic institution of Napoleonic France, the Institut National des Sciences, Lettres et Arts. Their analysis was accompanied by a report by Humboldt crediting Peru’s native peoples with guano’s discovery. He also speculated that Peru’s guano reserves had formed slowly over aeons of geological time, like the coal deposits of Britain. Martin Heinrich Klaproth, Prussia’s leading analytical chemist and a former mentor to Humboldt, also analysed a sample and published his results in his widely read mineralogy handbook. In a series of four experiments, Klaproth determined that his sample was 16 per cent uric acid (a substance rich in nitrogen that is prevalent in bird and reptile faeces and kidney stones), 10 per cent phosphate of lime, and 28 per cent quartz sand, among other substances. Klaproth also published an extended report from Humboldt, the manuscript original of which can be found among the pages of Humboldt’s Peruvian diary. The mineral collections of Klaproth and Humboldt formed the initial core of what became the mineralogical cabinet of the Berlin Museum of Natural History after it was established in 1810. In consideration of this fact, the orthography of the underscored word ‘Huano’ on the museum’s specimen label, its clear similarity with the handwriting in Humboldt’s original guano treatise and the way he consistently formed the letter ‘H’ in his signature, we can confidently conclude that the pictured museum sample once belonged to Humboldt and likely originated in Peru in 1802. These and subsequent chemical analyses showed Peruvian guano to have an exceptionally high percentage of nitrogen and phosphate for a naturally occurring substance, along with significant quantities of potassium, making it a powerful fertiliser.

English chemist Humphry Davy also gained access to a sample of guano in 1805. Davy had achieved international fame for his experiments with nitrous oxide and other chemicals. He was so impressed by Peruvian guano that it helped him decide to give up on his dream of running away to the Lake District to take up the life of a Romantic poet with his close friends Samuel Taylor Coleridge and William Wordsworth, both of whom died young because of their propensity to seek inspiration from consuming laughing gas and other mind-bending chemicals. Instead, Davy rededicated his chemical talents towards the practical study of agricultural manures, ‘for the purpose of awakening [man’s] industry, and of calling forth his powers’. Davy did more than any other figure to popularise experimentation with nitrogenous manures among science-minded farmers in the early 19th century. Another English experimenter, Alexander Beatson performed the first highly publicised field experiments with guano outside Peru, using locally collected guano on the tropical island of St Helena. Beatson had just been appointed governor and wanted to prove that this degraded South Atlantic island could be converted into a valuable plantation colony with the help of modern science.

A transhemispheric war prevented anyone from capitalising on these discoveries for many years. Peru had witnessed massive native insurrections just prior to Humboldt’s brief visit and soon became embroiled in a series of revolutionary wars that spanned the Atlantic, from Napoleon’s invasion of Iberia and the crowning of his brother Joseph Bonaparte in 1808 as king of Spain to the final surrender of the Spanish fortress at Callao to independence forces led by Simón Bolívar in January 1826. A young Peruvian disciple of Humboldt and political ally of Bolívar, Mariano de Rivero (Figure 4), played a crucial role in reviving international interest in guano. His father had attended the famous Cortes of Cadiz as a representative of southern Peru. Rivero’s father had denounced unsustainable harvesting of Peruvian guano at the Cortes in 1812, making a controversial request to have the Arequipa region released from the centralised control of Lima, the capital of the Viceroyalty of Peru. His son became a close confidant of Humboldt during the late 1810s while studying to become a mining engineer in Paris, far from his war-torn homeland. Humboldt arranged for Rivero to make a tour of the Freiberg Mining Academy and silver mines in Saxony, where Humboldt had received his main scientific training, in part from Klaproth. Rivero is often credited with bringing the vast nitrate deposits of the Atacama Desert to the attention of European scientists at this time, by making a sample available for crystallographic analysis by the French mineralogist René-Just Haüy.

In 1822, on Humboldt’s recommendation, Rivero was selected to staff an expedition to South America to rebuild the scientific institutions of the new federation of Gran Colombia after the devastation of the independence wars, where he served as founding director of the National Museum and School of Mines in Bogotá. After the surrender of Callao, Bolívar convinced the patriarch of Peru’s enlightened scientific community, José Hipólito Unanue, to stay on as the top civilian official of the Republic of Peru, and Unanue and his colleagues appointed Rivero to serve as director general of mines and public education. In this post, Rivero founded independent Peru’s first national museum, its first scientific journal and a mining academy in the highland city of Huánuco and published the first of several studies on Peruvian antiquities. Rivero also used his influential position to study and promote Peru’s guano industry in ways Humboldt could scarcely imagine. In 1826, Rivero made a survey of several guano islands and performed a chemical analysis that definitively proved that old guano deposits were little different from fresh guano. He also collected data on the extent of the coastal guano trade and the material’s uses by Peruvian farmers. In turn, Humboldt dutifully arranged to have one of Rivero’s articles on guano published abroad in German, French and English. Others sent a series of small consignments of Peruvian guano and nitrates to experimental farmers in England and the United States for practical tests. Then in 1840–41, an old business ally of Rivero, Francisco Quirós, orchestrated a deal to export the first large shipment of Peruvian guano to Liverpool.

To be sure, the Peruvian guano boom might never have happened if not for the growing world network of local agricultural societies. Many had taken to heart Davy’s dictum to treat the soil as a laboratory. Guano sales agents provided experimental consignments to these societies, who in turn published enthusiastic testimonials in the agricultural press as far afield as Canada, the West Indies and Mauritius. Another scientific disciple of Humboldt, Justus von Liebig, is often credited with sparking the ‘great guano rush’, not unlike the way Fritz Haber and Carl Bosch are almost singularly credited with inventing today’s industrial process for synthesising nitrogen chemicals. Liebig’s famous textbook Organic Chemistry in Its Application to Agriculture and Physiology (1st ed., 1840) enthusiastically advocated the use of mineral fertilisers by farmers but actually downplayed the value of nitrogen-rich fertilisers like Peruvian guano.

In the history of knowledge as it is broadly understood and taught in the West today, heroic northern figures like Humboldt, Liebig, Haber and Bosch have received the lion’s share of credit for many key scientific discoveries. But the Peruvian mineralogist Mariano de Rivero was even more critical than his Prussian mentor in finally delivering Peru’s native understanding of the use of bird excrement as fertiliser to the modern world. Also vital were experimental farmers – what we would now call citizen scientists – working in places as remote as the island of St Helena. After all, they were the ones who confirmed guano’s efficacy for a host of crops and environmental conditions, and who then followed up these discoveries with much larger purchases. Ultimately, however, it was the knowledge and labours of the native peoples of Peru that made the gift of guano available to the industrialising world.

FURTHER READING

Acosta, J. (2002) Natural and Moral History of the Indies [1589] (Durham, NC: Duke University Press).

Cushman, G.T. (2013) Guano and the Opening of the Pacific World: A Global Ecological History (Cambridge/New York, NY: Cambridge University Press).

Damaschun, F., and R.T. Schmitt (eds.) (2019) Alexander von Humboldt: Minerale und Gesteine im Museum für Naturkunde Berlin (Göttingen: Wallstein Verlag).

Davy, H. (1839) Elements of Agricultural Chemistry: In a Course of Lectures for the Board of Agriculture Delivered between 1802 and 1812, 6th ed. (London: Longmans).

Juan, J., and A. Ulloa (1758) A Voyage to South America [1748] (London: L. Davis and C. Reymers).

Kubler, G. (1948) ‘Towards absolute time: guano archaeology’, in A Reappraisal of Peruvian Archaeology, edited by W.C. Bennett (Menasha, WI: Society for American Archaeology and Institute of Andean Research).

Mitman, G., M. Armiero, and R. Emmett (eds.) (2018) Future Remains: A Cabinet of Curiosities for the Anthropocene (Chicago, IL: University of Chicago Press).

Möllers, N., C. Schwägerl, and H. Trischler (eds.) (2015) Welcome to the Anthropocene: The Earth in Our Hands (Munich: Deutsches Museum).

Rivero y Ustáriz, M.E. (1857) Colección de memorias científicas, agrícolas é industriales publicadas en distintas épocas (Brussels: H. Goemaere).

Rosenthal, G. (2012) ‘Life and labor in a seabird colony: Hawaiian guano workers, 1857–70’, Environmental History, 17 (4): 744–82.

Skaggs, J.M. (1994) The Great Guano Rush: Entrepreneurs and American Overseas Expansion (New York, NY: St Martin’s Press).

de la Vega, G. [El Inca] (1966) Royal Commentaries of the Incas and General History of Peru [1616–17] (Austin, TX: University of Texas Press).

¹ J. Acosta, Natural and Moral History of the Indies, ed. Jane E. Mangan, trans. Frances López-Morillas (1589; Durham, NC: Duke University Press, 2002), 238–39.

² I. Garcilaso de la Vega, Royal Commentaries of the Incas and General History of Peru, H.V. Livermore, trans. (Austin: University of Texas Press, 1966), vol. 1, 246–7.

³ J. Juan and A. Ulloa, A Voyage to South America, (London: L. Davis and C. Reymers, 1758), vol. 2, 100–1, 106–7.