Economic cutbacks are being blamed for a ‘guano alarm’ in the Italian capital of Rome, where millions of migrating starlings have left their droppings in great quantities across the city. In addition to its distasteful odour and sight, the guano presence is believed to pose a threat to Winter tourism if not treated.
The problem has arisen due to the cancellation of anti-starling measures as a result of Italy’s economic woes. These include loudspeakers broadcasting the calls of birds of prey and the pruning of plane trees to encourage the birds to move on swiftly. Slipping pedestrians and cyclists are becoming a daily event and the incident is being touted as a national embarrassment.
Some parts of the world, however, would kill for an influx of guano on this scale. Unsavoury as it may be, guano is an effective fertiliser when produced in large quantities, and helped revolutionise global agriculture in the 19th century.
Prior to the 1840s, the premier way of improving soil quality was by adding bone meal (crushed up bones) either of animals or, more disturbingly, humans to the earth. This dubious methodology persisted until the Europeans discovered the merits of guano, particularly that of sea birds.
The largest deposits of guano in the 19th century were on the ‘bird islands’ off the Pacific coast of South America, territories uninhabited by humans. These guano deposits could accumulate to 50m in height such was the rate of build-up and lack of disturbance.
With a nitrogen content in the region of 15%, guano had the potential to rapidly accelerate plant growth and improve crop yields. The Peruvian Incas and their predecessors had practiced guano fertilisation for centuries before the arrival of Europeans who, blinded by the pursuit of gold and silver in the 16th century, ignored a potentially lucrative trade.
It was not until the great naturalist Alexander von Humboldt sent a sample of guano to a colleague in France, having witnessed its use in agriculture during his ventures in South America (1799-1804), that its potency was discovered. This set in motion the fascinating guano trade.
Islands off the coast of Peru, especially the Chincas, were set-upon by enterprising entrepreneurs. Sensing an opportunity, the Peruvians nationalised the Chinchas and imported thousands of Chinese labourers for their workforce. Subjected to living on excrement-covered islands, which gave off a toxic smog when dug, the Chinese suffered terribly for the benefit of the developed world.
By the mid-19th century, Britain alone was importing almost 220,000 tons of guano and processing works were established in London. This included the Anglo-Continental Guano Works and the De Pass Guano Works in Barking, which not only utilised guano for fertiliser but also in the manufacture of explosives.
Guano extraction works were established off Brazil, the Caribbean and the US during the 19th century, with Chinese labourers and African slaves making up the bulk of the workforce. Treated appallingly, many died. This did not deter the Americans whose government passed the Guano Islands Act in 1856 which gave American citizens the right to claim islands that held guano deposits, a classic case of economic imperialism.
Such was the impact of guano fertiliser that demand quickly outstripped supply in Europe and prices rose. As a compromise, sulphur was imported from Italy to act as a substitute in guano processing. The Guano Islands Act, meanwhile, started to be manipulated by merchants keen to seize the assets of other nations. Spanish seizures of Peruvian and Chilean guano islands, meanwhile, led to the Chincha Islands War (1864-1866).
It was not until the early 20th century that the advent of artificial fertilisers put a fatal halt on the guano trade but its importance in agricultural and sociological development cannot be underestimated. As Charles C Mann notes:
Industrial monoculture with improved crops and high-intensity fertilizer allowed billions of people – Europe first and then much of the rest of the world – to escape the Malthusian trap.
It is worth bearing this in mind each time we complain about the bird mess on our car windscreens or on the pavement at our feet.
Source: Mann Charles C, 1493: Uncovering the New World Columbus Created
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