historyanalysisThe Conversation: Arts + Culture (US)c. 1200s · Chincha Islands, coastal Peru

How bird poo fuelled the rise of Peru’s powerful Chincha Kingdom

the gist

Seabird droppings were so valuable that the Chincha Kingdom of coastal Peru built wealth and power on them roughly 800 years ago. The islands off the Peruvian coast hold some of the largest guano deposits in the Pacific, because the dry climate stops the piles from washing away and they grow many metres tall. Guano is far richer in nitrogen and phosphorus than cow dung, so it boosted maize harvests. Chemical analysis of maize from Chincha graves shows many samples fertilised with guano, suggesting Chincha traders supplied it to farmers and merchants.

how it works

Seabirds feed on fish from the cold, nutrient-rich Humboldt current and nest on offshore islands. Their droppings build up over centuries in a dry climate where rain does not wash them away. Guano is rich in nitrogen and phosphorus, the nutrients plants need most, so spreading it on fields raises crop yields.

so what

The Chincha case shows that a fertiliser can shape political power, not just farm output. The Inca, who lacked access to marine fertiliser, seem to have valued the Chincha so highly that they restricted access to the islands and protected the birds under penalty of death.

The Conversation

Illustrative photo · en:User:Acatenazzi, CC BY-SA 3.0, via Wikimedia Commons