Located approximately 21 kilometers off the southern coast of Peru, the Chincha Islands are home to extensive deposits of seabird guano that have accumulated over centuries. This nitrogen-rich substance became a highly sought-after fertilizer in the 19th century, significantly influencing global agricultural practices and trade.
Recent archaeological studies reveal that the use of this vital resource dates back much further than previously believed. A research paper published on February 11 in PLOS One provides compelling evidence that ancient communities in Peru's Chincha Valley started using seabird guano to fertilize maize as early as 1250 C.E., well before the area became part of the Inca Empire.
Thriving in Harsh Conditions
The Chincha Valley presents a challenging and arid environment. Between 1000 and 1400 C.E., the Chincha Kingdom flourished despite these harsh conditions. How did they manage to cultivate crops in such a landscape? While archaeologists recognized their wealth as traders, the secret to their agricultural success may lie in their use of a specific type of fertilizer.
Along the Peruvian coast, seabird guano is abundant, and its application could have been crucial for the Chincha farmers. Emily Milton, a co-author from the Smithsonian's National Museum of Natural History, noted that effective soil management, facilitated by this fertilizer, would have been essential for supporting population growth. This suggests that the ability to enhance soil fertility was key to the kingdom's prosperity.
However, researchers faced a challenge: they did not find direct evidence of ancient fertilizer usage. Instead, they utilized chemical analysis to uncover the truth. Led by Jacob Bongers from the University of Sydney, the research team examined 35 maize cobs found in ancient burial sites. By analyzing stable isotopes of nitrogen, carbon, and sulfur, they were able to infer the growing conditions of these plants.
The findings were remarkable, with many samples displaying exceptionally high nitrogen levels, indicating the presence of seabird guano. This chemical signature aligns with the artwork of the Chincha culture, which frequently depicts seabirds, fish, and growing plants, illustrating the connection between the ocean and their diet.
This evidence collectively indicates that Chincha farmers successfully integrated marine resources into their agriculture, ensuring a stable food supply for their thriving coastal society.
A Resource from the Sea
Harvesting guano was no simple task; it required advanced seafaring skills and organized labor. The Chincha had to navigate coastal waters, collect the guano, and transport it back to their valley. This level of organization likely set the stage for the Inca Empire, which later implemented strict regulations to protect seabird populations and manage guano access.
Jo Osborn, another co-author from Texas A&M, emphasized that the true strength of the Chincha lay not just in their access to resources but in their understanding of a complex ecological system. They possessed the knowledge to bridge the gap between marine and terrestrial ecosystems, ultimately transforming that knowledge into an agricultural surplus that supported their civilization.
Interestingly, while scientists often analyze chemical isotopes in bones to reconstruct ancient diets, crops fertilized with marine-derived guano can yield chemical profiles similar to seafood. As Milton pointed out, the introduction of seabird guano into crops creates a "false marine signal" in terrestrial food products.
This study suggests that the organized use of fertilizer in the Chincha Valley began well before the Inca era, providing a clearer understanding of early agricultural practices in coastal Peru.