Human activity resulting from the Spanish conquest had a profound effect on coastal change in northwestern Peru, according to researchers at the University of Maine’s Climate Change Institute.
Daniel Belknap, a professor of Earth sciences, and Daniel Sandweiss, a professor of anthropology and Quaternary and climate studies, researched how demographic and economic effects of the Spanish conquest of the Inca Empire altered landscape development on the Chira beach-ridge plain in northern coastal Peru.
The findings were documented in an article, “Effect of the Spanish Conquest on coastal change in Northwestern Peru,” which was published the week of May 19 in the Proceedings of the National Academy of Sciences (PNAS).
The researchers determined that human activity, specifically the disposal of mollusk shells, was essential to preserving the sandy beach ridges along the Chira River in Peru.
“This type of interdisciplinary research is a hallmark of the Climate Change Institute at UMaine and contributes to better understanding of the impacts of humans on coastal systems,” Belknap says.
The study illustrates the value of comparing historic, archaeological, climatic and geological data and demonstrates that human activity alters landscapes, as well as cultures. The research also provides evidence of a previously unrecognized consequence of the Spanish conquest, according to the article.
“We show that humans had a clear effect on a coastal system that now appears to be an uninhabited, natural landscape, yet is the product of millennia of anthropogenic modification of the environment,” the report states.
The Chira River carries primarily sand at its inlet. The ridges, or narrow dunes that run for miles parallel to the shoreline, are built entirely of sand. Most ridges with sharp crests are covered by shells that are associated with fire-cracked rocks, fire pits and other artifacts that suggest the shells were deposited by humans. The shells act as armor, protecting the ridges from erosion caused by onshore winds, according to the researchers.
For more than 30 years, archaeologists and geologists have been studying beach ridges in northern Peru to better understand maritime economies, the influence of El Nino cycles and the effects of sea-level change and sediment supply on coastal systems, the article states.
Previous research has shown disposed shells are instrumental in holding sand ridges in place in the face of persistent winds. Belknap and Sandweiss, who conducted a field examination of the ridges in 1997, hypothesized that only the shell-armored ridges are stabilized and would maintain their shape and prevent winds from blowing sand inland.
The studied region was the first area in Peru to experience the direct effect of European presence, according to the researchers. In 1532, Francisco Pizarro and his conquistadors moved to the Chira Valley, where they founded the first Spanish settlement in what is now Peru.
The Spanish conquest caused extreme depopulation of the Chira coast within a century, which drastically changed the economy and devastated traditional coastal shellfish harvesting. North of the Chira River, the changes affected the evolution of beach ridges, the article states.
The researchers found the last well-preserved ridge corresponds in age with the Spanish conquest of the region, and they correlate the devastation of the coastal population after European contact with a distinctly different geomorphology.
Population growth into the 19th and 20th centuries no longer resulted in shell waste on the coastal ridges because of mollusk exportation to interior markets. For the past 500 years, demographic decline and economic change have eliminated shell heaps on the coast, causing the newly formed dune ridges to dry up and eventually blow inland.
The researchers suggest there may have been more ridges than the nine documented dunes in the Chira beach-ridge plain, but for cultural and climatic reasons, there was no shell waste to stabilize them and some of the ridges may be composites of several events.
Contact: Elyse Kahl, 207.581.3747