A new El Niño event is emerging in Peru's climate outlook. According to the latest report from the Multisectoral Commission in Charge of the National Study of El Niño Phenomenon (ENFEN), a weak El Niño is expected.
The expert noted that these walls, strategically built at the foot of large ravines, reach imposing dimensions.
"We have found evidence that these walls were up to 33 meters long and are perfectly preserved, although they may originally have exceeded 50 meters, standing five meters high and five meters wide. They are made of large stones—some measuring more than one meter—bound together with mud and clay-rich sediments," she underlined.
Defense against extreme rainfall caused by El Niño phenomenon
Ana Cecilia Mauricio said the location and characteristics of these structures led the research team to propose the hypothesis that they were retaining walls designed to halt landslides, triggered by intense rainfall associated exclusively with El Niño events, whether coastal or global.
This hypothesis was confirmed through excavations, sediment analysis, high-resolution topographic surveys, digital terrain models, and radiocarbon dating.
The results show that the walls retained sediments coming from the ravines and, to this day, continue to protect the site's architecture.
"These structures not only functioned in the past but continue to fulfill their purpose thousands of years later," the archaeologist emphasized.
Climate, innovation, and adaptation
The researcher highlighted that the dating of the walls coincides with paleoclimatic studies indicating an increase in the frequency and intensity of El Niño events around 4,000 years ago — a key period in the climatic history of Peru's coastline.
"This climatic phenomenon spurred technological innovation. Populations understood their environment, studied the site's geology, and developed solutions to mitigate the impacts of rainfall," Mauricio indicated.
The communities that inhabited Salinas de Chao belonged to the preceramic period, a stage prior to the use of pottery and the formation of states or empires.
They were communal organizations that, with limited resources and without complex technology, managed to build effective protection systems using local materials such as stone and mud.
A lesson that remains relevant for present-day Peru
According to the researcher, the finding leaves a clear message: El Niño does not have to inevitably translate into disaster.
"Today, every El Niño event finds us underprepared. Bridges, schools, homes, and farmland get destroyed. By contrast, ancient populations not only protected themselves but even knew how to harness the rains to make the desert productive," Mauricio underlined.
In addition to the retaining walls, she reported evidence of excess-water channeling, the use of sediments to create farmland, and the expansion of agricultural areas in valleys such as Chao and Chicama.
Replicable ancestral infrastructure
Ana Cecilia Mauricio noted that this type of solution can be adapted to the present day, especially in low-resource communities, which are often the most affected by extreme climate events.
"It is not about literally copying these structures, but about understanding the principle: studying the environment, knowing the risks, and designing local solutions with accessible materials," she emphasized.
A legacy repeated throughout history
While Salinas de Chao represents the oldest known evidence, later records point to similar infrastructure during the Moche and Chimu periods, as well as at sites such as Manchan, demonstrating a continuity of ancestral knowledge in addressing climate-related risks.
"Ancient Peru had a different way of relating to El Niño. That accumulated experience is knowledge we should recover and apply," she concluded.