https://www.brynmawr.edu/news/mining-monoliths-easter-island-may-have-enriched-soil-and-helped-farming

"...the most striking feature of Easter Island (Rapa Nui) is the hundreds of enormous stone statues, known as moai, scattered around the island. Nearly all of the moai are carved from the same stone: a volcanic tuff found in Rano Raraku, one of the lower craters of the Terevaka volcano which forms the bulk of Easter Island.... it was previously assumed that the quarry existed solely as an industrial site, but the study found that starting in roughly 1400 A.D, the quarry was also a major agricultural zone. Carving the moai caused pieces of tuff to be embedded in the soil, which significantly enriched it with phosphorus, potassium, and other crucial minerals. The Rapa Nui grew sweet potato, banana, taro, paper mulberry, and bottle gourd in the quarry with significantly higher crop yields than the rest of the island, and with much lower labor needs. Whats more, the researchers posit that the Rano Raraku soil itself was a valuable and protected resource, and could very well have been transported from Rano Raraku to enrich other areas in need of increased productivity."

Full paper: https://www.sciencedirect.com/scienc...05440319300809