The rubber boom that brought death and destruction to many Amazonian peoples did not have such a serious effect on the Achuar because of their bellicose nature and their geographic isolation. As the boom ended, however, more and more fortune seekers moved into Achuar territory. This also coincided with the increase in demand for resin from the leche caspi tree (Couma macrocarpa), which is found in abundance around the Pastaza River.During the 1940s and 1950s, many traders and merchants settled in Achuar territory and learned the language, establishing commercial relationships based on debt labor, providing the Achuar people with tools, weapons and clothes on credit, in exchange for leche caspi.