Mutualistic and symbiotic interactions are foundational concepts in the field of ecology and occur frequently in nature. Such interactions are often so important that they are necessary for the survival, reproduction and evolution of life. This article discusses various mutualistic and even parasitic interactions between different life forms and the cactus genus Copiapoa, endemic to the Atacama Fog Desert of northern Chile. The authors' fieldwork and observations reveal that Copiapoa are keystone plants in their habitats, with their flowers, fruits, seeds, cortical tissues, and even necrotic tissues being the base of the food chain for many endemic Chilean insects that often have mutualistic relationships with these cacti. It is therefore critically important that Copiapoa habitats are preserved for the future. Aside from the obvious threat of climate change and drought in northern Chile, other conservation issues such as habitat destruction and illegal extraction of Copiapoa still need to be addressed.