Jared Diamond’s argument about the society of Easter Island is laid out in Chapter 2 of this book. Diamond argues that the people of Easter Island essentially abused their environment. They did things to the environment that were not sustainable. Eventually, they managed to degrade their environment so badly that they were not able to sustain a large population with a decent standard of living.
By the time that Europeans got to Easter Island, about 800 years after it was settled by Polynesians, the island had no trees. It had very few sources of food. It also had a small population living in poor conditions. Diamond says that all of this happened because the people of Easter Island had depleted their resources through overuse.
Diamond uses scientific evidence to establish that Easter Island once had a lot of trees. The trees were used to make canoes, to make tools, to burn in fires (many of them were used to cremate corpses), and presumably to make things to help move the huge stone statues that the islanders made. The trees were also cut down to allow for more agriculture.
Diamond argues that the cutting down of the trees destroyed the island’s environment and economy. It made it impossible for them to make canoes to use for fishing or porpoise-hunting in the open ocean. It made it impossible for them to make ropes to pull their statues. It ruined the quality of the soil and reduced food yields. It helped to destroy populations of wild food species.
All in all, Diamond argues that the people of Easter Island overused their environment to the point where their civilization collapsed.