What caused the wars on Easter Island that led to the demise of this once-thriving civilisation? People and places - Physical geography - Islands Learning Points If an island can provide all its own resources, it is self-sufficient. A self-sufficient island must use its resources responsibly to maintain a sustainable environment. A Twig Context Film. Reinforce and extend the learning required by the curriculum. Twig’s context films show abstract concepts in action in the real world.