Sustainability and unsustainability are frequently deployed in discussions of intended, predicted and observed changes occurring in or impacting on Pacific islands societies. Local communities often have their own distinctive understanding of the natural environment. Their concern for sustainability frequently extends further afield - to languages, cultures, and other aspects of life. International agreements and the constitutions of a number of Pacific islands countries address relevant issues. Constitutional government in the region has been remarkably sustained. Sustainable development has diverse dimensions and can be controversial. Climate change and rising sea-levels threaten the very survival of low-lying islands. Harvesting of non-renewable resources raises particular issues. Pacific islands studies have made significant contributions to scientific knowledge and human understanding of issues and processes of wider, even global importance.