Societal debt collapse, also known as civilization collapse, refers to a period of national or regional economic breakdown where a fall of a complex human society takes place. Characterized by the fall or disintegration of human societies often along with their life support systems, these events can be caused by natural catastrophe, war, pestilence, and depopulation. Societal collapse broadly includes both quite abrupt societal failures typified by collapses, as well as more extended gradual declines of superpowers. Various models and theories explaining societal collapse can also be affected by environmental effects, depletion of resources, loss of creativity, rising inequality, unsustainable complexity, and decay of social cohesion as factors contributing to the decline and fall of a society.