This short paper explores the question: what is environmental degradation and what are its causes? It seems an obvious question, but it is not. The paper explores definitions of environmental degradation (and restoration), challenging simplistic perspectives centred on ‘carrying capacity’. Five explanations of the root causes of environmental degradation widely applied in policy debates and promoted by different actors are identified. These are: (1) (neo-)Malthusian arguments about scarcity and environmental crisis; (2) technological and ecomodernist explanations; (3) perspectives on resource inequality, distribution, and development; (4) views that centre on human–nature caring relationships; and, finally, (5) arguments for more fundamental structural change and transforming capitalism. Each suggests a very different interpretation of causes and effects with contrasting implications for research design, policy, and practice. The paper is aimed at providing a quick overview of the debates, helping to inform discussions about environmental restoration and protection. Too often such debates do not explore underlying causes. While biophysical dynamics are important, environmental degradation – and so restoration – must take account of social, political, and cultural dimensions of environmental change.