From modest beginnings in the 1960s, environmental economics has grown to be a major subdiscipline of economics. It combines traditional work in the field of welfare economics and the theory of economic growth with more recent perspectives on the political economy of choosing policy instruments and the philosophy of sustainable development. The central tenets are that environmental problems have their roots in the failure of economic systems to maximize human well-being, that environmental quality matters for human well-being and for more traditionally oriented economic growth objectives, and that efficient policy can be achieved through incentive design.