A key area of public policy in the last twenty years is the question of how, and how much, to protect the environment. At the heart of this has been the heated debate over the nature of the relationship between economic growth and environmental sustainability. Is environmental sustainability economic growth or `green growth’, a contradiction in terms? In his research, Prof Paul Ekins has broken new ground in defining the conditions of compatibility between economic growth and environmental sustainability, and provided measures and criteria by which the environmental sustainability of economic growth, as it occurs in the real world, may be judged. He has argued that `green growth’ is not only theoretically possible but economically achievable and has shown what environmental and economic policies are required to achieve this.