Living as humans necessarily means we will have some impact on the environment around us. But as human populations grow and our affluence and technological capabilities increase, we collectively consume more and more natural resources. The concept of ‘Ecological Footprint’ is one of the most recognised environmental indicators to measure this growing human consumption. Since the early 1970s, human resource demand has exceeded the planet's ability to renew natural resources. In the interests of continued human well-being and survival, the Ecological Footprint provides a clear warning that our current consumption trajectory cannot be maintained in the long term. The Ecological Footprint – new developments in policy and practice by Andrea Collins and Andrew Flynn is a story about why the Ecological Footprint (EF) has been such a successful environmental indicator. Not only can the EF communicate complex concepts very clearly (the finiteness of resources, the equitable distribution of resources and the link between local and global resource consumption), it also has resonance for a wide range of people – from policymakers, the public, NGOs, academics, the media and politicians alike. What makes this book stand apart is its analysis of how effective the EF concept has been for changing practices and policy. The analysis is built on the authors’ rich personal experience of policy implementation and learnings from key players all over the world. The lessons presented in the book show that environmental indicators do not inform a rational, linear decision-making process – no matter how accurate or reliable the indicator is nor how powerful and clear their message. The reality of policymaking is that it is messy: there are conflicting interests and perspectives at play; policymaking is influenced by power relationships; and implementation is context sensitive and inherently political. Indeed, choosing an environmental indicator in the first place is influenced by this same complex reality. It is the authors’ detailed experience of the EF policy development process in the Welsh Cardiff Council which exemplifies this fascinating policy reality. Here, an inclusive process was used that involved policymakers, NGOs and university staff. Many expert-led processes may result in the marginalisation of environmental indicators before policy change can be achieved. The detailed case study (together with comparisons from elsewhere) shows the importance of building relationships and trust between different stakeholders through joint deliberation and participatory decision-making that is sensitive to local context. The authors highlight the importance of preparatory work and collective knowledge building. What this book further reveals is the importance of the human side of the EF, not just the numbers. The authors’ analysis of governance is critical. In their own case study in Wales, they demonstrate, for instance, the importance of collaborations between ‘experts’ and decision-makers, including decision-makers at multiple levels and including decision-makers across portfolios (especially beyond the environmental portfolio). All this is critical for negotiating the complexity associated with policy change. They also identify cases when the Ecological Footprint did not lead to policy change and why. There is a lot to learn here for anyone wanting to increase their effectiveness as a practitioner of sustainability, whether it is using the EF or not. While the EF continues to be measured, its influence on decision-making remains uncertain. In this book, Collins and Flynn documented much of the past experiences with the Ecological Footprint concept around the world and describe the lessons from these experiences. They make a valuable contribution to our understanding of policy and practice that is both thought provoking and fascinating. This is a wonderful book for anyone who would like to move past ‘knowing more’ to ‘changing more’ – be they policymakers or community practitioners.