Cities are the most likely actors to design and bring about lasting sustainability. An agreement among the world’s larger cities is possible, and likely a necessary but insufficient condition to achieve sustainable development. Cities and Sustainability explores the ways in which cities are both the biggest threat to sustainability, and the most powerful tool to get us to sustainable development. Employing an innovative methodology to a complex issue, the book proposes new metrics and approaches that assume cities as fundamental in the search for sustainability. Providing population projections for the world’s larger cities and a hierarchy of sustainable cities, the author develops two new tools: (i) a cities approach to physical and socio-economic boundaries, and (ii) sustainability costs curves. These tools are designed to be implemented in a multi-stakeholder, integrated partnership that truly maximizes the benefits of cities in the quest for sustainability. Applying the tools outlined in the book to case studies from Dakar, Mumbai, Sao Paulo, Shanghai and Toronto, this volume will be of great relevance to students, scholars and practitioners with an interest in urban and city management, climate change, and environment and sustainability more broadly.