Biodiversity and ecosystem services provide tangible benefits for society, such as food provisioning, water purification, genetic resources or climate regulation. These services provide critical life support functions and contribute to human health, well being and economic growth. Yet biodiversity is declining worldwide and, in some areas, this loss is accelerating. The need for policies that promote the conservation and sustainable use of biodiversity and ecosystem services is more important than ever. Payments for Ecosystem Services (PES) is a direct and flexible incentive-based mechanism under which the user or beneficiary of an ecosystem service makes a direct payment to an individual or community whose land use decisions have an impact on the ecosystem service provision. Interest in PES has been increasing rapidly over the past decade: PES are proliferating worldwide and there are already more than 300 programmes in place today at national, regional and local levels. Drawing on the literature concerning effective PES and on more than 30 case studies from both developed and developing countries, this book aims to identify good practice in the design and implementation of PES programmes so as to enhance their environmental and cost effectiveness. It addresses the following questions: Why are PES useful and how do they work? How can they be made most effective environmentally and how can their cost-effectiveness be maximised? What are the different potential sources of finance for PES programmes, and how can they be secured? and What are the lessons learned from existing PES programmes and insights for future programmes, including international PES?