Designed by a partnership of UN agencies, international scientific organizations, and development agencies, the Millennium Ecosystem Assessment (MA) is the most extensive study ever of the linkages between the world's ecosystems and human well-being. The goal of the MA is to establish the scientific basis for actions needed to enhance the contribution of ecosystems to human well-being without undermining their long-term productivity. With contributions by more than 500 scientists from 70 countries, the MA has proven to be one of the most important conservation initiatives ever undertaken, and the ecosystem services paradigm on which it is based provides the standard for practice. This manual supplies the specific tools that practitioners of the paradigm need in order to extend their work into the future. The manual is a stand-alone "how to" guide to conducting assessments of the impacts on humans of ecosystem changes. In addition, assessment practitioners who are looking for guidance on particular aspects of the assessment process will find individual chapters of this manual to be useful in advancing their understanding of best practices in ecosystem assessment. The manual builds on the experiences and lessons learned from the Millennium Ecosystem Assessment global and sub-global assessment initiatives, with chapters written by well-known participants in those initiatives. It also includes insights and experiences gained from a wider range of ecosystem service-focused assessment activities since the completion of the MA in 2005.