Book excerpt: The fourth report in the Global Environment Outlook series provides a comprehensive, scientifically credible, policy-relevant and up-to-date assessment of, and outlook for, the state of the global environment. Environment for development is the GEO-4 underlying theme and the report pays special attention to the role and impact of the environment on human well-being as well as to the use of environmental valuation as a tool for decision-making. GEO-4's 2007 publication date marks the half-way point for the Millennium Development Goals, The environment, as well as being the subject of MDG 7, is also a thread that runs through all the goals. Includes Errata.