The second edition of the OECD Environmental Outlook is based on projections of economic and environmental trends to 2030, and even to 2050 in some key areas. It looks at the best policies to tackle the challenges we face today, including climate change, biodiversity loss, toxic chemicals, and water scarcity. The focus has been expanded from the 2001 edition to reflect developments in OECD countries and Brazil, Russia, India, and China, as well as the interactions among them. OECD Environmental Outlook to 2030 addresses the following questions: how will economic and social developments drive environmental change to 2030? What policies are needed to address the main environmental challenges? How can OECD and non-OECD countries best work together to tackle these challenges? The key findings are summarized using traffic lights to highlight “red light” issues that need to be addressed urgently. There are also “yellow light” issues that require further investigation or some action and “green light” issues for which countries should proceed with caution.