This work analyzes the changes (both positive and negative) that have occurred in the environment in the past two decades. It focuses not only on the state of the environment but also on the interactions between development activities and the environment. It highlights the main responses since 1972 to protect the environment, and is based on a review of the scientific literature, UNEP reports, and other sources. First the report describes the state of the world environment and summarizes environmental problems. It then highlights the environmental impacts of development activities and describes the impacts of both the state of the environment and development activities on human conditions and well-being. Then follows a review of the perceptions, attitudes and responses of people towads environmental problems. The book concludes with a section outlining future challenges and priorities for action to protect the environment and conserve natural resources.