All the environmental issues covered in this book are, by definition, made up of physical and human elements. The approach throughout is to analyse both the physical problems and the human responses to understand why the issues are issues, and how solutions can be found. Although particular issues are apparent at particular spatial scales, all have some manifestation on the global scale. In the case of climatic change brought about by atmospheric pollution, the issue affects the entire planet because climate is a global phenomenon. In other cases, more localized issues have become so commonplace that, cumulatively, they occur on a worldwide scale. Environmental problems associated with agriculture, urban areas, industrial pollution, waste management, warfare, deforestation and soil erosion are just a few examples of such cumulative global issues. Since so many environmental issues now have a global nature, many believe that the time has come for a complete rethink of the way we view these issues, for a change in the philosophy that lies behind the ways in which people interact with the environment, and for a change in the methodology with which the interactions occur. The approach most widely advocated by this rethink is sustainable development, and this chapter looks in more detail at the need for sustainable development and some of the ways in which it might work.