Like every other arena of human activity, tourism impacts the environment. We now know that tourism is not environmentally benign, as often implied by early statements on it being a preferred industry for economic development. Understanding these impacts, how they might occur, their secondary and tertiary consequences and how they might be managed is essential to good decision making about proposed tourism activity. These types of questions are important at small scales, such as construction and management of trails and campsites and at larger scales such as a tourism destination region. This chapter reviews the major subjects of environmental impacts and suggests questions appropriate for the 21st century. In an emerging world of complexity and conflict, change and uncertainty, hope and opportunity, sustainable tourism will play an important role in improving the quality of life of many of the world’s residents. Research is a significant strategy in this task, providing the data and information upon which the understanding and wisdom which serves as a gyroscope for key development decisions. Vision, of course, is not only the compass for sustainable tourism development but the key driver for science.