This paper reviews the past ten years of research on the environmental impacts of tourism. It identifies that a major problem in tourism and environment research has been the lack of experiments that take base-line measurements prior to development and then track environmental change over time. The majority of work has been reactionary and conducted after the damage has taken place, with no comparative data available to document the extent of change or damage. It is also not possible to estimate how much impact is directly tourism related, as opposed to natural change or impacts from factors other than tourism. Research that begins before development occurs, takes base line measurements, and tracks environmental change over an extended period, is critical to understanding tourism's impacts on the environment