Tourism is a large, diffuse global industry. Environmental aspects are little studied, with ~1,500 publications in total. Impacts range from global contributions to climate change and ocean pollution to localized effects on endangered plant and animal species in protected areas. Environmental management is limited more by lack of adoption than by lack of technology. Government regulation is more effective than industry based ecocertification. In developing nations, tourism can contribute to conservation by providing political and financial support for public protected area agencies and for conservation on private and communally owned lands. This is important in building resilience to climate change. In developed nations, such effects are outweighed by the impacts of recreational use and by political pressures from tourism property developers. These interactions deserve research in both natural and social sciences. Research priorities include more sophisticated recreation ecology as well as legal and social frameworks for conservation tourism.