Widely studied question, from diverse focuses. Perphaps better to search for that issue directly, for instance, in http://www.opendoar.org/search.php, in order to select focus. Annexed one resource from my own (that touch that topic).
Article Rural tourism and urban sprawl in inland areas. Socio-spatia...
Pickering, C. M., & Hill, W. (2007). Impacts of recreation and tourism on plant biodiversity and vegetation in protected areas in Australia. Journal of Environmental Management, 85(4), 791-800.
Bushell, R., & Eagles, P. F. (Eds.). (2007). Tourism and protected areas: benefits beyond boundaries: the Vth IUCN World Parks Congress. CABI.
West, P., Igoe, J., & Brockington, D. (2006). Parks and peoples: the social impact of protected areas. Annu. Rev. Anthropol., 35, 251-277.
Nepal, S. K. (2000). Tourism in protected areas: the Nepalese Himalaya.Annals of Tourism Research, 27(3), 661-681.
Marion, J. L., & Reid, S. E. (2007). Minimising visitor impacts to protected areas: The efficacy of low impact education programmes. Journal of Sustainable Tourism, 15(1), 5-27.
West, P., & Brockington, D. (2006). An anthropological perspective on some unexpected consequences of protected areas. Conservation Biology, 20(3), 609-616.
Newsome, D., & Moore, S. A. (2012). Natural area tourism: Ecology, impacts and management (Vol. 58). Channel View Publications.
“Wildlife Watching and Tourism” (2006) a report on the potential for wildlife watching tourism to contribute to community development and conservation; and on practical ways to use planning and visitor management to ensure the long-term sustainability of this activity, published by the UN Convention on Migratory Species