http://video.nationalgeographic.com/video/player/places/parks-and-nature-places/cave-canyon-desert/us_grandcanyon.html
Its the elephant in the room that is not often mentioned. Grand Canyon National Park gets millions of visitors a year, arriving in gasoline or diesel powered vehicles, staying in large hotels and lodges along the Canyon rim, and enjoying the full range of comforts from home. There is an environmental impact of potentially loving the area to death. National Geographic briefly examines
This video struck me in part because AZGS is currently a cooperating agency with the BLM's EIS process to look at the potential environmental impacts of uranium breccia pipe exploration and mining in northern Arizona. I don't know how the tourism impacts would stand up to the same rigorous scrutiny.