While ecotourism and sustainable travel operators are minimizing the damage inflicted on World Heritage Sites, the sheer volume of travelers and irresponsibility on the part of tourists, urban planners and multinational corporations could see some of the world’s most famous wonders being closed to the public.

The latest biannual watch list compiled by the World Monuments Fund (WMF), a New York-based preservation group, places over 93 sites in 47 countries at risk from urban development, tourism, neglect and bad planning. Though comprised mainly of ancient structures, the 2010 Watch List also includes 15 sites built in the 20th century. According to Agence France-Presse, WMF president Bonnie Burnham described the sites on the list as “places that define and enrich our lives and environment and without which our world wouldn’t be the same.” Sites listed include the Incan ruins of Machu Picchu in Peru; the traditional wooden houses in Kyoto, Japan; and the thatched royal tombs of Uganda.

Local communities near some popular destinations are becoming aware of the dangers of too much tourism. In August, Easter Island residents staged a major protest against the influx of tourists by pitching tents and moving trucks onto the airport runway. Though the island’s economy relies on tourism revenues, overcrowding is becoming a problem. Easter Island’s population of 4,900 is 29 percent higher than in 2002, and islanders concerned about the environment are calling for controls on commerce.

In the Galápagos Islands, the Ecuadorian government has instituted a policy to control tourist numbers. Residents of Easter Island would like to see similar restrictions adopted there. “We ask, for example, that those who arrive have a card which describes the activity they will be doing here, just like in the Galápagos Islands,” the island’s mayor, Luz Zasso, told The Guardian.

Meanwhile, the Pitcairn Islands, in the Pacific, have succeeded in establishing immigration controls for “short-period” and “long-period” tourists, while in glitzy Venice, proposals to pre-book tours and cap the number of visits to the city have met with resistance from the more democratically minded.

Although local authorities typically place the blame for tourism-related problems largely on the behavior of travelers, the WMF says poor management of tourism-related enterprises and high-rise buildings that destroy the character of ancient cities are just as much to blame for their decline.

In a nutshell, says Xavier Font of Leeds Metropolitan University’s Centre for Responsible Tourism, a balance needs to be struck to ensure that tourism-generated funds, which often benefit large foreign companies rather than local economies, save famous sights rather than erase them. “There is a cycle of damage that tourism brings; that’s true whether it’s Brazil or Benidorm,” Font told The Guardian. “Places like the Red Sea are using so much water they need a desalination plant. So they put one in, but in the process they over-salinate that area and kill the coral.”

If the warning signs are ignored, more irreplaceable cultural heritage sites could become little more than picture postcards for armchair surfers.

To see the entire 2010 Watch List, visit www.wmf.org