One textbook example is Spain's Costa del Sol—the overbuilt "Costa del Concrete," which caters to package tours from northern Europe, and where you can hear more English or German than Spanish. As with many uncontrolled seashores, a nonstop line of characterless hotels blocks off the coastline. Proving such a tide can be turned, one Majorcan town has now razed a few hotels.

On any attractive shore, if no policies exist to cluster mass-tourism hotels, or preserve traditional towns and open space, resort sprawl tends to take over. Community leaders in a few such destinations have begun to recognize the problem, asking how best to handle hordes of tourists who are more interested in sun, rum, and each other than in the country they happen to be visiting.

Different threats place other low-scoring destinations at risk: excess popularity (the Acropolis and the Great Smokies), political or civil strife (Bethlehem), poorly planned mass sightseeing (Angkor), encroaching urban development (the Pyramids), inappropriate tourism development (Great Smokies again—i.e., Gatlinburg), even sea-level rise from global warming (Venice).

This Stewardship Index is intended to be a wake-up call. Low-scoring places can learn from high-scorers. Often, though, it's very, very late in the game. Jamaica's resort town of Negril, for instance, has a vigorous reef-restoration program—now that as much as 90 percent of its reef has died, due to both local and global factors.