Global tourism is growing rapidly, propelled by rising prosperity, cheap airfares and the ease of online booking. But many destinations, from the canals of Venice to Arizona's Grand Canyon, are struggling to accommodate hordes of visitors. In Amsterdam and Barcelona, residents are blaming “overtourism” for congestion, pollution and escalating rents, and U.S. national park superintendents say crowds and vehicles are damaging precious sites such as Yellowstone and Yosemite. But the travel industry and many government officials say curbing tourism would harm the economy. The industry accounts for some 118 million jobs worldwide and a significant percentage of economic activity in many places. To deal with tourism's pressures, some destinations are limiting the number of visitors, while others are fining drunken behavior, raising tourist taxes, restricting short-term vacation rentals or steering visitors to less crowded sites. Meanwhile, critics say “sustainable tourism,” a niche aimed at protecting a locality's environment and cultural heritage, can have negative consequences by spawning development that changes a destination's character.