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From NPR News, this is ALL THINGS CONSIDERED. I'm Audie Cornish. In its heyday, Venice, Italy, was known as the pearl of the Adriatic. Today, the unique lagoon city is a fragile architectural treasure endangered not only by rising sea levels and mass tourism. As NPR's Sylvia Poggioli reports, the city and its canals are also being invaded by ships as big as skyscrapers.
SYLVIA POGGIOLI, BYLINE: On an average day, tens of thousands of passengers lean over the railings of giant cruise ships three times the length of a football field and 15 stories high. The tourists peer down at the majestic Doge's Palace as they sail into St. Mark's basin and down the Giudecca canal.
Matteo Casini, a professor of history, says the big ships are alien creatures and an insult to the Renaissance jewel.
MATTEO CASINI: It's like being in a science-fiction movie or - I don't know - this monster, they obscure us. They are twice the Palazzo Ducale. They are longer - twice the Piazza San Marco. They have dimensions and numbers nothing to do with Venice.
POGGIOLI: Casini complains that when big ships pass by, windowpanes tremble and vibrations lead to cracks in the walls of old buildings. He complains that the towering ships interfere with television and Wi-Fi signals.
Last month, exasperated Venetians organized a three-day protest under the slogan Take Back the Lagoon. The high point was a symbolic boat blockade in which hundreds of people in small vessels filled the canal, waving banners with the words No Big Ships.
UNIDENTIFIED GROUP: (Chanting)
UNIDENTIFIED WOMAN: (Foreign language spoken)
UNIDENTIFIED MAN: (Foreign language spoken)
POGGIOLI: Big ships are destroying Venice, a woman laments over a loudspeaker. And a man proclaims, each big ship spewing black smoke pollutes the equivalent of 14,000 cars, moves 135,000 tons of water and destroys the foundations of Venetian buildings.
Cruise ship tourism in Venice has gone from under 100,000 passengers in 1999 to 1.8 million in 2011. More than 650 big ships arrive annually. Six ships docking at the lagoon terminal can disgorge in one day more than half the city's population of 55,000.
History professor Matteo Casini says these rapidly growing numbers of tourists are causing irreparable harm.
CASINI: Tourism cannot alterate(ph) the nature of the city and the lagoon. Venice is not a Disneyland.
POGGIOLI: But tourism is the bedrock of Venice's economy and not everyone here wants the ships kicked out of the lagoon.
PAUL PATTISON: When there are boats in, you can feel the difference. Boats make that difference, that 15 to 20 percent difference. You feel it. There's no doubt about it.
POGGIOLI: Paul Pattison is half-British, half-Venetian. His family's blown-glass factory is profiting from the cruise ships. He dismisses the negative psychological impact of seeing the big boats tower over the city.
PATTISON: I find it fantastic. It's almost like reliving a Fellini film every single day, and that's great.
POGGIOLI: It's hard to get reliable data on just how much the cruise industry brings into city coffers. Many critics claim that by living on board, ship passengers just buy some souvenirs and that hotels and restaurants do not profit from their presence.
One organization that has reaped the benefits is the Venice Port Authority, which manages the docks. Its head, Paolo Costa, says the cruise industry has created 6,000 jobs. He says saving Venice does not mean just saving its monuments.
PAOLO COSTA: We have to protect even the life in Venice. It's not just some trivial jobs. It's the essence of Venice. Venice without a port does not exist. Venice was a historical maritime republic.
POGGIOLI: Costa wants to widen an existing canal in the lagoon to prevent ships passing too close to historical buildings. But Anna Somers Cocks, former chairman of the Venice in Peril Fund, says that would cause serious damage to the lagoon's delicate ecosystem.
ANNA SOMERS COCKS: Because it contributes to the creation of a very strong current when there is a low tide which sucks out sediment from the bottom of the lagoon. And the lagoon used to be quite shallow and very still and is now getting very deep because it's losing sediment the whole time out into the Adriatic Sea.
POGGIOLI: Opposition to the big ships grew after the Costa Concordia cruise ship ran aground off a Tuscan island 18 months ago, killing 32 people. That prompted a government ban on big ships sailing too close to the coast. But the decree was suspended for Venice until an alternative could be found.
In response to the growing outcry against big ships, the government, the municipality and the Venice Port Authority have finally agreed to search for alternative solutions. Sylvia Poggioli, NPR News.