The lagoon city risks “losing its soul” as it struggles to cope with 60,000 tourists a day, nearly double the number it can sustain, according to Italia Nostra (Our Italy).
Campaigners say Venice should discourage mass tourism and instead court high-spending visitors. The city could also encourage activities like university research and technology.
The environmental group said the threats faced by ‘La Serenissima’, as the Venetian republic was once known, were so grave that UNESCO should consider striking the city off the World Heritage list.
“The Italian government has not lived up to its commitment made to UNESCO to safeguard Venice and its lagoon,” the organisation said. Alessandra Mottola Molino, Italia Nostra’s president, said: “We need to launch a planetary alarm.”
Sea level rises and more frequent storms are expected to increase the level of the Venetian lagoon by 20 inches by the end of the century, threatening to undermine the foundations of centuries-old palaces and churches and swamp some parts of the city altogether.
High tides, particularly during the winter, already flood much of the city, including St Mark’s Square, the focus for millions of tourists.
The situation was exacerbated by the increasing number of giant cruise ships which visit Venice – their wake erodes the delicate mud banks and wooden piles on which the city is built, Italia Nostra said.
Dredging, landfill and the construction of a huge new satellite city on the Italian mainland, a few miles from Venice, are radically changing the lagoon’s ecosystem and posing enormous risks to the survival of one of the world’s most beautiful urban environments.
Cristiano Gasparetto, a former member of the city’s Commission to Safeguard Venice, said the proposed construction of a six-mile-long underwater subway linking the mainland to Venice risked becoming an “ecological disaster”.
“If we lose the lagoon, we lose the city,” he said.
In an attempt to save the city, Italians are building a £3 billion flood barrier, named Moses, consisting of 78 giant steel gates across the three inlets through which water from the Adriatic surges into Venice’s lagoon.
The project, due to be operational in 2014, will like its namesake literally turn back the waves, regulating the flow of water from the sea.
But for all its expense and technological sophistication, it will only be a stopgap measure, environmentalists fear.
“In 100 years the sea level will be such that the barriers will have to remain closed all the time, blocking the natural exchange of sea water that is (the lagoon’s) very life source,” said Lidia Fersuoch, the head of Italia Nostra’s Venice chapter.
“This will change Venice as we know it.”