That sinking feeling: What would the death of Venice mean for all of us?

Even if you have never been to Venice, it sometimes feels as if you have. Its exotic beauty is sourced by everyone, from novelists and film directors to painters and architects. Across the globe, countless "little Venices" have been created in its image.

When a piece of masonry fell off the Doge's Palace in St Mark's Square in 2007, it was as if the bedrock of Western civilisation had shuddered. Yet part of the allure of the city built on water has long been the notion that it was doomed to sink beneath the waves. To Charles Dickens, the Grand Canal was a coiled serpent waiting to uncoil itself and drag Venetians into its depths. In his influential three-volume The Stones of Venice, published between 1851-53, John Ruskin wrote of her "in the final period of her decline... bereft of all but her loveliness", losing the battle against the fast-gaining Adriatic.

Victorians primarily worried about the crumbling Venetian architectural heritage, with its remarkable fusion of Western Gothic and Eastern Byzantine stylistic influences. They attacked well-meaning, but heavy-handed, attempts at "restoration". But as a compelling new book by Robert France shows, modern conservationist anxieties run deeper. Veniceland Atlantis, part photo-essay, part polemic against decades of bureaucratic neglect and a carnivorous tourist sector, reveals that the "death of Venice" is linked to broader concerns about the environment, climate change and tourism.

"In Venice, as perhaps in no other city, one is intimately exposed to nature," France says. It is, he says, "the world's most naturalised city at the same time that its lagoon is possibly one of the world's most famous culturalised pieces of nature".

While most cities were built in strategically important, but accessible, locations, Venice was established in the fifth and sixth centuries as a retreat from the barbarian Hun and Lombard invaders precisely because of its inconvenience. Its lagoon and marshes rendered it impenetrable to attackers from the land, but the waters were equally too shallow for a sea offensive. The city was steadily developed by consolidation of the salt marshes, its buildings supported on wooden piles driven into the sandy bed and resting on foundations of durable, non-porous Istrian stone.

By the medieval period, the city's population was up to 10 times that of Paris, London and Rome, yet Venetians lived in constant fear that the lagoon, acting as a defensive moat, would silt up and disappear. So they waged constant war to modify the effects of the inflowing water.

According to France, this has created an uneasy equilibrium. The lagoon is the largest wetland in Italy and one of the most important areas of avian abundance and diversity in the Mediterranean, but it is an artificial construct that, without repeated human intervention, would have long since disappeared. Now the signs are that time is running out, as graphically illustrated by the photographs of France, an environmental scholar who spent three summers in the city while researching and writing the book.

He doles out some gloomy statistics. From a combination of factors, including natural subsidence, the dredging of deeper shipping channels to enable large containers to access the Venetian port and the general rise in sea levels, the instances of Acqua alta – the moments when tide peaks in the lagoon flood the centre of the city – increased from 385 in the 1920s, to 2,464 in the 1990s. Eight of the most extreme examples have occurred in the last 40 years and St Mark's Square, which used to flood 10 times a year on average, can now be expected to do so 100 times.

Such effects have a wider significance, France says. "Sea levels around the world are predicted to rise anywhere from eight to 88cm by the start of the next century. Due to being built flush with the water, Venice is the first major Western city to face sea-level rise as a consequence of climate warming. The present conditions in Venice are therefore a presage of what the future might bring elsewhere."

There are no more evocatively pitiful images in his book than those of the city's flaking and crumbling canalside buildings. Istrian-stone foundations may have low porosity, but the stucco and brick of the buildings above do not. As the salt waters creep upwards, the stucco peels, the bricks erode and gaping cracks develop, shored up by makeshift wooden splints, lattice and crutches. The situation has deteriorated to the extent that Anna Somers Cocks, chairman of the British charity Venice in Peril, warns: "The damp has risen to six metres in the atrium of St Mark's, the point at which it is causing mosaics to fall off the walls."

In 2003, after decades of argument and procrastination, work began on Mose, a project to build a system of submerged floodgates which, when high waters are forecast, will rise to block off Venice and its lagoon from the Adriatic. Costing over €5bn (£4.5bn), it is one of the most expensive marine engineering projects in history. France says that it will save Venice from the worst of Aqua alta in the short term but, with a shelf life of around 60 years and rising seas levels expected to put a further time limit on its effectiveness, he says that cheaper options might have been just as successful.

Somers Cocks argues that Mose will do nothing to stop the chronic rise in mean water levels in the Venice lagoon, predicted to increase by a minimum of 50cm by the end of the century. "The barriers will hold back the worst of the floods, but you couldn't keep the gates closed all the time without serious ecological consequences," she says. Dante may once have written of having difficulty walking through the Venice delta, so lush was its vegetation, but 20th-century industrial development along the mainland coast and agricultural intensification have come at the expensive of the wetland environment and the canal waters in which some tourists are eager to paddle are highly toxic.

"The lagoon has to be sluiced out twice a day because the water flowing into it from the surrounding rivers is full of phosphates and fertiliser run-off and, until recently, waste from the petro-chemical factories," Somers Cocks says. And Venice is one of the last major Western cities to still be relying on a medieval system of drainage. "Effluence is pumped straight out into the canal, so keeping the gates permanently closed would only make a bad situation worse," she says.

On top of these issues, France and Somers Cocks point to the failure of local, regional and national governments to adopt a long-term strategy to deal with the ever-growing number of tourists or the shrinking local population. Last November, Venetians staged a protest at the rising cost of living in their city and its transformation into a Disney-like Veniceland, arguing for the levying of a tourist tariff.

Many have long since abandoned the place to live in cheaper, more modern accommodation on the mainland, leaving behind what is now the oldest population (average age 48) in Europe. A Unesco director has stated that "Venice has become a museum city, no longer a residential one".

Somers Cocks has a less fatalistic view, pointing to the three universities in Venice and the vast areas of the city, currently derelict, which could be renovated to provide subsidised housing to encourage middle and low-income earners to move back. "Instead, the council have allowed properties to be converted into low-grade B&Bs, which has driven prices up," she says.

"They have also transferred government offices on to the mainland – whereas a managed policy of retaining them in the centre would help it retain its vibrancy."

Recently, the Mayor of Venice finally spoke out in favour of a tourist tax, but Somers Cocks see no evidence of real change to the current laissez-faire approach, with entrenched political divisions between a left-wing local government and a right-wing regional one standing in the way of a co-ordinated strategy. She argues for the EU to step in to save what is, after all, a designated World Heritage Site. "We have to accept that Venice will always be expensive to maintain and will get more so. But the city has a non-pecuniary worth in the way it is esteemed and valued and Europe has to wake up to that. There needs to be a body above the political fray which is able to provide the continuity of governance Venice needs."

France, too, suggests other options, including the designation of Venice and its lagoon as a national park or a greater emphasis on cultural tourism. The latter seems unlikely, given mass tourism remains such a cash cow. Horribly, he imagines a scenario years from now when a bankrupt Italian government sacrifices Venice entirely to "theme park" tourism, with visitor numbers capped at 50 million per year – it is struggling to cope with the current "tourist tsunami" of 17 million a year.

France's book is required reading for anyone who cares about the future of the beloved city. "Now may be the last chance to save the real Venice, while there is some reality left to be saved," he says, with tangible anguish. "But is anybody in Italy listening?"

'Veniceland Atlantis' is published by Libri (£17.99). To order a copy for the special price of £15.69 (free P&P) call Independent Books Direct on 08430 600 030, or visit www.independentbooksdirect.co.uk