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Climate change, human activity rub salt into Venice's wounds

A woman looks on from a shop at the flooded St. Mark's Square, as high tide reaches peak, in Venice, Italy November 15, 2019. REUTERS/Flavio Lo Scalzo

ROME (Reuters) - Warming seas and excavations within the Venice lagoon mean the exceptionally high flood waters in the city this week are also saltier, posing an extra threat to its architectural treasures.

When the water recedes from the cobbled lanes, marbled palaces and ancient churches of a city that rose up out of marshes 15 centuries ago it leaves salt crystals which slowly corrode the brickwork and will eventually eat it away.

People walk in the flooded street during a period of seasonal high water in Venice, Italy, November 15, 2019. REUTERS/Manuel Silvestri

"With the salt water everything becomes more difficult for us," Mayor Luigi Brugnaro said on Friday as a fresh inundation left 70% of Venice submerged just three days after it suffered the worst floods in more than 50 years.

The lagoon has always held a mixture of water from rivers which feed it and that which enters via openings to the sea. Rising sea levels brought about by climate change and the digging of new canals and other structures mean more salt water is coming in from the Adriatic.

In the 1960s, a canal was dug in the lagoon for oil tankers to reach the petrochemical plant of Marghera, a port less than 5 km (3 miles) from the old center of Venice.

Waste from flooded households piled in the street caused by days of severe flooding in Venice, Italy, November 16, 2019. REUTERS/Manuel Silvestri

More recently, moon-shaped piers built to protect the gaps of the Venice lagoon were reckoned by the scientists of the National Center for Research (CNR) to have created big depressions in the sea bed, which would also allow more sea water in.

"The excavations of canals, in particular the one dedicated to oil tankers, have opened highways to the sea," said Gianfranco Bettin, former deputy mayor of Venice and long-time leader of the Greens in the Veneto region.

"Global warming has contributed by increasing the sea level and the strength of the winds that push the water towards the city," he added.

Tourist walk on the walkway in the flooded street during a period of seasonal high water in Venice, Italy, November 15, 2019. REUTERS/Manuel Silvestri

The main concern centers on Venice's Byzantine St. Mark's Basilica, with its ancient mosaics and marble columns, which are especially fragile.

On Tuesday the nave of church was flooded for the sixth time in 1,200 years and the second in just 13 months. The saltwater almost filled the crypt, whose marble columns support the church.

"The water was not supposed to inundate the crypt after work to seal it undertaken in the 1990s. But the tide was so high that the water poured in through the window," said Pierpaolo Campostrini, curator of the UNESCO world heritage church.

A man walks on the flooded street during a period of seasonal high water in Venice, Italy November 15, 2019. REUTERS/Manuel Silvestri

Campostrini, who is also an academic at the city's Ca' Foscari University, talked to Reuters on Friday while trying to reach the huge St. Mark's Square once described as Europe's living room.

"If the crypt becomes a swimming pool, we'll face an unknown situation," he said, as water was pumped out of the basilica. "The salt could cause a collapse of the vault, a risk that nobody wants to take."

A woman clears away damage caused by days of severe flooding in Venice, Italy, November 16, 2019. REUTERS/Manuel Silvestri

(Reporting by Giselda Vagnoni; editing by Philippa Fletcher)

Men have a glass of wine at a flooded street in Venice, Italy November 15, 2019. REUTERS/Flavio Lo Scalzo
A boat tries to pass under a bridge during a period of seasonal high water in Venice, Italy, November 15, 2019. REUTERS/Manuel Silvestri
People walk on a catwalk in the flooded street during a period of seasonal high water in Venice, Italy November 15, 2019. REUTERS/Manuel Silvestri
A view of the flooded street is seen during a period of seasonal high water in Venice, Italy November 15, 2019. REUTERS/Manuel Silvestri
A man removes water from the flooded shop during a period of seasonal high water in Venice, Italy November 15, 2019. REUTERS/Manuel Silvestri
A man cleans the floor after flooding inside the weaving workshop of Tessitura Bevilacqua in Venice, Italy, November 15, 2019. REUTERS/Manuel Silvestri
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