The old city of Dubrovnik, clinging to the Croatian coast of the Adriatic Sea, is just one major storm away from a flood that could cover 10 per cent of a city that was a main setting for Game of Thrones.

The medieval city long known as the "Pearl of the Adriatic" It's just one of some 40 treasured historical sites across the Mediterranean at risk from rising seas, according to a new study published today in the journal Nature Communications.

Others include the winding canals of Venice and the ancient city of Carthage.

The reason for their sweeping vulnerability is the same one that fostered so many civilisations in the Mediterranean to begin with.

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It's the lure of the sea, dating back at least to the time of the ancient Phoenicians, who set sail from the now threatened sites of Byblos and Tyre along the current coast of Lebanon.

"That's just classic Mediterranean history," said Joseph Manning, a professor of ancient Greek history at Yale University, who praised the new research. "Everything is within two miles of the coast."

But now, numerous Roman ruins, the original site of Carthage, historic regions of Istanbul and many other landmarks left by cultures ranging from the Phoenicians to the Venetians could be flooded in extreme storm events, or face growing erosion risks, said the research.

"What surprised me the most is that actually even under current conditions, there are so many world heritage sites that are at risk," said Lena Reimann, a researcher at Kiel University in Germany and a lead author of the study.

In a world of rising sea levels, those risks will grow only more severe, threatening the destruction of irreplaceable cultural landmarks.

"We cannot put a value on what we will lose" if action isn't taken to protect such sites, Reimann said. "It's our heritage - things that are signs of our civilisation. It cannot really be put in numbers. It's more an ethical question, a moral question. We will not be able to replace them once they are lost."

The study used the database of Unesco World Heritage sites and projections of future sea level to arrive at its conclusions. It found that out of 49 total such sites along the coasts of the Mediterranean, 37 are already vulnerable to a 100-year storm surge event.

Venice's canals draw millions of tourists.
Venice's canals draw millions of tourists.

Many of the most at-risk sites were along the Adriatic Sea and included not only Venice but also the early Christian monuments of Ravenna, and the archaeological area and patriarchal basilica of Aquileia.

A closer look at the archaeological area at Aquileia gives a hint of just how much is at stake. Here, according to Unesco, an ancient city "still lies unexcavated beneath the fields, and as such it constitutes the greatest archaeological reserve of its kind." In other words, a historical site that hasn't even been uncovered yet could be damaged or lost.

For Yale's Manning, rising seas could be the next destroyer of human culture to come along after massive losses in the past decade alone tied to violence and civil war in Syria, Iraq, and Egypt, among other countries.

"In terms of cultural heritage in the last decade, it's actually shocking, it's alarming and depressing," he said.

The largest number of vulnerable sites, the study found, were located in present day Italy. Croatia, Greece and Tunisia also have a large number of sites within their present borders.


The risk only increases as sea level rises for these sites, and the study also calculated an additional, related erosion risk at 42 of them. This, too, will worsen.

The central reason for so much vulnerability, the research notes, is simply that human civilisations, as they emerged in the Mediterranean (and elsewhere), have traditionally clustered near water. It offers many advantages, ones quickly exploited by the far-ranging Phoenician sailors and numerous other local cultures.

The problem is that while sea level rise has been slow for the past 3000 years, it has accelerated over the past century as human-driven climate change has commenced, and the 21st century is projected to outdistance the last 100 years by a large margin.

Reimann said a handful of places - including Venice, which is putting in place a mobile barrier system to help guard against floodwaters - have poured time and money into finding ways to adapt. But such sites are in the minority.


"We couldn't really find any other examples across the whole Mediterranean region where adaptation measures were pursued as much as in Venice," Reimann said.

National governments are charged with caring for world heritage sites. But Reimann said that while there are regionwide sustainability efforts, those policies don't deal specifically with vulnerable cultural sites.

"When you go over the management plans [for these sites], there are just a few that mention sea level rise as a threat," she said, adding, "There are many sites where adaptation is urgently needed."

The United Nations itself has recognised the precarious nature of many heritage sites amid the changing climate, saying that "their continued preservation requires understanding these impacts," as well as "responding to them effectively."