France is not short of Unesco World Heritage sites but some appear to be more "must-see" than others thanks to the threat that they will one day disappear under the sea if global warming continues.
If the current warming trend continues and temperatures rise to 3°C above pre-industrial levels over the next 2,000 years—a likely scenario—136 Unesco sites would be impacted, the researchers wrote.
These sites are currently protected against development or destruction, but not against the affects of continued global warming.
Using sea level rise estimates and topographic data, the researchers at University of Innsbruck and the Potsdam Institute for Climate Impact Research looked at the impact of rising sea levels in different countries over the next two millennia.
Ben Marzeion, study author and climate scientist at the University of Innsbruck, told The Local previously the cultural impact of global warming had been relatively ignored;
"When thinking about climate change, people usually think about ecological and economic consequences," he said.
"We wanted to add another dimension: what might the cultural impacts be? Culture is hard to quantify, but for the Unesco list there is general agreement that these sites are significant and worthy of special consideration and protection," he explained, adding that Unesco had not funded the study.
Historic sites are also under threat across Europe, including the Hanseatic hubs on the German Baltic coast, the town of Visby and the port of Karlskrona in Sweden and the historic cathedral of Seville in Spain.
The researchers in the study published in the journal IOP science recognized the difficulty of making models of climate change, and also admitted they hadn't taken into account local conditions like flooding, but they said the consequences of inaction could be disastrous.
"Our analysis illustrates that the spatial distribution of the existing and potential future cultural world heritage makes it vulnerable to sea-level rise," the study authors wrote.
"Future generations will face either loss of these sites, or considerable efforts to protect them," they warned.
While Marzeion conceded he was not a specialist on coastal protection, he did tell The Local that technical solutions including "the building or upgrading of dykes" might be possible for some sites.
However "for some sites it will be hard to do anything at all — particularly in those places where the site is directly on the shore line," he added.