The integrity of dozens of coastal towns of the Mediterranean declared World Cultural Heritage of Humanity is in danger. A study published on Tuesday Nature Communications shows that most of these sites are threatened by rising sea levels, one of the consequences of global warming. The research assesses how the combination of this factor with extreme weather events can cause an increase in erosion and coastal flooding. In total, up to 47 of the 49 analyzed places they could suffer negative impacts by one of these two phenomena (or both), as he concludes. The authors consider it necessary for governments to take appropriate measures at each site to guarantee the protection of these places.
Some Mediterranean sites declared World Heritage sites already suffer the impacts of rising sea levels, explains Lena Reimann, a researcher at the University of Kiel (Germany) and lead author of the study. An emblematic case is the Laguna de Venecia, subject periodically to partial flooding. In this Italian city, for the last fifteen years a barrier system that would reduce the impact of high tides, explains the scientist.
Things in the Mediterranean will not improve, as evidenced by the projections of climate change in the region. "The main threat will be represented by the coastal floods," explains Reimann. "Sea levels will be more extreme, with buildings, churches, temples and statues clearly threatened," he says. "Coastal erosion is progressing more slowly, but it could affect certain structures, as well as the characteristics of cultural landscapes such as the Po Delta (Italy)," he adds.
The investigation proposes for the year 2100 four possible scenarios of rising sea rise in combination with extreme events. For each of the sites analyzed and for each scenario, the study compares the situation in 2000 with how it could have evolved a century later. The authors predict that, in the most unfavorable case, the sea level would rise by one hundred years of up to 1.46 meters. As a consequence of this phenomenon, floods in the Mediterranean area could increase up to 50% and coastal erosion up to 13%. The final result of the study is an index of exposure to erosion or flooding of each of the places taken into consideration.
In Venice the Sperimentale Elettromeccanico Module (MOSE) began to be built in 2003, a system of barriers that would prevent the flooding of urban areas if the level of the high tide exceeds 1.1 meters. The works are completed at 94-95% and are expected to be completed within this year, according to Venezia Nuova sources, the consortium in charge of construction by the Italian Ministry of Infrastructure and Transport. Currently, one of the four barriers envisaged in the MOSE is already in operation, according to the same sources. The final implementation of the project is scheduled for the end of 2021 after a period of testing, they add.
"With regard to the risk of flooding, some of the most extreme conditions can be found in the northern part of the Adriatic Sea, which hosts many sites declared a World Heritage Site," says Reimann. "This area includes Venice and its lagoon, Ferrara and the delta del Po and St. Jacob's Cathedral in Sibenik (Croatia)," he explains. The results referring to the increase in the erosion conditions of the coasts, on the other hand, show that the three most vulnerable places to this phenomenon are the archaeological jewels of Tire (Lebanon), Tarragona and Ephesus (Turkey).
The countries with the highest percentage of world heritage threatened by rising sea levels are Italy, Croatia, Greece and Tunisia, according to the study. For Spain, in addition to Tarragona, the Sierra de Tramontana in Mallorca is taken into consideration. In the case of this site, the research indicates a particularly high rate of exposure to erosion. Only the Medina of Tunis (the old town of the capital of the North African country) and the ruins of Xantos-Letoon (Turkey) do not appear at risk of impacts due to erosion or flooding.
How to face the tide
Unesco sources say that climate change is "a growing threat" to sites declared World Heritage. "The impacts are varied, and the rise in sea level is just one of them," they add. In 2017, a study conducted by the International Union for the Conservation of Nature He noted that the number of natural places impacted by climate change had doubled in three years. "The situation is not very different for cultural sites," compare the sources cited above.
To deal with the situation, the authors of the study published on Tuesday believe that protection measures are needed adapted to the characteristics of each of the threatened places. Therefore, they argue the need to conduct studies focused on the situation of each one. "You can imagine a classification of sites where similar strategies can be applied," says Reimann. "But a solution that works for everyone does not seem plausible," he adds. In his opinion, "early planning and proactive adaptation, including innovative solutions for different sites" are needed.
The countries that concentrate the highest percentage of the world heritage threatened by rising sea levels are Italy, Croatia, Greece and Tunisia
For its part, Unesco states that the underlying issue remains the need to reduce CO emissions.two and limit the average increase in global temperature "at least below 1.5 degrees Celsius", as established in the Paris Agreement on climate change. If governments do not achieve these goals, "the future of much of our sites declared world heritage will be bleak," he warns.
Íñigo Losada, Professor of Hydraulic Engineering at the University of Cantabria, points out that the new study does not consider the specific characteristics of the included sites in its analysis. In the opinion of this expert, this constitutes a limitation, because the results of the effects of floods and erosion illustrated for each place could be overestimated. "A flood does not affect a cathedral or archaeological ruins in the same way," he explains. The professor also emphasizes that it is necessary to evaluate that some of these elements are protected by being in a city or will be protected by defense structures, as in the case of Venice.
Despite these observations, Losada considers undeniable that the rise in sea level is a real danger for many coastal locations in the Mediterranean, including sites declared World Heritage. "In terms of climate change, our most exposed universal heritage is that located on the coast subject to the impacts of flooding and erosion," he says.
The expert adds that in the Spanish Mediterranean coast there are also many sites of historical or cultural value that are threatened but not included in the Unesco list. "We know that we are going to have more erosion and more floods. We should lend this heritage the same attention we dedicate to cities, infrastructure or ecosystems, "he concludes.
Agustín Sánchez-Arcilla, professor at the Polytechnic University of Catalonia (UPC), explains that in this region vulnerability to coastal erosion is due in particular to the lack of sand. "It is a scarce resource and you have to handle it with a lot of intelligence and caution, otherwise you will not get well stopped," he says.
The expert says that a research group at the UPC is experimenting with an innovative method of protecting the coast from rising sea levels based on the use of this material. The sand is used to fill bags of natural fiber and thus create a type of barrier different from stone, because it is flexible and adaptable to possible increases in water levels, explains Sánchez-Arcilla. You can also easily change your location if the coastline recedes, he adds.
The professor confirms that the area where the archaeological site of Tarragona is located, declared a world heritage site, is also very exposed to erosion. The system undergone by the UPC would be effective in protecting that coastline, he explains. The tests of this method are funded by the EU under the project Hydralab +.