For centuries, Europe's monuments have withstood earthquakes, fire and plundering. Now cultural treasures from the Colosseum to Westminster Abbey could face new threats from climate change, a study says.
Increased rains in northern Europe could wash away layer after layer of ancient stone, while rising heat in southern and central Europe could lead age-old monuments to crack and disintegrate, according to the European Union-funded study.
Experts have long warned that a rise in sea levels attributed to global warming threatens low-lying areas, including treasures like Venice or sites in flood-prone regions.
But the three-year study didn't look only at the catastrophic impact of storm surges, landslides and floods. It also took into account the slow erosion that Europe's cultural heritage could suffer from climate change, said Cristina Sabbioni, the study's coordinator.
"We needed to put this problem on the table, because so far it has been politically ignored," said Sabbioni, a physicist with Italy's National Research Council.
Climatologists, chemists, geologists and biologists used projected climate data to predict how marble, limestone, wood and other materials commonly used in ancient buildings would fare in future weather patterns until 2099, Sabbioni said.
Researchers produced a "Vulnerability Atlas" of Europe, with maps that indicate which areas will suffer an increase or decrease in risk factors, from damage caused by salt crystals to corrosion of medieval stained-glass windows.
Gothic cathedrals especially at risk
According to the study, lower humidity during the summer in Britain, France, northern Spain and central Europe will increase the amount of salt deposited on monuments.
This is especially dangerous for the region's Gothic cathedrals, whose elaborate carvings are made of soft porous stone which absorbs sea salt from the air. Once the water evaporates, the salt crystallizes and puts pressure on the surrounding stone, Sabbioni said.
"If the salt is deposited on the surface, the damage is aesthetic, and this is a dramatic problem for frescoes," she said. "But if it is absorbed we have internal breakup of the material."
Less rain in southern Europe will force authorities to spend more money to clean monuments blackened by pollution, while an expected rise of precipitation in northern Europe could wash away an increasing amount of ancient stone each year.
Monuments built of marble and limestone, such as the Colosseum in Rome and the Parthenon in Athens, will also suffer due to increased temperature fluctuations which cause such materials to expand and contract, causing fractures and breakage. Central Europe, southern Spain and Greece will be the areas most affected due to the drier climate and rising temperatures, the study says.
Even more recent monuments like the Eiffel Tower, completed in 1889, could face trouble as the study predicts warm weather and pollution will increase corrosion of metals in northern Europe.
Researchers said problems caused by rain, salt crystallization and thermal stress are already known to conservation experts. For example, the baroque facades and statues of the southern Italian town of Lecce, carved in soft stone, have long been eroded and damaged by rain, pollution and salt.
But the study indicates these threats will move to areas where they were previously unheard of, said Joseph King, an official with the International Center for the Study of the Preservation and Restoration of Cultural Property, a U.N.-backed intergovernmental organization based in Rome.
"Climate change touches a lot of things, and cultural heritage is among them," said King, a conservation expert who did not take part in the EU study. "The problems we are going to have are the same ones we have now. The difference is in the intensity and where they are going to occur."
Not all the study's predictions are negative. Glass corrosion is expected to decrease across Europe and reduced moisture will help bricks in historical buildings stay dry.
Sabbioni warned the effects could ultimately be even worse because the climate model used for the study was a "moderately optimistic" one chosen from among those used by the U.N.-sponsored Intergovernmental Panel on Climate Change. The agency issued a spate of reports this year, drawing on the studies of some 2,500 scientists, which predict grim consequences of global warming if swift action is not taken.
Although no specific research was done on single monuments, the maps produced by the $1.6 million "Noah's Ark" study on climate change and cultural heritage can help policy-makers plan conservation efforts based on which risk factors threaten their area, Sabbioni said.
The study offers guidelines to help limit the effect of climate change on monuments, from increasing the frequency of repairs to installing barriers on buildings to reduce salt deposits.
Researchers didn't produce an estimate of the cost of climate change on cultural conservation, but the study says that, ultimately, Europe may have to accept some losses.
"Priorities will have to be established," Sabbioni said. "We cannot hope that everything will last forever."