Trees can shield historical monuments and artwork from damage by air pollution, according to research at a villa built in Rome during the Italian Renaissance.
Particulate matter emitted from car brakes can be highly damaging to historical monuments and artwork. Over time, it accumulates on surfaces, creating dark layers and discoloration that often result in irreversible damage.
This is a particular problem for cities like Rome, which are both rich in historical art and monuments, and highly polluted.
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In the search for solutions, at the National Institute of Geophysics and Volcanology in Rome and his colleagues decided to monitor the role trees could play in reducing the impact of such pollution on the artwork in the . The villa, in central Rome, was built early in the 16th century. It is famous for its frescoes, many of them created by the virtuoso painter Raphael and regarded as masterpieces of the era.
鈥淰illa Farnesina is the perfect place to do this kind of study because it houses these fantastic historical works of art and it鈥檚 in an urban area that has a lot of vehicle traffic,鈥� says Winkler.
Along with his colleagues, he tested whether the leaves of trees in the nearby road and in the villa鈥檚 gardens accumulate vehicle particulate matter emitted from the busy street traffic, preventing it from reaching the frescoes inside the building.
They used magnetic bio-monitoring techniques to assess the level of air pollution. Their method is based on a simple principle: the leaves of a tree in a non-polluted area should have very weak magnetic properties, if any. But as they accumulate iron-rich particulate matter emitted听by cars, their magnetic properties intensify. The particulate matter comes mainly from car brakes, which are .
Inside the villa, where there are no trees, the team placed lichens (Evernia prunastri) in various rooms. They also placed lichens outside with the trees, and left them for three months in order to see how distance from the street and proximity to trees affects pollutant levels.
The researchers found that the tree leaves and lichens outside the villa were up to 40 times more magnetic than the lichens inside, indicating that the trees had a role to play in stopping particulate matter reaching the inner rooms of the villa and its artwork.听They also found that the pollutant levels increased the closer the lichens were to the road, confirming that the artwork was more at risk the closer it was to the road.
is known as a highly effective and low-cost way to measure air pollution levels, but the Villa Farnesina study is the first time this method has been deployed as part of historical art conservation efforts.
The researchers also found differences between how effectively different tree species can capture pollutants. For instance, the high magnetic readings recorded in the villa鈥檚 evergreen cypress trees suggest they offer better protection than its plane trees.
鈥淓ach tree species has a different ability to accumulate and store particulate matter,鈥� explains Winkler. 鈥淭he next thing to do is to study which types of trees we should be planting and where in order to maximise their protective effects.鈥�
Plans are under way to conduct a similar study at two of the city鈥檚 other historical sites, the Colosseum and its neighbour Palatine Hill 鈥� an area rich in archaeological ruins from ancient Rome. While the team is enthusiastic about the potential of trees for cultural heritage preservation, Winkler emphasises the need to think about root causes as well.
鈥淎t the end of the day, the best prevention is to reduce the number of cars on the road in the first place, especially in city centres,鈥� he says. 鈥淏ut when this isn鈥檛 possible, trees can be an excellent remedy for mitigating the damaging effects of air pollution on historical monuments and artwork.鈥�
Science of The Total Environment
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