TOThis year too, the delightful colors of autumn arrived a little late on schedule. When the cold weather delays, deciduous trees in the city slow down their preparations for winterwhich consist of withdrawing the precious green chlorophyll from the leaves, which are thus tinged with yellow, orange and brown, before falling to the ground and leaving the plant to relax in winter.
In times of climate changethe hope is that this vegetative rest is not afflicted by the vagaries of the climate, capable of even felling majestic monumental trees. As happened on 25 July 2023 when a storm of unprecedented violence broke out in Milan, with winds at over 100 km per hour and 40 millimeters of water in 10 minutes, i.e. how much falls in a month. At dawn, the citizens discovered a massacre of trees: 4776 fell, of which 3838 in parks and 938 in rows along the roads.
Trees in the city, victims of climate change
«They were different trees in terms of typology, species, age, conformation» recalls Elena Grandi, councilor for the environment and greenery of the municipality of Milan. “The wind also knocked down young and healthy plants.” This disastrous storm, unfortunately, was not a unique event. Increasingly, our cities are the targets of climate gone mad.
In 2023, theLegambiente City Climate Observatory recorded 378 extreme events, with Lombardy and Emilia Romagna at the top of the ranking. But there’s something for everyone: from Rome to Ravenna, from Palermo to Prato, the peninsula is in the crosshairs, the plants in the city are put to the test from drought and excessive summer heat, alternating with torrential rains and hurricane-force winds. You don’t need to be a scientist to understand that this makes trees weaker and more likely to fall.
By 2050, 70 percent of the world’s population will live in cities that will have to accommodate more and more trees if we want to mitigate heat islands, ensure oxygen, recreate green spaces for biodiversity but also for the mental and physical health of the inhabitants. In the face of now undeniable climate change, cities must adapt their tree heritage. How are Italian metropolises preparing to defend their trees? We interviewed the greenery managers of Milan, Turin and Rome.
New safer plants in Milan
The Alberi library in Milan. Photo: Laurie Anderson
Stronger than that 520 thousand trees managed directly by the Municipality or by other bodies, in Milan the replacement of those knocked down by the 2023 storm is underway. «Since November 2024 we have been working to replant them» explains Elena Grandi. «We didn’t do it immediately because a year ago, that is, at the beginning of the planting season, we weren’t ready. The trees had to be ordered from nurseries and prepared. We also made use of the Fund for trees: 1 million and 300 thousand euros coming from citizens and large donorswhich allowed us to focus on trees more than double the average size of those that are normally planted.”
It is an important factor: the larger the replacement plant, the greater the carbon storage, but also the shade and coolness it will immediately provide to people. «The goal is to replant all the trees lost even in the parks: 215 at Montanelli, 372 at Sempione, 510 at Forlanini». The agronomists of the Municipality, in collaboration with the university, have worked to identify the most resistant species. «The most present trees in Milan are maples (27440), followed by plane trees (22694) and lime trees (20777)», he points out Big. «We also have 11,870 elm trees, often old: many have fallen. Plane trees are resistant if well treated, but construction sites and illegal parking on the roots weaken the plants.”
The new trees will not be the same species as the previous ones, with the exception of replacements in historic gardens. «We tried not to place plants taller than 20 meters, but shorter ones which require less pruning. With fewer interventions, the tree remains healthier. The species? The hackberry, the gleditsia, the koelreuteria. Even that’s fine black locust, which is invasive, but resists well and has an important ecosystem function».
These changes, made to make the city safer and the greenery healthier, sometimes meet resistance from the public citizens, who must be informed to understand the reasons for the administrators’ choices. «In via Fabio Filzi we are replacing the entire avenue lined with elm trees, an innovative intervention. We carried out stability investigations on all the trees and almost 80 percent were in class D, meaning they needed to be cut down because they were at risk of crashing. We involved the inhabitants, traders, committees and now we are replacing the elms at risk with gleditsiawhich grow quickly.”
Trees in the city, new species in Turin
The heritage of trees a Turin amounts to 400 thousand specimens throughout the municipal territory, including the hilly areas. «The city is characterized by the presence of tree-lined avenues: 300 kilometers with 170 thousand plants» explains the councilor for Public Green Francesco Tresso. «Another peculiarity is given by passage of the Po with three tributaries. We have blue-green corridors lined with vegetation. The tree-lined avenues are nineteenth-century in style.”
Spring cityscape of Turin, Italy, taken from the Ponte Isabella, with the Po river, flowering trees and the Mole Antonelliana. (Getty Images)
Plants that once did well may present problems today. Tresso speaks of almost 4000 trees lost in the dry summer of 2022 and of 400,500 plants victims of the storms of 2024. «Beeches are beautiful, but suffer from a lack of water. And so do the hornbeams». But they are not the only ones. «The maples planted about 80 years ago are in a state of stress: there is the passage of the tram which forces continuous pruning for safety, cars park on the roots» comments the councilor, who, like his Milanese colleague, is working with the university to find species more adaptable to climate change.
Not only that: by replanting a new tree, work will be done on the bank – the earth around the trunk – to facilitate the absorption of rainwater and for better protection of the plant. «We have experimented with the flowering pear, which has a pleasant flowering and does not get too tall. And then we use plum trees, cherry trees, lime trees, walnut trees. The aim is to diversify for biodiversity and pathologies. If we planted trees of the same species, in the event of disease we would risk losing them all” he explains. As happened with the plane trees, affected in Turin by the colored cancer caused by a fungus. «The trees look healthy but they are sick and we had to cut them down» Tresso tells us. «We try to explain the interventions to the citizens.
Climate change can cause failures, sometimes unpredictable. The trees are mapped and every six-seven years we carry out a checkup. If there is even a minimal risk, we need to intervene. By replacing old specimens with new ones we try to create better conditions for growth». There depavingthat is, the elimination of asphalt, helps the city and its trees to breathe better. In Turin, thanks to the Pnrr, an intervention is underway at Valentino Park will free up 70 thousand square meters (equal to 15 football fields) from the asphalt, with more greenery and elimination of parked cars, which will end up in an underground car park. In case of rain, the water will be drained more effectively.
The microclimates of Rome
«Take care of the greenery of Rome also involves imagining what the city will be like in 20 or 50 years, in a changing climate that requires the city itself to change» observes Sabrina Alfonsi, councilor for Agriculture, Environment and Waste Cycle of Roma Capitale. Water bombs and violent storms have not spared even the eternal city, which has a heritage of over 300 thousand trees.
There are downy oaks, holm oaks, beeches, plane trees, turkey oaks but the symbol of the capital is the stone pine. «The pines are very old, because they were planted in the early twentieth century» explains Alfonsi. «The citizen’s perception is that they are more at risk of crashing than others, just because they are present to a greater extent in some areas than other species. They are delicate plants also because they are under attack by the turtle scale insect. For this reason, we monitor them with frequent checks. We have invested in care and at the same time we have replanted pine trees in the central area of the city.”
Villa Doria Pamphili. Rome. photo Nicholas Tinelli /Alamy / Olycom
Since November 2021, however, 18 thousand trees have been cut down. «Yes, but about a third were dry trees and weed species such as ailants. And then, we have planted over 20 thousand street trees and by January 2025 we expect another 6000 trees, in addition to the 628 thousand forest plants that will arrive by the 2025/26 season from the Pnrr. At the Crea nursery (Council for agricultural research and analysis of the agricultural economy), we are growing 100 thousand small trees which will be placed in the city’s parks.”
The strategy of Roma Capitale, according to Alfonsi, it is “the right tree in the right place”: the metropolitan area is enormous and within it you can find very different microclimates. This is why the best solution must be identified. «Together with Crea and with the support of the University of Tuscia, we have developed the Masterplan of Street Trees, which indicates the priority of the interventions to fortify the greenery, but also gives practical indications, for example on the maintenance of the roads where there are trees”.
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