FFrom Madrid to Berlin and Paris to Budapest, scientists and planners agree that trees, trees, and more trees can help make Europe’s cities more comfortable — and even survivable — over the coming years, as global warming strengthens its grip.
But concrete sidewalks, tall buildings, historic plazas, and underground parking lots are a hostile environment for the trees, and authorities are finding it difficult to plant more. In fact, many EU cities are less green than they were a century ago.
“It is an enormous challenge,” said Christophe Najdowsky, vice-mayor for revegetation and green spaces at the Paris City Council. “We know that with enough trees we can lower the summer temperature in the city by up to 8 degrees Celsius. They are basically natural air conditioners. But planting them is not always easy.”
The latest report from the Intergovernmental Panel on Climate Change couldn’t be clearer: Trees in cities combat climate change directly, by storing carbon, and indirectly, by cooling urban areas down – reducing energy demand.
They also provide city dwellers what the report calls “multiple co-benefits”: improved air quality, reduced heat stress, fewer “urban heat islands” caused by streets and buildings that absorb and retain heat, and “improved mental and physical health.”
For city halls, in short, planting more trees shouldn’t be a no-brainer. But according to the Organization for Economic Co-operation and Development, tree numbers in many European cities have been declining since the early 1990s, with some large communities losing up to 10% of their cover.
Experts say this is partly because older trees from the late 19th and early 20th centuries—those that survived successive generations of urban planners’ efforts to make more room for cars—are starting to reach the end of their lives.
But also because of the technical difficulties, and the cost, of growing new trees. According to Ana Luisa Soares, a landscape architect at the University of Lisbon, the new tree could cost the city administration up to €2,000 (£1,740) over five years.
“You need to buy the tree,” Soares said. You have to plant it and water it—especially in the first five years, when it’s most vulnerable. Life is hard for a tree in a city: compressed soil, polluted air… You have to maintain it, prune it, and treat it for disease. When you’re talking about tens of thousands of trees, that’s a huge investment.”
The advantages, for city-dwellers, seem obvious. “We need trees,” she said. “They matter to all of us, residents and visitors. They give us more shade, better air quality, lower temperatures and natural beauty – basically, more trees mean happier people. We know this. And they will be more vibrant in the future.”
But while the costs are easily quantifiable, the benefits are less so. Even worse, Soares said, the environmental, social, economic, aesthetic and health benefits that trees provide are “often simply ignored, because cities are simply looking at managing costs.”
In an attempt to put a monetary value on the benefits of trees, Soares adapted an American software program, iTrees, and infused it with data from 41,000 exotic trees in Lisbon. It found that while the trees cost about $1.9 million annually, the services they provided were worth $8.4 million.
“So for every $1 the city invests in its trees,” she said, residents get about $4.5 in benefits: an energy saving of about $6.20 per tree, a carbon reduction of $0.33, air pollution removal of $5.40, and a $47.80 reduction in storm water runoff. . It has also been found that trees add significantly to property values.
The European Commission last year proposed draft regulation that would require the bloc’s 27 member states to ensure that at least 10% of the area of all cities, towns and suburbs will be planted with trees by 2050, and commit to no loss of green space.
But cost is not the only hurdle facing city planners. Often, said Nejdovsky of the Socialist-Green city council in Paris — which over the past two years has embarked on one of the most ambitious tree-planting programs in Europe — cities simply can’t afford to plant trees where they want.
“The biggest problem is the underground infrastructure. The metro, the gas pipes, the electricity and telephone cables, the car parks…you need a certain depth of soil under the tree. We would like to plant along the avenue de Rivoli, which crosses the city center from east to west, but unfortunately The metro is located right below it.
Elsewhere, ensuring emergency vehicle access along narrow streets can be an obstacle, and heritage laws can prevent trees from being planted on or near buildings, streets, and squares for which they were not designed. Most of the large squares in Europe’s cities are designed as open spaces with great views.
“This is the case in Paris, for example, the Place de la Concorde or the Avenue de la Opera,” said Najdovsky. “The city’s architects argue that they must remain as they were initially designed, unadorned with trees, and that the view of the Opéra Garnier cannot be obscured or spoiled. We are looking to make concessions, but they are not direct.”
In other major arteries such as the Rue de Wagram, however, Paris is busy replanting trees uprooted by their tens of thousands during the 20th century as the city has transformed grand boulevards, lined with double rows of trees, into four lanes with roadside parking. .
“Basically,” said Najdovsky, “we aim to drastically reduce the space for cars in Paris, and use as much of it as possible to plant trees: a massive re-vegetation program, to re-conquer nature above the car. The goal is to plant trees in large numbers and where possible.”
Since its re-election in 2020, the council has planted 38,500 new trees in the capital, including 18,000 on the banks of peripherique Ringroad, 12,000 in the Bois de Boulogne and de Vincennes, and 8,000 in the streets and squares of the city centre.
It aims to plant another 21,000 this winter, including 11,000 around Ring Road and 800 on 80 other streets in the city centre. The city also plans three “urban forests” mainly in the east of the city, including one on 3.5 hectares (8.65 acres) of former railway siding in the 20th arrondissement that will feature 2,000 new trees by 2024.
Its ultimate goal, by the end of its six-year term, is 170,000 new trees, including 200,000 on inner-city streets. Paris will be mostly dominated by traditional plane trees, but some Mediterranean species are also being introduced – such as the holm oak, which is more resistant to warmer temperatures.
As happened in Brussels, where the term is 10 years plan canopy (or Umbrella Plan) Aiming to preserve the city’s existing trees and plant several hundred new ones each year until 2030, the Paris city council’s plans have drawn heated protests at times, most notably from motorists’ organizations.
“As I said, it’s not always easy, and objections from motorists and residents are just one of the many problems we face,” said Nejdovsky. He said, “Some residents say to me, ‘Look, I don’t want trees outside my apartment—they’re going to cut the light, and that’s going to cut thousands off the asking price.'”
“I tell them: When summers in Paris regularly start to get 40°C or 50°C, then what do you think your apartment is worth? If the city is basically unlivable, who has more to lose?”