PARIS — Long a favorite spot for picnics and sunbathing, the lawns surrounding the Eiffel Tower have recently become the scene of furious protests. First came a social media campaign. Then a rally by dozens of local residents. Before long, a protester had hunkered down in a nearby plane tree for a hunger strike.
The source of their anger? A plan to cut down more than 20 trees, some over 100 years old, around the tower as part of an effort to build a huge garden and ease tourist congestion.
The controversy is just the latest in a series that has engulfed Paris City Hall as it tries to green the city, a task that appears all the more urgent as scorching temperatures bear down on the French capital, and on the rest of Europe.
Trees are considered some of the best defenses against the radiation that contributes to the heat waves that are on the rise everywhere because of global warming. They provide much-needed coolness in dense cities like Paris, where temperatures were in the high 90s in the afternoon Monday and expected to go higher.
“Without the trees, the city is an unbearable furnace,” said Tangui Le Dantec, an urban planner and co-founder of Aux Arbres Citoyens, a group protesting the felling of trees in Paris.
In recent months, small protests have sprouted across Paris, with residents and activists rallying around trees condemned by the sprawling urban development projects that have at times turned the capital into a giant construction site.
In April, they filmed the felling of 76 plane trees, most of them decades old, at the Porte de Montreuil on Paris’s northern outskirts. City Hall wants to turn the site into a huge square, part of a project by the mayor, Anne Hidalgo, to create “a green belt” around the capital.
“Ms. Hidalgo please stop the massacre,” said Thomas Brail, the founder of the National Group for the Surveillance of Trees, as machines chopped up trees behind him, in a video he shot in April. Mr. Brail later staged an 11-day hunger strike in the plane tree near the Eiffel Tower.
Yves Contassot, a former deputy mayor of Paris in charge of the environment and a member of the Green party, said cutting down trees had become “a very sensitive question that causes a bit of a scandal at a time when we talk about fighting global warming in big cities.”
At first, the plan to redevelop the traffic-clogged area around the Eiffel Tower seemed environmentally sound to Paris residents. Most vehicles would be banned, and a network of pedestrian paths, cycle lanes and a parks would be created.
“A new green lung,” the City Hall boasted on its website.
But residents discovered in May that the plan also meant cutting down 22 well-established trees and threatening the root system of several others, including a 200-year-old plane tree planted long before the Eiffel Tower was built in the late 1880s.
“The poor tree was planted in 1814, and one morning some guys want to make room for luggage storage and it gets swept away,” said Mr. Brail, the protester who held a hunger strike in the tree, mocking the plans to improve facilities for visitors.
A series of protests, as well as an online petition that gathered more than 140,000 signatures, eventually forced the City Council on May 2 to change its plans and promise not to cut a single tree as part of the greening project.
Emmanuel Grégoire, Paris’s deputy mayor in charge of urban planning and the architecture, said in an interview that the city realized it was “losing a symbolical battle over the project’s green ambitions.”
In 2007, Paris adopted a climate plan that helped reduce the city’s carbon footprint by 20 percent from 2004 to 2018, and almost doubled the consumption of renewable energy, according to a recent report by regional authorities. Paris’s new goal is to become a carbon-neutral city powered only by renewable energy by 2050.
Mr. Le Dantec, the urban planner, acknowledged that “regarding pollution reduction, there has undoubtedly been an improvement.” He referred to Ms. Hidalgo’s successful, though contested, plans to limit car use in the capital.
But he added that Paris’s urban plans had neglected another reality of climate change: rising temperatures, against which trees are considered some of the best defenses.
Trees cool cities down by providing shade and mitigating the effects of so-called “urban heat islands,” which are prevalent in Paris, by absorbing radiation. Météo France, the national weather service, has estimated that temperatures on those heat islands during recent heat waves were sometimes 9 to 18 degrees Fahrenheit warmer than in surrounding areas.
In mid-June, as France was suffocating under scorching temperatures, Mr. Le Dantec wandered around Paris with a thermometer. In the Place de la République, he recorded temperatures of up to 140 degrees Fahrenheit on concrete surfaces, compared with 82 degrees under a 100-year-old plane tree.
“Our best protection against heat waves are trees,” said Dominique Dupré-Henry, a former architect at the environment ministry and co-founder of Aux Arbres Citoyens.
But of 30 big cities studied by the Massachusetts Institute of Technology, Paris has the lowest tree cover, with about 9 percent, compared with compared with 12.7 percent in London and 28.8 percent in Oslo.
“This is exactly the opposite of adapting to climate change,” Ms. Dupré-Henry said.
Mr. Grégoire said Paris planned to plant 170,000 new trees by 2026. Taking the example of the Porte de Montreuil, the area in the north of Paris, he said far more trees would be planted than cut down.
“It’s a project with very high environmental standards,” Mr. Grégoire said, emphasizing the transformation of what is now a huge asphalt roundabout into a green square. “The outcome is positive in terms of fighting urban heat islands.”
Regional environmental authorities are less confident. In their assessment of the project, they noted that the building work and new infrastructures “will, on the contrary, add more heat.”
Mr. Le Dantec also said that, in the short term, young trees are less effective than older ones in mitigating global warming, because their foliage is smaller and cannot absorb as much radiation. “A 100-year-old tree is worth 125 newly planted trees” in terms of absorbing carbon dioxide and cooling down its surroundings, he said.
At the Porte de Montreuil, residents had mixed feelings about the project. Lo Richert Lebon, a 57-year-old designer, praised the “green efforts,” saying they would help improve the quality of life in this long-decaying suburb.
But “lawns are not worth trees,” she added, standing in the shade of plane trees scheduled to be felled, as part of the redesign of a flea market in the area. “Trees should be integrated in these efforts, rather than being an adjustment variable.”