In Paris, greening is gaining ground despite some persistent obstacles

In Paris, greening is gaining ground despite some persistent obstacles
In Paris, greening is gaining ground despite some persistent obstacles

To combat heat islands, greening buildings and public spaces appears to be a relevant solution. In Paris, more and more roofs and facades are becoming greener. If several obstacles persist, this is not enough to dampen the enthusiasm of the capital, which has just launched its 2025-2030 Biodiversity Plan.

For many years now, temperature records have been broken every year across the globe. The planet is warming at high speed because of human activity, and many countries are working to find solutions to reduce the temperature in large cities in particular, which are more prone to extreme heat.

To try to curb this rise in temperatures, several solutions are available to public authorities. The greening of buildings and public spaces is part of this. The city of Paris understands this well, and it is in this sense that it has adopted a Biodiversity Plan since 2011, then again in 2018, supposed to strengthen the place of nature in the city. The capital has just launched the sequel, with its 2025-2030 Biodiversity Plan.

The climatic virtues of plants on buildings

As Yann-Fanch Vauleon, landscaper at Apur (Parisian urban planning workshop), explains, more criteria will be taken into account in this new Biodiversity Plan: “ the first Plan was really based on the green and blue frames. In other words, actions aimed at preserving terrestrial, aerial and aquatic fauna and flora. For this new plan, we will be more interested in the black frame, therefore in light pollution, in the brown frame, that is to say in the continuity of the floors, and in the white frame, everything that affects to noise pollution “.

Despite these changes, This does not mean that revegetation will be neglected by this new Plan.. Vegetation actually presents a major asset in the fight against heat islandsand this, for several reasons, as Mr. Vauleon explains: “ Vegetation creates shade, so it prevents surfaces from heating up. Then there is the fact that the plant does not store heat, so it does not redistribute it at night. And finally, there is plant evapotranspiration. This process, which is part of photosynthesis, will put water back into suspension in the air, which will cause the ambient temperature to drop. “. So many attributes that make the greening of buildings and public spaces essential to bring down the mercury.

In the Local Urban Plan (PLU) of the city of Paris, it is also recommended to plant trees in front of the facade of a building, on the southern slope. The shade will thus limit the rise in temperatures on the building.

Several obstacles persist, despite a growing trend towards revegetation

The greening of the facades of a building is also relevant for the insulating aspect of the plants, as the Apur landscaper points out: “ The plants will reduce the radiation of the sun on the facade, which will protect the facade from this heat “. Small downside however, this solution is not included in the insulation calculations. “ Vegetation is not something very standardized. We do not know how to make calculations that could be taken into account by engineers », Regrets Yann-Fanch Vauleon.

Climbing plants are the most popular for greening facades. In Paris, the vast majority of these are found in the interior courtyards of the capital’s buildings. But this process is still struggling to develop, in particular due to the failure to take plants into account in insulation calculations. In 2016, Apur counted around 30 hectares of green walls in Paris.

Another obstacle to the development of greening in the capital: the nature of Parisian roofs. Many roofs in Paris are not flat, which poses a problem for urban agriculture, for example, which is an integral part of the city’s greening process.

Guides for thoughtful greening of buildings

There’s no reason to be discouraged, however, since there is a real trend towards urban agriculture and the greening of the capital. Proof of this is that Apur is currently looking for 300 hectares to revegetate in the capital. For the moment, it is mainly the buildings belonging to the city which are the most green.such as public facilities or even schools.

There are also specific rules to follow for the greening of buildings in the capital. Paris has two guides for this. A guide for the greening of roofs and one for that of facades. These guides notably recommend various ways of planting, what types of substrate to choose, at what depth to plant the plants, or even which species to favor depending on the sunlight available or the plant’s water needs.

So things are going at their own pace, but there is indeed a real trend towards greening. More and more roofs are being greened, but this dynamic results more from the work of the city of Paris with its partners than from the PLU, as Mr. Vauleon explains: “ It is mainly social landlords or large institutions like BNP Paribas who have greened their roofs. All these partners of the city of Paris are signatories of the 100 hectares charter, which is a document dating from a little less than 10 years ago and which was put in place to strengthen the greening of buildings in the city “.

A Biodiversity Plan planned, but not yet fleshed out

As for the Paris Biodiversity Plan for 2025-2030, “ it’s still a little early to know what we can expect from him », underlines Yann-Fanch Vauleon. For the moment, there have been several public consultations with contributions, “ and there, the city of Paris is in the process of holding various workshops on all these themes, in collaboration with associations like France Nature Environnement for example, to try to strengthen this plan, improve the indicators that will be there, so as to be able to vote for larger budgets for the next plan », explains the landscaper.

Before this plan comes into force, and without knowing what it will actually entail, the short-term mission is to continue to raise awareness of biodiversity, without forgetting anyone, as Mr. Vauleon explains: “ We must continue to raise awareness on a large scale. Even city officials, who do not all have the same level of sensitivity. We must continue to train, and for that we need more budget “.

We will have to wait a little longer before having a precise idea of ​​what exactly the future Biodiversity Plan will consist of. “ We will first have to go around all the institutions, so that everyone can give their ideas. After which there will be a lot of synthesis work to do. This will be done in December so there is still a way to go for that », concludes Mr. Vauleon.

Jeremy Leduc

Photo of one: Adobe Stock

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