Vegetalisation of walls and streets as tool for urban resilience ? – ECOVILLE

We created a consortium of research laboratories, SMEs and associations involved in the urban approach, able (1) to make an initial assessment of the ecological services provided by these plants, (2) to study their ecological and biochemical functions, (3) to define the implementation technics and (4) urban appraisals, but also to experiment innovative prototypes. The observation and experimentation were carried out mainly on the Greater Paris.
Our program was declined in two main axes:
1- What does exist and how does it work today? This work involved a bibliographic study (synthesis of knowledge on ecological vegetation of walls, courtyards and streets in the city: expected services, implemented techniques, observed social implication ...) but also research on ecological functions (evaluation of biotic functions and abiotic current techniques of vegetation: what biodiversity, what relationship to substrates, conditions and physicochemical constraints ...) and societal contribution (assessment of the societal functioning of vegetation: which governance, which regulation, which perception ...)?
2- which innovative proposals can be made? This involved experimental works at the scale of the building (experimentation of innovative vegetation: reflection on the development of prototypes, substrates ...), but also studies on potentialities at the global scale (evaluation of urban potentialities and expected functioning in an urban renewal project: available areas, types of supports and owners, relationships with green frames, desirable evolution of regulations ...).

We deliver here some examples of results. For more information, see the «Synthèse opérationnelle«.
The analysis of 1,500 tree feet allowed highlighting the particular dispersion of the flora in stepping-stone or in source/sink dispersion from the parks of the district. Sampling of earthworms on a gradient of urbanization allowed to characterize the communities and to examine using molecular tools the effects of distance / isolation between sites: the genetic structure of earthworm populations in Parisian parks seemed to be less influenced by colonization stepping stones processes than by passive transport events, for example by humans. Analyzes showed that trees under water stress could actively regulate their C reserves according to a long-term survival strategy. These results induce the redefinition of current urban irrigation strategies. The silver lime trees planted in the streets, without particular irrigation strategy, could thus be exposed to an increasing risk of mortality linked to water stress.
From a survey of the history of Parisian walls and surveys of inhabitants and managers, an unanimous positive appreciation was given at the beginning of the development of vegetation but when the walls were completely covered, the plants were often removed. The appreciation by city dwellers reversed with the density of greening.
In addition, we have launched experiments on 3 buildings to test a vegetal palette of climbing and falling plants, composed of exotic and indigenous species. Several prototypes were proposed and currently in situ tests are presently running for «green dolphins« and for vertical planting modules.
Finally, a census of the plant walls and series of interviews revealed large territorial disparities according to the urban fabric. The plant walls are more frequent where different built morphologies coexist. The facades on the private spaces received more vegetation than those of the public spaces.

The results have confirmed the interest of the analyzes in urban environment and especially led to new developments of research in the laboratories which should for the most part lead to future innovations. The ECOVILLE program has also been a springboard for research on the urban system.

About fifty academic productions have been produced or are in progress. We mainly worked on a presentation of our results through the construction of an synthesis summary of our research results. This summary will be posted on the websites of the Ministry of Ecological Transition and Plante & Cité. We also value two works: a bibliographic database gathering more than 270 references on green walls (realized by F. Mayrand) and the regulatory context favoring or limiting the installation and maintenance of green walls in Paris, highlighting points of inconsistency (directed by X. Lagurgue).
A national technical day with partial content promoting studies, and field visits of the Ecoville program is scheduled for June 2018. Plant & City Organization.
A national patent was filed (September 20, 2017, Submission 1000422673, ref.B-XLGD0001FR) on a green wall system, the «green dolphin« by XLGD.

Several prototypes are being observed or realized (notably «green dolphin« and «VEGO«). In agreement with the consortium, a «biodiversity tree« project was also initiated with several external partners such as CyBe and Jardin de Babylone.

The promotion of the nature is one of the tools used to improve the urban environment, reduce pollution, mitigate climate changes and contribute to the maintenance of biodiversity. But works in urban ecology have focused essentially on parks, gardens and vegetated roofs. Only few researches involve the greening of walls and streets that could play a social, ecological and physical role, base of an urban sustainability. This research is essential for a global approach to the urban planning and set up of green networks in dense city. We propose a consortium of research laboratories, SMEs and associations involved in urban approach, able to make a first assessment of the ecological services provided by these greenings, to study their ecological and biochemical functions, technical implementations and citizen appreciations, but also to experiment with innovative prototypes.
Our program can be divided into two main areas:
- What is and how does it work today? This work will involve national and international literature review (Phase A on the state of the art and synthesis of knowledge on ecological vegetation walls , courtyards and streets in town: expected technical services, implementations, observed social involvement...) but also active research on the ecological functions (Phase B on the evaluation of biotic and abiotic functions of current vegetation techniques: what biodiversity, what relationship with substrates, conditions and physicochemical constraints...) and social (Phase C on assessment of societal functioning of the vegetation: what economy, what governance, what regulations, what perception and opinions... )
- What innovative proposals can be made? This involves experimental work at building and street scale (Phase D testing of innovative proposals for vegetation: reasoning on the development of prototypes, architectural experiments on coatings, substrates, methods of irrigation...), but also studies on the potential and functioning at a global scale (Phase E on the evaluation of urban potential and functionning expected in an urban project: area available, types of spaces and owners, relationship with greenways, possible regulations...).
The work is set to three years and analyses will be conducted at different scales island / district / city on the city of Nantes and the Grand Paris.