(Re-)balancing urban areas and nature: conclusions from a year of reflection guided by the Palladio Institute

In the face of increasing urbanisation around the world, climate change and declining biodiversity, the question of the relationship between urban areas and nature is becoming ever more pressing. Over half the world’s population now lives in an urban area, and this rate is even higher in developed countries (80% in France). This urban growth has been synonymous with widespread land take and soil sealing, with nature driven back to dedicated zones or areas not often frequented by humans. Today, an about-turn is under way in our approach to nature, the ecosystem services it provides, and our desire as humans to have access to it.

Balancing or reconciling urban areas and nature was the theme of reflection for 2023 selected by the Palladio Foundation, a French institution dedicated to building the urban areas of tomorrow. The foundation’s auditor, Jean-Sébastian Milesi, an expert in residential buildings and mixed-use projects at Artelia, gives us an account of the rich discussions that took place.

What is the Palladio Foundation?

It was founded 15 years ago and and brings actors in urban development together to focus on the changes taking place in towns and cities and the associated social and environmental issues. The Foundation encompasses several areas of activity, including the Palladio Institute, which each year chooses a theme, selects approximately 30 people from a wide variety of backgrounds (developers, architects, bankers, insurance companies, engineers, etc.) and organises conferences attended by an equally diverse range of participants (sociologists, demographers, urban planners, economists, researchers in various fields such as biodiversity, etc.). This year the theme was “(Re-)balancing urban areas and nature”.

How is this theme of the relationship between urban areas and nature being approached today?

It’s a complex subject and is all the more relevant for us to discuss given the current context of economic tension (a crisis in the property sector and increasing public debt in many countries). On the one hand, our vision of urban areas and the built environment is changing. We are moving away from a highly functional approach and towards consideration of climate and biodiversity issues, factoring in water resources, soil permeability, and requirements relating to vegetation cover and species conservation. On the other hand, there is a financial constraint, because the cost of land is very high in urban areas. This raises the question of economic optimisation of non-built environments, their management, and also governance between public and private spaces. If you want to create green corridors, for example, private gardens must be integrated into them, because they often represent a very large proportion of urban green spaces.

What types of topics were discussed?

The conferences and participants’ presentations covered a huge variety of discussions and questions. How should land be reserved for “nature in the city”? Should this nature be distributed everywhere by increasing vegetation on roofs and patios? How must water management, which is indissociable from vegetation, be transformed? Which nature categories meet which requirements? A meadow can capture rainfall and maintain a certain biodiversity, but this is not the best solution for reducing heat islands. To do this, trees are required that will provide shade in public spaces whilst leaving free space underneath their canopy. The choice of the plants themselves is also a topic of debate. How are native species going to adapt to continuing climate change? Should they be replaced immediately with non-native species that grow in hotter climates? Reintroducing agricultural production in urban environments is another aspect of this topic. Several possibilities are being considered, such as automated vertical farms, rooftop vegetable plots, and changes of use for some urban blocks (wasteland, car parking, etc.). Reconciling urban areas and nature involves reconsidering all these aspects.

Is reducing the heat island effect becoming a key focus for local authorities?

Yes. With climate change, cities are becoming unbearable in the summer, because until now they have been designed using primarily stone-based materials. They have been developed from a standpoint of opposition to nature. Reducing stone-based materials and adding vegetation, in particular by replanting trees, is one lever for reducing summer temperatures in cities. Vegetation of roofs and patios is another way to improve living comfort in the summer, aside from the role it plays in capturing rainfall.

And what about urban sprawl and land take?

In France, just like in the United States, the single-family housing model is very widespread. Many people aspire to live in a detached house surrounded by grass, flowers, and trees. Since the Covid-19 pandemic, many city-dwellers have been wondering about going to live in the countryside and working remotely. Cities that are not pleasant to live in accentuate urban sprawl and land take, driving agricultural activities further and further away and aggravating transport issues. Reintroducing more nature into cities is a way of stopping this vicious circle. It is important to make cities more pleasant places to live in, and for them to meet citizens’ needs for contact with nature.

Setting plants aside, what role are animals expected to play in this urban nature?

Our perception of nature is changing. Leaving behind the idea of controlling nature for aesthetic reasons, we are moving towards a less constrictive approach, allowing nature to “do its thing”. For example, this means letting grass grow in certain areas, allowing “wilder” hedges to develop, creating green or blue corridors (around rivers) within which animals can move around freely. However, nature in this freer form, less constrained by humans, has yet to be fully accepted. On the face of it, most of the population is in favour of nature in urban areas and the presence of animals. However, if you start saying there will be more insects or that children will come home a little more muddy because the tarmac has been removed from the playground… then some people’s enthusiasm cools off rapidly.

How is urban nature taken into account today in your profession as an engineer at Artelia?

For my colleagues, specialists in urban development, urban nature has become a standard topic, both in the context of strategic assistance for local authorities and during design studies for development project. Combating heat islands, reducing land take and soil sealing, and managing water more naturally are the reality in the European countries with the highest levels of urbanisation, even though urban nature initiatives are obviously subject to financial decisions. In my own work, focusing on mixed-use buildings and projects, the way I work has changed. From the preliminary study phase, eco-design is integrated into the projects. We look at how the density of the built environment can be better managed to leave areas of exposed earth at ground level, thereby facilitating rainwater infiltration and plant growth. This is also very interesting from a technical point of view. In a green roof for example, the soil depth must correspond to the plants used, the plants themselves must be chosen carefully, the loads on the structure must be calculated, a different approach to water management is required… Artelia’s strength lies in drawing together, in-house, the full range of specialisations and expertise required for this type of project, including ecologists.

Do you have examples of flagship projects showcasing these changes?

As a good example, we have recently been working on a real estate complex which will be occupied by a branch of the University of Chicago in Paris. This building has been built over the rail network at Austerlitz station, on a concrete slab, with vegetation at the centre of the block in earth up to 2 m in depth. A great deal of though was put into promoting biodiversity and the species that can live in this space in relation with the pre-existing green corridor. This is a great example of a completely hard-surfaced plot on which we have re-created nature.

We also have the Arboretum project in Nanterre La Défense, an exemplary sustainable campus baptised the “forest city”, for which Artelia provided design services. The buildings have been constructed in 9 ha of parks, gardens and vegetable plots. Nearly 1000 trees and bushes were planted on that occasion. We have also participated in creating the Olympic athletes’ village in Saint-Denis, in which the theme of urban nature also played a remarkable role. The Palladio Foundation held a discussion on this project, and the video is available on the internet. The Group is involved in many other flagship operations in France, such as the Grand parc Garonne in Toulouse, or the Bastide Niel project in Bordeaux, but also in Denmark where integration of nature into urban areas and buildings has reached a very advanced level.

Does the Palladio Foundation plan to publish a summary of the various reflections of 2023?

Yes, a summary has been published in the “Actes de l’Institut Palladio” collection. This reflection about nature and urban areas has been a highly enriching experience that helps to identify future directions and further changes. For me, one of the very positive points is that through nature we can recreate a connection between the public space and the built environment. This is very important in terms of today’s city lifestyle.

More information can be found in the “Actes de l’Institut Palladio” publication (Re-)balancing urban areas with naturehttps://fondationpalladio.fr/nos-publications/