How can we develop and build in the context of “Zero net artificialisation” ?

5 minutes of reading

23,000 hectares: this is the average annual area of natural, agricultural or forest land reallocated to urbanisation in France over recent years, the equivalent of 2.2 times the area of Paris, 33,000 football pitches or 19 million parking spaces. A figure which makes France one of the worst European students with regard to restraining real-estate development. The impact on biodiversity and CO2 emissions are such that there is an urgent need to hold back this effect. Although the target of Zero net artificialisation (ZAN) was written into the national biodiversity plan in July 2018, the strategy, method and means of bringing this into reality remains to be specified. Likewise the search for a denser, viable and liveable urban development model in large conurbations as well as town centres and small and medium-sized towns.


In 2000, the Solidarity and urban renewal law (SRU) in France marked the first attempts by the French government to limit the space-hungry urban development methodology and triggered the fight against the phenomenon of “urban spread” identified a good twenty years ago. Since then in spite of a beefed-up legislative arsenal[1], it is clear that these provisions have failed, as regularly shown by the unrelenting statistics: more than 20,000 hectares of natural, agricultural or forest land artificialised each year on average, mainly in the production of housing and road infrastructure. And this artificialisation is progressing quicker than the demographic and economic growth. However, numerous causes have been identified: under-use of building stock (vacant dwellings and offices), the affinity of households with individual less-dense housing, price differential of real estate tempting companies to set up on the edges of urban centres, tax framework making “urbanisable” land a source of finance for local authorities, etc.

Urban renewal, densification, reduction of vacant buildings and renaturation of artificialised spaces

Currently, the necessary revolution in practices is becoming more and more imperative as land and societal vulnerabilities caused by these processes are being identified and the consequences of the destabilisation of natural ecosystems is becoming more tangible: collapse of biodiversity, increases in CO2 emissions, soil, water and air pollution, fragmentation of landscapes, water run-off increasing the risks of flooding.

It was against this background that the Zero net artificialisation (ZAN) target was written into the national biodiversity plan in July 2018. This entails limiting as much as possible the “consumption” of new natural, agricultural or forest areas and where this is impossible, to return to nature the equivalent of the areas “consumed” through a compensation process.

Since then, work to inform the Government about the strategy to adopt, the method to use and measures to be applied has gathered pace. Prospective scenarios produced by France Stratégie revealed a necessary reduction of 70% of raw artificialisation and renaturation to 5,500 hectares of artificialised lands per year to reach ZAN by 2030.

If urban renewal, densification, reduction in vacant buildings and renaturation of artificialised spaces left abandoned constitute the main mechanisms to be used, the set of tools available remains to be identified and calibrated: regulatory (planning, density floor in urban development documents), economic (modulation of development tax according to the impact of each operation, increase in land values), diagnostic (artificialisation measurement, knowledge of brownfield sites).

A number of questions are also outstanding and require further detail as suggested by the Assemblée des Communautés de France (AdCF): At what scale (national, regional, local) are the compensation mechanisms applied? How are the artificialised and renatured hectares estimated? How is the ecological and agronomic value of lands taken into account in the land compensation mechanism since “according to the context, a hectare is not equivalent to a hectare”?

Well before these questions are asked, a consensus has not yet even been established on what is meant by “artificialisation”. Do we need to consider all artificialised soils, a category which includes parks and gardens in the same way as a tarmacked car park, or restrict the approach to waterproofed, newly-built or covered soils?

Initial back-zoning in the urban development documents

While these points remain to be clarified and the actors call for the implementation of dedicated governance, some initial changes are appearing in the practices. For a number of months, several commune groups (Hauts de Flandre, Baie du Mont-Saint-Michel) in the approval phase of their intercommunal Local Development Plan (PLU) were faced with hold-ups from Government services, the main reason being the excessive opening up of real estate consumption. On the other hand, the first back-zoning operations are being drawn up, as in the PLU for the Urban Community of Pau Béarn Pyrénées which has reclassified 215 hectares of outlying business parks as natural or agricultural zones and reduced building zones in small villages by 83%.

Against this background where any real estate has now become a precious resource to be used discriminatingly, brownfield areas are major sources of real estate and mechanisms for densification or renaturation. If skills will need to be developed with regard to the renaturation processes and their cost, certain actors already have prior experience on the subject and best practices to pass on. This is the case with the Etablissement Public Foncier (EPF) Nord – Pas-de-Calais, which has “transformed more than 2,000 hectares of mining real estate into wetlands, dry grasslands, reed beds and forests, etc. to constitute the green infrastructure of the mining basin”, explained Guillaume Lemoine, biodiversity and ecological engineering specialist when questioned by the Le blog du foncier. A precursor, the EPF does not intend to stop there and is thinking about ways of keeping soils and green spaces in place during demolition works, conceiving temporary uses for its stock of real-estate (biodiversity, biomasse, land-art, urban allotments) and positioning itself as a real-estate compensation facilitator by proposing renatured or to-be-renatured real-estate when responding to compensation requirements for projects located nearby.

A new urban development model

Besides the development of a “brownfield economy”, the ZAN target should contribute to the emergence of denser, viable and liveable urban development model in large conurbations as well as town centres and small and medium-sized towns. Reconciling increasing needs for dwellings to accompany the demographic evolution and structure of households and scarcity of real estate assumes the conception of new real-estate products and other ways of building: building over, more compact urban and architectural forms, dwellings closer to living spaces and town centres. But to be understood and talked about, this density and compactness must leave room for manoeuvre for the population and give a place of honour back to nature. This involves writing new participatory urban narratives and increasing positive biodiversity projects by integrating urban agricultural production. In other words, achieve a decrease in the consumption of spaces, resources and energies preserving society in the process.


[1] The law for access to housing and renewed urban development (Alur) of March 2014 reinforces the principle of an “economic use of spaces”