How planetary boundaries can transform urban planning ? A focus on ecological accounting tools for city development.

Abstract

In France, city development is often driven by public land developers. Those are in charge of planning and developing urban projects at a local level, from a few hectares to hundreds, whose global duration may last up to 20 to 30 years, hence linking this urban approach to planning questions.

The current situation is that public developers' economic model lies on the sale of building rights to real estate companies in order to finance unprofitable commons, such as green spaces or public facilities. This links urban design to construction, involving energy, materials and often land artificialization or negative impact on ecosystems. The increasingly stricter legal calls to reduce environmental impacts still struggle to manifest tangible transformations. Thus, urban development still embodies intensive and unsustainable use of natural resources, alongside a lack of consideration for non humans needs.

Following the net-zero climate agenda initiated by the European Commission, new regulations, such as a Net-Zero Artificialization Law (2021) and other texts designed for the reduction of ecosystem disruptions and the de-carbonisation of economic activities are presented as massive game changer for urban planning and urban development. If taken seriously, they destabilise the current business model of public land developers. They actually constitute a complex process for these actors: a clear push to urban reuse/redevelopment, whereas constructed land is obviously far more expensive than natural land.

How can urban development become a tool for ecological transition ? What kind of accounting schemes and practices can be used to move from a mainly financiary perspective to a diversified accounting integrating planetary boundaries ? 

Getting back to the roots of accounting offers a fruitful reading of this challenge. Following Rambaud (2022), accounting schemes rely on 4 main functions: taking into account (accountability as a representing system),counting (with metrics), being accountable and responsible, and accounting (reporting). In line with the field of critical accounting studies, this enables to go beyond the economic field and to tackle environmental subjects, invisible in usual balance sheets.

Drawing from that perspective, we have worked with public land developers to initiate an accounting-based ecological assessment of their projects. In this paper, we explore three experiments and their potential to transform urban planning, in Rennes, Paris and Lille. 

The first experiment considers coloring the current monetary assessment to reflect impact on soil, biodiversity, water, carbon and material. For each usual expenditure, the impact on those categories is evaluated as favorable (green), neutral (grey) or unfavorable (red). At the end of the exercise, expenditures are sorted by impact and category.

The second aims at introducing in the usual economic balance the necessary price to maintain or restore the ecosystems on which our urban lives rely. Inspired by CARE scheme (Comprehensive Accounting in Respect of Ecology), the question is not to give a price to priceless living systems, but to value the cost of maintaining the functionality of an ecosystem, resulting from a collective agreement (Levrel and Missemer, 2019). At the end, items tackling the respect of planetary boundaries are integrated within usual expenses and radically transform the costs of urbanization.

The last is a fully non-monetary assessment based on physical metrics. Inspired by territorial ecology, this approach considers the physical parameters affecting the metabolism of an urban project. Translation into economics parameters comes next.

The paper discusses the transformations these schemes may generate on urban projects and the conditions of replicability of these accounting tools at the level of local authorities.