Faced with environmental degradation on an unprecedented global scale, soils are emerging as a focus of scientific, public and political concern. Described as ‘the Earth’s living skin’, they are valued for their many contributions to the functioning of terrestrial ecosystems and human societies. In France, the ‘Climate and Resilience’ Act (2021) recognises these ecological functions, but this conception contrasts with the view of land as a fragmented and exploitable surface promoted by the land tenure system. To shed light on this tension within the social institution of land, this thesis examines the integration of land values into French land governance. Adopting an ecological socio-economic perspective, it explores how these values are reconciled within the legal standards, economic models and social practices that shape spatial planning.

Part One presents the scientific and theoretical approach of the thesis, which combines three elements: the framework of institutional resource regimes, the analytical model of property as a ‘bundle of rights’, and a pluralist approach to the values of nature and land. Land governance thus emerges as a process of negotiating institutional regimes and arrangements that shape the use and appropriation of land. Part Two examines these negotiations in three contrasting territorial contexts: land initiatives to support pastoralism at the UNESCO site of the Causses and Cévennes (Chapter 4), the establishment of two national nature reserves in the Hérault (Chapter 5), and an urban planning dispute in Besançon (Chapter 6). Part Three analyses the macro-institutional transformations brought about by the ‘Climate and Resilience’ Act and its objective of zero net land take (ZAN). The ZAN scheme is examined as a land-take quota trading system (Chapter 7), whilst Chapter 8 studies the emergence of an economic sector dedicated to land renaturation.

From a theoretical and methodological perspective, this thesis highlights the value of an interdisciplinary and pluralist approach to the relationship between land and society. The concept of a ‘regime of valorisation’ operationalises this vision by linking the analysis of processes of valorisation and appropriation, whilst the ‘matrix of rights bundles’ sheds light on the construction of land tenure arrangements and the territorialisation of regimes of valorisation. Empirically, the study shows that land has always been a discreet actor in the transformations of land governance. Established in the 18th century on the basis of an absolute, exclusive and individual conception of property, the French land tenure system has gradually incorporated collective values associated, often implicitly, with the functions of land. In the areas studied, this stratification gives rise to conflicts and negotiations between heterogeneous values. They sometimes result in territorial compromises that redefine relationships of ownership through a process of communalisation, characterised by the inclusion of a greater diversity of stakeholders in the use, decision-making or political control of land. Land thus emerges as a hybrid asset: both a vehicle for private rights and the hub of a network of collective interests, giving rise to pluralistic governance. In this context, the current focus on soil health (or quality) helps to clarify the pedological dimension of land relations and opens up the prospect of governing land as a common good. This could be based on a relational conception of land ownership: no longer an exclusive right to the land, but a set of interdependent relationships operating at different levels and involving shared responsibilities.

Members of the jury

• Franck-Dominique Vivien, Professor, University of Reims (Chair)
• Hélène Rey-Valette, Senior Lecturer, University of Montpellier (Rapporteur)
• Jean-David Gerber, Associate Professor, University of Bern (Rapporteur)
• Nathalie Blanc, Research Director, CNRS (Examiner)
• Maylis Desrousseaux, Senior Lecturer, Paris School of Urban Planning (Examiner)
• Olivier Coutard, Research Director, CNRS (Co-supervisor)
• Harold Levrel, Professor, National Museum of Natural History (Co-supervisor)
• Philippe Billet, Professor, University of Lyon 3 (Co-supervisor)

This PhD thesis examines the various political dimensions of the spatial marginalisation of precarious housing arrangements for exiled people (camps, squats, third places). It is based on the hypothesis that, by geographically distancing these informal spaces from city centres and citizens’ daily movements, public authorities discourage local engagement. Whilst some supporters withdraw in the face of difficulties, others – though fewer in number – nevertheless manage to sustain their commitment. How can we raise awareness of a cause that has become ‘invisible’? How can one sustain a commitment in areas of spatial and social marginalisation? This project aims to analyse the dual social and spatial dimensions of engagement, by bringing together local contexts (geographical and political), the characteristics of engagement structures, and the individual trajectories of volunteers. It draws on multi-sited field research conducted in Paris, on the French-British border (Calais) and the French-Italian border (Briançon). By combining qualitative and quantitative methods, it seeks to understand the processes through which the socio-spatial conditions of engagement with exiled people evolve.

Barracks, ports, hospitals, prisons and railway sites are the focus of numerous regeneration projects in European cities. A substantial proportion of urban regeneration therefore takes place on ‘state-owned land’. This thesis helps to explain these urban restructuring processes, which also contribute to the reconfiguration of the state in its physical dimension. It examines the reasons behind and the ways in which the presence of a particular type of national operator – railway companies – is being reorganised within the urban environment. The comparative study, conducted across two countries (Italy and France) and four cities (Milan, Bolzano, Paris and Nantes), identifies two main explanatory factors. On the one hand, since the 1970s, city authorities have been challenging the ways in which the railway network occupies urban space, against the backdrop of their increasing involvement in urban planning. Furthermore, real estate strategies and expertise have been developing within public transport firms since the early 1990s, against a backdrop of greater financial autonomy and increased financial pressures. The reorganisation of this sector’s logistical capacity (the ability to organise the flow of goods and people) in cities can therefore be explained by the alignment of the three dominant ‘approaches’ to the reasons for the redevelopment of railway sites, namely: property, urban planning and industrial. This alignment takes place within development projects and is implemented differently in Italy and France. In Italy, the more flexible institutional framework governing the transfer of railway land gives rise to varied agreements between operators and local authorities depending on the city, in contrast to the French case, where processes and outcomes are more consistent from one city to another. Compared with existing approaches to the relationship between cities and the state, the dual shift proposed in this thesis – towards operators and towards the material dimension of the state – sheds light on new relationships between the reorganisation of the state and urban restructuring.

Over the past few decades, the range of electricity services available on the African continent has diversified considerably, notably through so-called decentralised solutions (solar lamps, domestic solar kits, mini-grids) (Guillou, 2022; Cholez & Trompette, 2022). These solutions are set to play a central role in providing access to electricity, particularly in rural areas (IEA, 2023). However, even as increasing levels of investment are being channelled into the development of renewable energy, a significant proportion of solar projects in sub-Saharan Africa – particularly mini-grids – end in failure, with equipment deteriorating and struggling to remain operational for more than ten years (Etienne, 2022; Cholez & Trompette, 2019; ENEA & Practical Action, 2023). Investors, including mini-grid developers and operators, as well as suppliers of domestic solar kits, face numerous challenges in ensuring the long-term viability of decentralised electricity infrastructure. The lack of data and knowledge is thus a major obstacle to the productive use of electricity generated by mini-grids, even though such uses are a key condition for their profitability (ESMAP, 2022; UNIDO, 2022). The organisation of stable maintenance and repair supply chains is another such challenge. Building on these observations, this thesis examines decentralised electricity infrastructure in sub-Saharan Africa and the obstacles to its sustainability, approaching the subject through the lens of solar workers and their activities. The aim is to suggest that the sustainability of decentralised electricity infrastructure fundamentally depends on the existence of ecosystems of workers or professionals, rooted in specific local areas. This leads to an analysis of the conditions under which such localised professional ecosystems emerge, which are capable of adapting this infrastructure to local contexts over the long term. Two contrasting case studies in relation to this issue were selected for the fieldwork: Cameroon, where 26 per cent of the rural population has access to electricity, and Madagascar, where less than 15 per cent has access (World Bank, 2023). What local maintenance and repair skills are required to ensure the long-term viability of a decentralised electrical infrastructure? What conditions are needed to support, or even encourage, the emergence and development of such skills into an ecosystem of specialist stakeholders? This thesis posits that we must examine these skills by situating them within their regional professional ecosystems in order to understand the diversity of stakeholders, the complexity of the relationships between them, and the vitality of local maintenance economies. The approach we propose here will enable us to focus on a wide variety of workers beyond engineers alone, including professionals of all qualification levels and from all sectors. It builds on sociological approaches which, in recent years, have encouraged a focus on the often-overlooked work of those referred to as ‘unskilled labourers’, who nevertheless form part of the ecosystem of stakeholders ensuring the technical management of infrastructure. As part of the proposed thesis, repair technicians and tradespeople will therefore form part of the specific groups under study. Through an analysis of work ‘in the making ’ (Ughetto, 2018), the aim will be to explore the role they play in the operation and sustainability of decentralised electrical infrastructure, particularly through the numerous ‘tinkering’ and innovations that ensure the day-to-day functioning of electrical infrastructure in a context of unreliable service provision by conventional networks (Rateau, 2022; Olivier de Sardan, 2023).

This PhD project aims to explore in greater depth the relationship between equity and ecology in the field of water management, an approach that is now essential for sustainable management in the context of global change. Our main hypothesis is that the sustainability of water resources in the Adour-Garonne basin (BAG), which has been facing a crisis for several years, is interdependent on the capacity of water governance models to take account of situations of vulnerability – both human and non-human – within their management area; whilst always upholding the principles of solidarity between upstream and downstream areas, and between surface water and groundwater. We will seek to identify equity issues that could enhance sustainable water management in a context of uncertainties linked to global change. We will also examine the ways in which water governance models, depending on the context (hydrology, stakeholders, scales, uses, mechanisms), are adapted and implemented across the territory, and how they can sometimes serve as a means of resolving other issues that fall within the public interest.

Chemnitz, which was Germany’s European Capital of Culture (ECOC) in 2025, is Saxony’s third-largest city. Although little known outside Germany, Chemnitz nevertheless made the front page of The New York Times in August 2018 following several consecutive days of far-right riots.

This development led the team in charge of the ECOC bid to highlight the significance of the presence of neo-Nazi groups in the city. Whilst this is nothing new in the city, the 2018 riots served to bring the violence of the far right in Chemnitz into sharp focus. The second bid booklet, published that same year, therefore made the fight against the far right and the promotion of democratic values the central theme around which the cultural events of 2025 would be organised. However, the national and local elections in June and September 2024 resulted in the far-right AfD party gaining political dominance both in Saxony and on the city council. Moreover, elected representatives from the Pro-Chemnitz and Freie Sachsen groups – who had openly participated in organising the 2018 riots and who oppose the values championed by the ECOC – (once again) secured seats on the City Council in 2024.

My doctoral research therefore examines the interplay between far-right parties and public cultural policy. I am analysing the positions of various political parties regarding the European Capital of Culture (ECOC), as well as changes in budgets and regulatory frameworks relating to the cultural sector and their impact on the activities of artists and organisations in Chemnitz. The aim of the project is to gain a deeper understanding of the cultural policy programmes of emerging far-right parties in Germany, such as Freie Sachsen and the AfD.

Urban planning has undergone significant changes in Europe in recent years. In France in particular, these have resulted in a strengthening of town planning documents, making them a key focus of local public policy. The Local Urban Development Plan (PLU), often inter-municipal (PLUi), serves as the reference document for the granting of planning permissions (building, development or demolition permits, and prior declarations), and therefore for the majority of projects carried out in towns and cities. Whilst the ‘Zero Net Land Take’ (ZAN) objective, aimed at reducing land consumption, represents one of the major shifts in planning and thus in the evolution of urban development in response to climate challenges, it is not the only one. Indeed, town planning documents are increasingly incorporating provisions aimed at mitigating climate change, adapting to its effects and limiting the loss of biodiversity (Chavez Colmenares 2024). This development is part of a broader trend towards the ‘greening’ of urban planning. At the same time, the changing role of the PLU(i) reflects the logic of ‘project-based urban planning’ (Demouveaux and Lebreton 2017), which involves, in particular, defining a territorial development strategy, but also evolving the relationship with private sector stakeholders, who are essential links in territorial policies. In the face of reduced resources for public bodies and rising land and property costs, the urban planning document serves as a tool to steer these bodies’ projects towards the objectives set by local authorities, thereby enabling public action at a lower cost. However, more environmentally friendly urban planning comes up against deeply ingrained, even routine, perceptions and practices regarding the creation of space. Indeed, much research highlights the complexity involved in changing the practices that greening entails. They highlight the challenge posed to stakeholder networks, standards, economic models and, more generally, established ways of working, for which the integration of ecological considerations leads to difficulties or even conflicts. These can hinder the implementation of certain projects by stakeholders with limited resources or those seeking to maximise the economic profitability of their operations. Building on these observations, this thesis aims to understand how the various stakeholders involved with the regulations set out in town planning documents (various local authority departments, elected representatives, private individuals, property developers and designers) incorporate these regulations into their work, the ways in which they impact projects, and how these regulations serve as a basis for dialogue and negotiation between the stakeholders, particularly with regard to the granting of planning permission. In particular, the aim is to analyse how the regulations actually influence project design, but also to understand their (non-)application in light of the numerous objectives set out in the texts, which can sometimes be contradictory. To this end, a comparative analysis of the practices involved in implementing town planning regulations in France and Germany should provide a better understanding of how these regulations are embedded within project dynamics and the interplay of stakeholders against a backdrop of global transformation. Whilst both countries have a strong planning culture, these are not identical, particularly due to their different institutional and administrative systems. This research will provide a better understanding of the practical role of regulatory urban planning in both countries, whilst also offering an operational perspective on the study of planning in Europe and its concrete effects.

Within the discourse framed by a commitment to energy transition, there is a growing emphasis on promoting energy flows at sub-urban scales between various activities. Local, national and transnational stakeholders are, for example, proposing to recover so-called ‘waste heat’ produced by a wide range of activities (industry, data centres, wastewater treatment, etc.). At the same time, there is a push to share decentralised energy production across different sectors (residential, tertiary, commercial, etc.) at scales ranging from the block to the neighbourhood. In short, forms of connection between urban activities for the exchange of energy are being promoted, and examples of their implementation are multiplying.

This thesis proposes to view these connections as new forms of urban networks, which are replacing or overlapping with a model of a large, centralised network that is over a century old, based on technical and economic efficiency, territorial integration and increased consumption. It aims to understand how the emergence of these local flows is changing the co-construction of the city and energy networks.

To understand these transformations, this thesis draws on two strands of research. On the one hand, urban and socio-technical research on networks helps to understand the reconfigurations of these infrastructures. On the other hand, the field of industrial and territorial ecology analyses the dynamics that lead to the exchange of material flows between human activities. Combining these findings thus enables us to understand the subject under consideration in its social, technical and metabolic dimensions, that is to say, from a socio-material perspective.

The analysis is based primarily on three case studies, focusing on understanding their emergence, operation and development: the supply of Dunkirk’s district heating network via an industrial heat source, heat recovery from a data centre to supply a neighbourhood in Marne-la-Vallée, and the pooling of energy production in the La Confluence neighbourhood of Lyon. More broadly, the study examines concrete or proposed reconfigurations of the organisation of the urban energy supply chain.

The findings of the thesis fall into three categories. Firstly, these networks are no longer driven solely by the technical and economic efficiency of the networked structure for supplying the region. The interests of the various actors involved all relate to the objective of optimising the use of flows: there is thus a shift from a quest for technical and economic efficiency to one of metabolic efficiency. Secondly, the networks emerging from these exchanges are unstable, particularly due to uncertainties regarding the short- and long-term evolution of available flows. Consequently, they do not replicate the unifying effect afforded by the stability of large conventional networks. Finally, in the face of these instabilities, the stakeholders propose developments aimed at reducing dependencies on uncertain flows. These developments are characterised by relying on network growth that no longer pursues a goal of universalisation. On the contrary, a strict spatial selection of network expansion is applied, based on the actuality of flows as perceived by the stakeholders. Rather than generating new consumption through a supply-driven approach, the aim is thus to integrate new flows already present in the region.

In short, the thesis highlights a certain ‘metabolic shift’ in the process of connecting the city through energy. Whilst the expansion of infrastructure has long been at the heart of network development, the flows of energy produced and consumed that already exist within the area may now be the primary motivation for establishing connections.

Members of the jury

• Sabine Barles, Professor, University of Paris 1 Panthéon-Sorbonne (rapporteur)
• Nicolas Buclet, Professor, Université Grenoble Alpes (examiner)
• Olivier Coutard, Research Director, CNRS, UMR LATTS (examiner)
• Gilles Debizet, Senior Lecturer, Université Grenoble Alpes (examiner)
• Gabriel Dupuy, Professor, University of Paris 1 Panthéon-Sorbonne (rapporteur)
• Laurence Rocher, Senior Lecturer, Université Grenoble Alpes (examiner)
• Taoufik Souami, Professor, University of Paris-Est (supervisor)

This thesis examines the conditions under which seismic risk emerges in Istanbul—before a seismic disaster strikes—by studying the interrelationships across geographical scales and the potential interactions between actors and stakeholders involved in this process. Particularly following the August 1999 earthquake in the Marmara region, the prospect of a potential major earthquake (olası depremi) in Istanbul has brought together the city’s key stakeholders to address the issue. The research draws on a qualitative study to closely track the operators (scientists, engineers, public institutions for planning and disaster management, construction and property firms, associations) who, in the sense of the sociology of science and technology, ‘take an interest’ in seismic risk. The increasing complexity of the concept of the ‘fabric’ allows us to reconceptualise the modes of interaction between risks and urban spaces in a joint manner, centred on two strands of analysis. The first strand explores the performative aspect of seismic risk, in order to understand how this risk structures the organisation of urban planning in Istanbul.

Against a backdrop of economic and political instability, vulnerable buildings present a challenge in terms of seismic risk and bring together stakeholders in the construction sector, whilst in turn fragmenting the professional world of urban planning. The second strand examines, at the neighbourhood level, the local assemblages at work in the construction of urban space, as material and social products of negotiations—whether settled or not—between urban planning stakeholders and residents and their representatives (neighbourhood mayors, associations, solidarity groups or disaster education centres). These highlight alternatives for managing risks based on new forms of knowledge.

Conversely, their re-institutionalisation at higher levels raises questions about the standardisation of local practices. The thesis highlights the complex relationships between risks that, on the face of it, belong to different categories. It emphasises the idea that, as seismic risk is interpreted and translated, seismic hazard becomes diluted within broader constellations of actors, entities and correlated risks. Through the lens of socio-technical systems, the thesis sheds light on the delicate coexistence of these risks in the same location, if not their intertwining or even friction.

Composition of the jury

• Laurent Devisme, Professor at ENSA Nantes (Rapporteur)
• Valérie November, Research Director, CNRS (PhD supervisor)
• Jean-François Pérouse, Senior Lecturer (HDR), University of Toulouse Jean-Jaurès (Examiner)
• Sezin Topçu, Research Fellow, CNRS CEMS-EHESS (Examiner)
• Elsa Vivant, Professor, Gustave Eiffel University (Examiner)
• Albena Yaneva, Professor, University of Manchester (Rapporteur)

This thesis in urban planning examines a public policy instrument designed to encourage the transfer of public and quasi-public land, which forms part of the wider trend towards negotiated urban planning: calls for innovative urban projects (APUI). These consultations have been the subject of much debate in academic and professional circles within urban planning, with some viewing them as a privatisation of planning, whilst others see them as a breath of fresh air in professional practice.

This thesis highlights how, for their initiators, APUIs function as instruments of remote governance despite the transfer of project management responsibilities to property developers, with ‘innovation’ helping to enlist the support of urban planning professionals. They constitute a response tailored to the circumstances of their initiators: evolving strategies for legitimising local government, a reduction in local authorities’ financial leeway, and the development of project-based approaches within contexts of fragmented governance. These consultations represent an attempt to modernise urban public action – and, by extension, public administrations. They temporarily reorient the operational logic of several professional sectors whose spheres of activity interact with one another.

To analyse the work currently underway, our analytical framework draws on various strands of sociological research: justification, translation, public action, management tools and activity. Drawing on ethnographic research, we highlight the challenges arising from the industrialisation of the ‘project mode’ and ‘innovation’ on the work of elected representatives, local public officials and project management assistants, from the launch of consultations through to the finalisation of winning property development projects: eventualisation and mobilisation, coordination challenges, and the legalisation and subsequent managerialisation of the public-private relationship. We highlight the pivotal role of artefacts in framing the activities of stakeholders. In doing so, we examine the reconfiguration of the tools, expertise and methods of operational urban planning driven by public initiative.

These findings provide broader insights into the changing priorities of professionals in the urban sector. We highlight an increase in media and networking activity, as well as a proliferation of intermediaries. These shifts call into question the meaning, resources and role assigned to expertise in shaping the relationship between public and private actors in the urban sector.

Composition of the jury

Véronique Biau – State-certified architect and urban planner (HDR), ENSA Paris-La Villette – LAVUE (rapporteur)
Alain Faure – Research Director, CNRS – PACTE (rapporteur)
Corinne Delmas – Professor, Gustave Eiffel University – LATTS
Laurent Devisme – Professor, ENSA Nantes – LAAU
Silvère Tribout – Senior Lecturer, University of Rennes 2 – ESO
Guillaume Tiffon – Professor, University of Evry Paris-Saclay – Pierre Naville Centre
Emilie Bajolet – Deputy Director of Consulting and Planning, AREP (guest member)
Elsa Vivant – Professor, Gustave Eiffel University – LATTS (supervisor)

In cities across sub-Saharan Africa, where the average rate of access to electricity stands at 60% to 70%, ensuring universal access to electricity remains a challenge. In this context, the development of the ‘large centralised grid’ – a priority for public authorities – and the proliferation of decentralised solutions, such as solar photovoltaic (PV) systems, are leading to hybrid urban electricity configurations. The thesis takes this observation as its starting point—the implications of which for electrification policies and the urban energy transition are still poorly understood—and aims to test the hypothesis of a forced adaptation of national electricity systems in cities experiencing rapid demographic and economic growth.
At the intersection of research from Transition Studies, urban political ecology and energy justice, it develops three lines of research. The first analyses how electrical hybridisation is concretely embodied in urban systems (technologies, actors, scales, territories, market mechanisms, regulatory and policy frameworks, etc.).

The second explores whether and how forms of governance emerge from this hybridisation, and examines the socio-technical representations and imaginaries that inspire them. The third examines how the rise of solar PV is shaped by urban socio-environmental inequalities and, in turn, impacts them, whilst simultaneously leading de facto to a redefinition of an essential service.

By focusing on the socio-technical interfaces between decentralised solutions and the wider grid as ‘sites’ for observing the transformations taking place, the methodology draws on a detailed inventory and mapping of the diverse modes of solar PV urbanisation, an analysis of the evolution of legislative and regulatory frameworks, and a study of actual practices regarding the installation and use of hybrid electricity access systems. Mindful of the power relations that shape these interfaces and the inequalities they engender, it also draws on tools for analysing the discourses and representations that accompany and influence the transformations underway. The primary field of investigation is the Dakar region in Senegal. This case study will then be placed in perspective alongside other urban contexts across the continent.

Neither an affiliation with a particular discipline nor access to specialised workspaces and instruments is sufficient on its own to define a scientific culture. What researchers from diverse backgrounds work on shapes a unique way of conceiving their activities, practices and relationship with the world. Their success is inextricably linked to a subject, and to the fortune that subject encounters as an innovation within a social context that both constrains and simultaneously shapes it. How is this (re)orientation towards a new thematic area organised, given that current trends in funding practices now specifically favour this framework? This thesis explores the concept of the ‘field of research’, which we define a priori as the framework for interactions between researchers’ professional activity and society around a shared theme; it argues for its epistemic dimension.

This thesis examines, in parallel, the development of bioenergy—one of the main forms of so-called renewable or sustainable energy derived from biomass—along with its key players and their strategies, against a backdrop of strong incentives to drive a global energy transition, yet also of intense social controversy. The two objectives of this thesis converge: describing the mindset inherent to a particular field of research is necessary to understand, beyond mere rhetoric and promises, the actual modes of innovation development (in this case, the large-scale mobilisation of plants, microorganisms or waste to produce biofuels) and, ultimately, to enable everyone to assess its relevance.

Members of the jury

• Marc Barbier, Research Director at INRA, PhD supervisor
• Céline Granjou, Research Director at IRSTEA, Rapporteur
• Bruno Latour, Professor at Sciences Po, Examiner
• Catherine Paradeise, Professor at the University of Paris-Est Marne-la-Vallée, PhD supervisor
• David Pontille, Research Director at the CNRS, Examiner
• François Vatin, Professor at the University of Paris-Ouest Nanterre La Défense, Rapporteur