On the occasion of the second Dialogue of the Chair Living within Planetary Boundaries, held on 1 June 2026 at the Nantes National School of Architecture (ENSA Nantes), Lucie Renou of the Nantes Urban Planning Agency (AURAN) reflects on the discussions and key ideas that shaped this event.
On 1 June 2026, AURAN co-organised, together with the partners of the Chair Living within Planetary Boundaries, a Dialogue between geochemist Jérôme Gaillardet and anthropologist Verónica Calvo Valenzuela around a question that has become increasingly urgent in the face of environmental change: how can we rethink the habitability of our territories?
Inspired by the work of Bruno Latour, particularly his call to "land" in a world confronted with a new climate regime, the event brought into conversation two disciplines that have long evolved separately: Earth sciences and the social sciences and humanities. It explored both the conditions that make a territory habitable today and the transformations required to ensure its habitability in the future.
Fabrice Rodriguez, a hydrologist and researcher at the Nantes Observatory of Urban Environments (ONEVU) within IRSTV and OSUNA, contributes his own perspective, extending these reflections through the lens of urban environmental observation.
As part of the Second Dialogue of the Chair Living within Planetary Boundaries, held on 1 June 2026, Transitions Urbaines produced a podcast episode to extend the conversations initiated during the event. The episode features contributions from Verónica Calvo Valenzuela and Jérôme Gaillardet, revisiting the key questions and themes explored during their dialogue.
Transitions Urbaines is a Nantes-based association that documents and analyses contemporary territorial transformations. Through field investigations, editorial publications, and audio productions, it explores emerging practices in urban planning, ways of living, and ecological transitions, giving voice to a wide range of contributors, including researchers, practitioners, and public decision-makers. This work forms part of an ongoing collaboration between Transitions Urbaines and the Chair, built around shared interests: observing territorial change, fostering dialogue between research and practice, and making these reflections accessible to a wider audience.
The Critical Zone: A New Perspective on Territories
At the heart of the discussion was the concept of the Critical Zone. Developed within the Earth sciences, it refers to the thin layer of our planet where water, air, soils, rocks, living organisms, and human activities interact. It is within this narrow envelope that all the processes making life possible take place.
For Jérôme Gaillardet, the Critical Zone invites us to move beyond sector-based approaches and to understand the interdependencies that shape our territories. Soils, groundwater, rivers, vegetation, and human infrastructures cannot be considered in isolation. They are all part of a single dynamic system, of which humans are an integral part.
This perspective also challenges categories inherited from modern thought, particularly the distinction between nature and society, or between the living and the non-living. The Critical Zone is not merely the backdrop against which human activities unfold. It is the very system upon which the habitability of our world depends.
Living Means Recognising Interdependencies
Verónica Calvo Valenzuela's research, particularly her work in the Bolivian Andes, offered a complementary perspective on these questions. Through her study of Andean cosmologies, she shows how certain societies understand mountains, water, soils, and living beings as active participants in maintaining the balance of a territory.
Far from being a folkloric interpretation, these worldviews reflect a deep attentiveness to the relationships that make life possible. Rituals, agricultural practices, and forms of collective organisation all serve as ways of recognising and sustaining the interdependencies between humans and non-humans.
In other words, rather than opposing scientific knowledge and local knowledge, this dialogue highlighted different ways of making visible the often invisible relationships that enable a territory to remain habitable.
For Verónica Calvo Valenzuela, habitability cannot be reduced to a set of thresholds or technical indicators. It is also a political question: how can we collectively define the conditions for a livable world? Which forms of knowledge, experiences, and voices should be brought together to shape this shared horizon?
Water as the Thread Connecting Territorial Timescales
Water emerged as one of the key points of convergence between the two perspectives.
For Jérôme Gaillardet, water is one of the fundamental drivers of Earth's habitability. As it circulates between oceans, the atmosphere, soils, vegetation, and the subsurface, it shapes landscapes, weathers rocks, sustains ecosystems, and regulates the climate. These processes, however, unfold across vastly different timescales, ranging from a few days to millions of years.
Time was therefore a central theme of the discussion. Human activities are now accelerating many natural cycles. The burning of fossil fuels, the drainage of wetlands, and soil sealing are profoundly altering the rhythms of the Critical Zone. For both speakers, one of the defining challenges of our time is to regain a degree of synchronisation with these long-term temporalities.
The Andean narratives discussed by Verónica Calvo Valenzuela likewise reflect a deep awareness of the relationships between water cycles, soil fertility, the seasons, and human life. They remind us that habitability depends not only on understanding these interdependencies, but also on our ability to sustain them through everyday practices.
Describing Territories from Within
These reflections have directly informed the territorial self-description workshops developed during the second year of the Chair Living within Planetary Boundaries, following the work of Bruno Latour.
As part of the Chair's second year, Verónica Calvo Valenzuela led two workshop groups bringing together around fifteen participants, including practitioners, researchers, and students working on issues related to territorial planning and development. Each group took part in around ten workshop sessions between September 2025 and June 2026. Participants were invited to describe the entities to which they feel attached, whether a river, a landscape, a collective practice, or a form of hospitality, as well as the threats they face and the alliances needed to protect them. The aim was not to produce a diagnosis, but to gain a deeper understanding of the interdependencies that shape the ways we inhabit and engage with our territories.
The first findings from the workshops held in Nantes highlight the importance participants attach to elements as diverse as the Loire River, collective action, hospitality, conviviality, sleep, gardens, and shared practices. Beneath this diversity, common concerns emerge around rootedness, regeneration, the quality of social relationships, and our relationship with water.
These workshops invite us to view territory not simply as a physical space, but as a network of relationships, attachments, and dependencies that together shape its habitability. They open new ways of thinking about territorial planning, moving beyond conventional distinctions such as nature and society, visible and invisible, or human and non-human, and instead focusing on the relationships that connect them.
What the Critical Zone Changes for Territorial Planning
A discussion with the audience explored the practical implications of these approaches for professionals working in territorial planning and urban development.
The conversation first highlighted the difficulty of moving beyond the siloed structures that still largely shape public action. Although more integrated approaches are emerging, they often remain organised within separate disciplinary or institutional frameworks. Several participants stressed the need to better connect scientific knowledge, professional expertise, and residents' lived knowledge.
The discussion also brought new objects of observation into focus. Alongside conventional environmental data, participants pointed to birds, local narratives, territorial memories, everyday practices, sensory perceptions, and relationships with water as valuable sources of insight. Several speakers emphasised that observation does more than generate knowledge; it also helps bring these subjects into public debate.
Finally, the question of narrative emerged as a central issue. How can we develop a shared language between researchers, practitioners, elected representatives, residents, and users of a territory? How can lived experience and personal attachments become part of the way we understand places? Faced with the growing fragmentation of knowledge, several participants called for new forms of translation, both across academic disciplines and between the different communities involved.
Observing the Urban Critical Zone from Nantes
These reflections take on a concrete dimension in the work presented by Fabrice Rodriguez, head of the Nantes Observatory of Urban Environments (ONEVU).
For the past twenty years, the observatory has documented the flows of water, energy, and pollutants moving through several urban sites. Its approach seeks to observe the different components of the Critical Zone together, including the atmosphere, surface environments, subsurface layers, vegetation, waterways, as well as urban infrastructure and technical networks.
Research conducted in the Chézine watershed, the Prairie de Mauves, and neighbourhoods incorporating alternative stormwater management systems illustrates the value of this approach. These studies provide a better understanding of the interactions between urbanisation, climate change, soil quality, water resources, and urban heat islands.
The observatory's findings also highlight the crucial role of underground processes, which often remain invisible, in shaping the way territories function. They remind us that the city itself can be understood as an integral component of the Critical Zone.
