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Soutenance de thèse

Marine Lanet

LMD

Évaluation des impacts régionaux du changement climatique et soutien à l'élaboration de stratégies d'adaptation : le cas du risque de feux de forêt dans le sud-ouest de la France

Date 25/11/2024 14:00
Diplôme Sorbonne Université
Lieu Sorbonne Université - Amphithéâtre Herpin (Bâtiment Esclangon)

Résumé

The reality of climate change is no longer in question. It is now widely accepted that we must not only reduce greenhouse gas emissions but also adapt to climate change, as some effects are unavoidable. However, these two goals can be achieved through different ways. Mitigating climate change can be effectively addressed through a top-down approach, such as by international agreements. Adaptation, on the other hand, is more effective through a bottom-up approach. Adapting a region requires considering a wide range of environmental, social, and economic interests. It is therefore essential to co-develop measures with stakeholders that account for local specificities. We need to narrow the gap between climate science and information needed for local adaptation. The aim of this thesis is to develop a bottom-up approach to pursue research that can provide local stakeholders useful climate information for adaptation.

We chose the Nouvelle-Aquitaine Region in France as our case study. In addition to traditional literature review to identify regional impacts of climate change, we also interviewed stakeholders to understand the local specificities, and the information that decision-makers would need to better anticipate climate risks. The pronounced seasonal hydrological cycle presents a significant challenge, particularly in the Landes Forest. The region experiences winter flooding and summer droughts. However, the interests of local stakeholders diverge regarding the strategies to adopt. This led us to develop a comprehensive analytical framework to assess the evolution of climate conditions, enabling the anticipation of various impacts affecting different stakeholders. It provides a common knowledge base from which we can initiate discussions to co-construct compromise solutions. Applied to southwestern France, this analytical framework reveals that extreme hot and dry conditions could become the norm by the end of the century. Such conditions are particularly conducive to the development of wildfires. For this reason, and because fire risk is one of the region’s major concerns, the second part of this thesis focuses on understanding and assessing the evolution of wildfire risk.

We studied firstly the role of climate change in the occurrence of the exceptional wildfires during the summer of 2022 in the region. We developed an index specifically designed to assess long-term climate drivers of wildfires, particularly compound hot and dry conditions. This index complements the commonly used Fire Weather Index (FWI). We found that anthropogenic climate change has doubled the likelihood of conditions such as those experienced in the summer of 2022. Finally, we assessed the evolution of fire risk using the newly developed index and the FWI under three climate warming scenarios. Results demonstrate the benefits of mitigating global warming. In the most pessimistic scenario, extreme hot and dry conditions that are currently propitious to wildfires could become the norm by the end of the century. In the most optimistic scenario, the probability of occurrence of such conditions increases to a much lesser extent. These findings also highlight the importance of implementing adaptation strategies, as the probability of conditions favourable to wildfires increases in all scenarios.

Overall, this PhD thesis offers a dual contribution. Methodologically, we developed research directions based on the need for climate information expressed by local stakeholders. We developed indices for the specific case of wildfires, which could also be adapted to other impacts. From an operational perspective, we provide local decision-makers with climate information to help them better anticipate the impacts of climate change. This work will be further developed, as several avenues for future research have been identified.

Informations supplémentaires

Lieu
Sorbonne Université
Campus Pierre et Marie Curie
4, place Jussieu Paris 5e
Bâtiment Esclangon – Amphithéâtre Herpin

Visio
https://cnrs.zoom.us/j/96405118473?pwd=NzcarVQMRSjsDYSvRF9CZ6445qSQHh.1
ID de réunion: 964 0511 8473
Code secret: AJk47H

Composition du jury

  • Sandrine Anquetin, Rapportrice
  • Mélanie Rochoux, Rapportrice
  • Hélène Chepfer, Examinatrice
  • Alain Dupuy, Examinateur
  • Denis Loustau, Examinateur
  • Jan Polcher, Examinateur
  • Hervé Le Treut, Directeur de thèse
  • Laurent Li, Co-directeur de thèse