PhD Defence. Gildas Bopahbe Deudibe

Gildas Bopahbe Deudibe
CERDI, Université Clermont Auvergne

Examiners

Pascale Motel Combes, Professor, Université Clermont Auvergne.
Jean-Louis Combes, Professor, Université Clermont Auvergne.
Gervasio Semedo, Professor, Université de Tours.
Samuel Guérineau, Professor, Université Clermont Auvergne.
Eric Rougier, Professor, Université de Bordeaux.
Jean-Sébastien Pentecôte, Professor, Université de Caen Normandie. 

Abstract

Climate change is no longer perceived solely as an environmental issue, but also as one of the major economic challenges. Developing countries face a double bind: high exposure to climate risks and limited institutional and financial capacity to address them. This thesis analyzes the relationship between climate vulnerability and economic performance using an integrated macroeconomic and microeconomic approach. The central objective is to assess how climate shocks influence sovereign debt dynamics, fiscal policy effectiveness, food security, and welfare distribution.

The thesis is structured around four essays. The first essay analyzes the relationship between vulnerability, climate resilience, and the cost of sovereign debt in developing countries over the period 1995–2021. Panel estimates show that climate vulnerability significantly increases bond spreads, while resilience reduces them. The effect of resilience appears asymmetric and more powerful, suggesting that investment in adaptive capacity and institutional quality yields tangible financial dividends. These results indicate that financial markets are increasingly incorporating climate risks into sovereign risk assessments, thereby exacerbating the fiscal constraints faced by vulnerable countries. The second study examines fiscal multipliers in sub-Saharan Africa. The analysis highlights the non-linearity of these multipliers: moderate fiscal shocks generate the most significant effects on output, while shocks that are too small or too large produce attenuated or even negative results. Multipliers linked to public investment are higher and more persistent than those related to public consumption, but their effectiveness is reduced when financing relies on excessive debt or distortive taxation. These findings underscore the need to adapt fiscal strategies to the specific characteristics of African economies highly exposed to climate shocks. The third study focuses on Chad, a Sahelian country particularly vulnerable to climate variability. Using a pseudopanel, the study demonstrates that food insecurity is persistent and structural, with little upward mobility between categories. Rainfall shocks and rising temperatures exacerbate this insecurity, while household adaptation strategies (selling livestock, reducing food consumption, dropping out of school) often worsen long-term poverty traps. This observation underscores the inadequacy of short-term survival mechanisms and the need to invest in structural adaptation policies, particularly irrigation, education, and income diversification. The fourth study uses a microsimulation model to assess the distributional effects of climate shocks in Gabon. The results show that the poorest households are the most affected, due to the high proportion of food and energy expenditures. Adaptation scenarios reduce negative effects but require significant budgetary resources, illustrating the tension between financial constraints and social equity. This study demonstrates how macroeconomic shocks translate into differentiated impacts on household well-being.

Together, these four studies confirm the cross-cutting nature of climate risk. They show how climate vulnerability is built into financial markets, how it constrains the effectiveness of fiscal policies, how it perpetuates structural food insecurity and how it exacerbates distributive inequalities.

Keywords

Fiscal policies, environmental policies, debt, food security, microsimulation.