Center for Environmental Economics - Montpellier - Monthly Publications feed

Economic Costs of Biological Invasions in Marine Systems

2026-05-11 15:09:37

Yu Liyi, Zhang Chi, Li Shan, Zhan Aibin, Katsanevakis Stelios, Haubrock Phillip J, Courtois Pierre, Kourantidou Melina, Tarkan Ali Serhan, Renault David, J. Dolan Ellen, Huang Hongkun, Zhang Yibo, Cuthbert Ross N., Liu Chunlong
Integrative Zoology
à paraître

Marine systems worldwide are suffering escalating impacts from biological invasions, with increasing threats projected for the future. Despite substantial financial investments in managing marine invasive species, knowledge of their impacts remains patchy across regions and organismal groups. A global assessment of economic costs is urgently needed to assess invasion risk, guide management, and identify knowledge gaps. We analyzed the total economic costs of marine biological invasions worldwide from 1975 to 2021, examining the distributions of costs across time, regions, and organismal groups. Over this period, marine invasive species have cost at least US$4.3 billion, with the majority (US$3.0 billion) resulting from resource damages rather than management investments. These costs revealed substantial geographic and organismal biases. While most entries (56.8%) were associated with invasive plants, most of the costs (76.7%) were linked to invasive invertebrates. Moreover, the majority of costs were driven by a single species within each organismal group. Economic costs were available for only 26 out of 146 coastal countries, with sporadic data from Africa and South America. Economic costs were positively associated with national GDP but unrelated to the number of invaders. Compared to terrestrial (US$2 trillion) and freshwater (US$104.8 billion) systems, marine systems had both lower numbers and magnitudes of economic costs, with all values referring to total costs between 1975 and 2021. These findings highlight the need for improved management and cost‐reporting systems to better address the impacts of marine invasions. In particular, management efforts should prioritize high‐risk species and highly vulnerable regions, with the development of species‐specific management strategies to enhance effectiveness. Moreover, proactive measures, such as strengthened regulations and pathway management, are crucial for reducing future risks and conserving marine biodiversity.

Modeling “Axiological Rationality” in Economics: A Tedious Challenge

2026-05-12 11:58:39

Serra Daniel, Benslimane Adda
Revue d'économie politique 136
2026

Is it possible to reconcile morality and rational behavior in economics? One interesting approach is to postulate that individuals are endowed with “axiological” rationality and not just “instrumental” rationality. The purpose of this article is to identify the main models in contemporary economic literature that seek to answer this delicate question in the affirmative by referring explicitly or implicitly to this concept. The article divides this literature into two sections: one covers models that treat morality as a normative concern (normative economics perspective), while the other covers models that treat morality as a social fact (positive economics perspective). The strengths and weak- nesses of these alternative models are evaluated in the light of their respective ambitions.

Do farmers trust digital decision support tools on pesticide use?Confiance et perception du risque dans l'usage d'un outil numérique d'aide à la décision pesticides Do farmers trust digital decision support tools on pesticide use?

2026-04-24 17:10:32

Cornier Alban, Bougherara Douadia, Thoyer Sophie
CEE-M Working papers WP 2026-09: 40 p.
2026

Les outils d'aide à la décision (OAD) sont de plus en plus mobilisés en agriculture pour raisonner l'usage des pesticides en fournissant des recommandations de traitement, souvent au jour près. Malgré les performances reconnues de ces outils, on constate que les agriculteurs suivent relativement peu les recommandations qu'ils fournissent. Cet article cherche à expliquer ces décisions à travers le prisme de la confiance en l'outil et des biais de perception du risque par les agriculteurs. Nous étudions le cas d'un OAD français destiné à la gestion du mildiou de la pomme de terre. À partir d'une base de données originale contenant les recommandations émises par l'OAD et les décisions de traitement des agriculteurs abonnés, nous analysons le suivi des recommandations de l'OAD par les agriculteurs ainsi que l'évolution de ce suivi à la suite d'épisodes de contamination par le mildiou. Nos résultats montrent que les agriculteurs suivent moins les recommandations de non traitement que celles qui recommandent de traiter. Ce résultat s'accentue pour les agriculteurs ayant subi une contamination dans le passé. On montre qu'ils choisissent de moins suivre les recommandations que l'OAD ait fait une erreur de prédiction dans le passé, ou non. Ces résultats suggèrent que le suivi ou non des recommandations est moins lié au niveau de confiance des agriculteurs dans l'OAD, que dans l'évolution de la perception du risque de contamination future, plus forte chez l'agriculteur ayant déjà subi une contamination dans le passé.

Myopic, farsighted behaviours and conjectural learning. Application to a groundwater exploitation problem

2026-05-11 15:09:37

Tidball Mabel, Jean-Marie Alain
CEE-M working papers WP 2026-10: 28 p.
2026

In this paper we consider two economic agents involved in strategic interactions between them and with the environment in a repeated interplay. They face to a lack of information about the profit of the other player, make conjectures on the opponent's behavior and optimize their utility accordingly. When observing the real behavior of their opponents they adapt their conjecture following a learning model. We consider here that players have a farsighted behavior in the sense that when making the conjecture they maximize their discounted profit in infinite horizon assuming the other player behaves as prescribed by her conjecture. The main result is that the fixed points of the conjectural learning model are also the steady states of the corresponding Pareto-optimal complete-information solution for appropriately chosen Pareto weights. A similar result is obtained as a particular case when players are myopic. We apply this procedure to a groundwater management problem and perform some simulations for testing the consequences on profits and dynamics when varying some parameters of the conjecture.

From debt crises to financial crashes (and back): a stock-flow consistent model for stock price bubbles De la crise de la dette au crash financier (et retour) : un modèle à cohérence stock-flux des bulles de prix d'actifs

2026-05-11 15:09:37

Grasselli Matheus R., Nguyen-Huu Adrien
CEE-M working papers WP 2026-11: 38 p. + annexes
2025

We develop a stochastic macro-financial model in continuous time by integrating two specifications of the Keen economic framework with a financial market driven by a jump-diffusion process. The economic block of the model combines monetary debt-deflation mechanisms with Ponzi-type financial destabilization and is influenced by the financial market through a stochastic interest rate that depends on asset price returns. The financial market block of the model consists of an asset with jump--diffusion price process with endogenous, state-dependent jump intensities driven by speculative credit flows. The model formalizes a feedback loop linking credit expansion, crash risk, perceived return dynamics, and bank lending spreads. Under suitable parameter restrictions, we establish global existence and non-explosion of the coupled system. Numerical experiments illustrate how variations in credit sensitivity and jump parameters generate regimes ranging from stable growth to recurrent boom--bust cycles. The framework provides a tractable setting for analyzing endogenous financial fragility within a mathematically well-posed macro--financial system.

Strategic Fossil Expansion and the Timing of the Energy Transition

2026-05-12 11:40:21

Prieur Fabien
CEE-M Working papers WP 2026-12: 35 p.
2026

We develop a dynamic game of exhaustible resource exploitation with exploration, in which a regulator determines the end date of the fossil regime by trading off industry profits against climate damages. The weight assigned to damages reflects the fossil industry's political influence. We compare the open-loop Nash equilibrium with the piecewise closed-loop Nash equilibrium in which the regulator adopts a state-contingent stopping rule. In the open-loop equilibrium, regulation shortens the fossil regime and reduces cumulative emissions relative to the unregulated benchmark. But extraction is front-loaded: emissions are higher at each date within the shorter exploitation period. In the piecewise closed-loop equilibrium, a monopoly may increase exploration relative to the open-loop outcome in order to delay the transition. Strategic expansion arises when the regulator's stopping rule is locally increasing in reserves and when the private marginal value of exploration is sufficiently low. Calibrating the model to global oil market data, we show that the implied distortions can be economically meaningful. The analysis thus provides an explanation for sustained upstream fossil fuel investment despite announced net-zero commitments.

Bioeconomic Viability and Resilience of Agroforestry Systems

2026-05-18 16:11:33

Darius Mba Alex, Valaire Yatat-Djeumen Ivric, Doyen Luc, Ekue Marius
CEE-M Working papers WP 2026-13: 25 p.
2026

Agroforestry systems consist in the combination of farming and forestry landuse. This study deals with the sustainable and resilient management of agroforestry systems. We consider a stylized dynamic model capturing non-linear tree-crop interactions and controlled by tree and crop harvesting. We assess the sustainability of the system through bioeconomic viability constraints of food security, economic profitability, and biodiversity. A first analytical result relating to coupled MSY-MEY (Maximum Sustainable Yield-Maximum Economic Yield) reference points and strategies provides sufficient conditions for the non-emptiness of the viability kernel. A second result highlights a viable window, not limited to the steady states, and stressing multiple sustainable balances between tree and crop land-use for agrosystems. Viable harvesting management are deduced, in particular to maintain the tree density between specific safe boundaries. A third result informs on the resilience of the agroforestry system through both stability and recovery analysis with respect to the viable window. Numerical simulations based on Cameroonian cocoa agroforestry illustrate these theoretical insights in a tropical context.