Center for Environmental Economics - Montpellier - Monthly Publications feed

The Need for Improved Public Transparency in the Era of Due Diligence Regulations

2026-03-23 11:02:21

Guye Valentin, Meyfroidt Patrick, Ermgassen Erasmus Zu
Regulation and Governance
à paraître

To address environmental and human rights issues in global commodity supply chains, governments increasingly require information from companies on their sourcing, as part of due-diligence regulations (DDRs). This shift towards accountability to the regulator rather than to the public calls into question the role left for public transparency. In this perspective piece, we argue that public transparency is actually complementary to DDRs-addressing their incomplete coverage of global supply chains and sustainability issues-and corrective to DDRs-mitigating their undesirable side effects. We illustrate these points with data on West African cocoa supply chains. Public transparency thus remains crucial for supply chain sustainability governance in a DDR era, and we encourage stakeholders to keep demanding its improvement.

Forest management plan validation gradually reduces forest loss in Congo Basin concessions

2026-03-30 11:46:11

Houngbedji Kenneth, Bouvier Marc, Leblois Antoine, Makak Jean-Sylvestre, Mertens Benoit
Communications Earth & Environment
2026

Forest management plans are central to regulations governing logging concessions in the Congo Basin, yet their long-term effectiveness remains uncertain. Here, we combine annual satellite-derived forest change data with administrative concession records and exploit variation in the timing of plan validation across five countries to assess how validation influences forest-cover dynamics from 2000 to 2020 using counterfactual impact-evaluation methods. We find that concessions with validated plans experience a gradual, sustained decline in forest loss, averaging 100 ± 44 hectares per year, equivalent to a 47% reduction relative to concessions operating without validated plans. Effects persist for up to 19 years and occur in concessions with and without independent third-party certification. These results indicate that accelerating the validation and implementation of forest management plans can substantially reduce forest disturbance in the Congo Basin.

Revisiting Stackelberg in His Own Light: Conjecture Learning in Leader-Follower Games

2026-03-30 11:46:11

Claude Denis, Tidball Mabel
International Game Theory Review
à paraître

This paper revisits Heinrich F. von Stackelberg's original description of leader-follower games under incomplete information, exploring how learning dynamics shape strategic interaction. The leader iteratively updates its conjecture about the follower's reaction function before choosing an activity level that maximizes its payoff. The follower, in turn, responds optimally to each activity level, revealing information that the leader uses to refine its conjecture. Assuming linear conjectures, a smooth updating process à la Jean-Marie and Tidball [2006], and quadratic payoff functions, we establish conditions under which the learning process converges asymptotically to a self-confirming steadystate. We characterize the resulting activity levels and payoffs in two canonical environments: a sequential partnership game and a sequential duopoly game with quantity competition. We then compare the learning outcomes to both the (complete information) Stackelberg and the cartel solution. In the process, we find conditions under which the lack of information and the resulting strategic ambiguity lead to higher joint payoffs, and under which usual intuitions about the first-mover advantage need qualifications.

A priming nudge targeting innovative farmers: A large-scale survey experiment

2026-03-30 11:46:10

Bougherara Douadia, Gosset Léa, Préget Raphaële, Thoyer Sophie
PLoS ONE 21: e0345658
2026

This article measures farmers' innovativeness and the effectiveness of a priming nudge on their (stated) intention to adopt an innovation, namely the French "Low-carbon label" (LCL). The LCL is an innovative certification framework that provides farmers with a potential new "green business model," enabling them to generate income through the sale of certified carbon credits earned by reducing their own greenhouse gas (GHG) emissions. Using 6,005 responses to an online survey with French farmers, we validate an original scale designed to measure farmers' capacity to innovate and find that innovativeness is positively correlated with stated intention to adopt the LCL. We then evaluate with a randomized experiment included in the questionnaire the net impact of a priming nudge, defined as exposure to a lexical field designed to unconsciously activate psychological factors, and implemented here with references to innovation in order to target the most innovative farmers. We show that the nudge has no detectable impact on the surveyed sample: it neither increases adoption intentions among the most innovative farmers nor discourages the less innovative ones. This absence of effect leads us to discuss the effectiveness of nudges when trying to influence farmers' high-stakes decisions.

Environmental regulations and spillovers across ecosystems: Fisheries and forests protection in coastal Madagascar *

2026-03-31 13:54:11

Girard Julia, Desbureaux Sébastien, Lavaine Emmanuelle, Leblois Antoine, Razanakoto Thierry
CEE-M working papers WP 2026-04: 87 p.
2026

Policy analyses often treat ecosystems in isolation, overlooking the complex interconnections that define socio-ecological systems. However, conservation measures in one ecosystem may produce unintended spillover effects in another-a phenomenon that remains poorly understood. This dynamic could be particularly important in coastal regions, where one billion people live, many of whom rely on access to both fisheries and land resources for their livelihoods. In Madagascar, where agricultural expansion commonly occurs through forest conversion, we wonder if increasing the protection of one of these resources, fisheries, results in greater use and pressure on another resource, forests. We conducted a household survey of 1,120 households across 41 villages. The results show that spillovers between marine and terrestrial resources are likely to occur but that increasing the regulation of marine resources can have an ambiguous effect on deforestation. Next, we combine matching and difference-in-differences models to quantify the effect of creating 200 locally managed marine areas on deforestation across the entire country over 17 years. We find that spillovers do occur in terrestrial areas following the interventions and, on average, lead to a 68% increase in forest cover loss. This increase in deforestation is more pronounced in remote areas, in regions with greater baseline forest cover, and in places that receive less precipitation.

Group-level cooperation

2026-03-16 18:35:36

Quérou Nicolas
CEE-M Working Papers WP 2026-05: 36 p.
2026

We analyze the existence, coordination and efficiency effects of group-level cooperation in games featuring heterogeneous strategic spillovers and externalities within and between groups of agents. Conclusions depend on whether out-group interactions feature strategic substitutes or complements. Under high out-group strategic spillovers, group-level cooperation triggers either equilibrium existence or coordination issues. When these effects are not too high, a unique group-level cooperation equilibrium exists and its characterization depends on the in-group externality level. With respect to efficiency, cases are characterized under which this initiative is self-enforcing. Conditions are also provided under which it backfires: the cooperating group members would be actually better off if they could ex-ante commit to not cooperate, even if it would be costly to do so.

Optimal resource allocation for invasive species control: Two decision criteria for site prioritization

2026-03-23 14:20:33

Courtois Pierre, de Frutos-Cachorro Julia
CEE-M working papers WP 2026-06: 22 p.
2026

Invasive species management is often guided by the implicit assumption that minimizing the invaded population will concurrently minimize the economic and ecological damages it causes. However, this alignment is challenged when damages are spatially heterogeneous, raising a critical question for environmental managers: should limited control budgets prioritize sites to minimize invasion state or damage? This paper defines and compares two simple cost-effective decision criteria for site prioritization: an invasion-minimization criterion, which targets sites based on their per-unit-cost contribution to future invasion spread, and a damageminimization criterion, which targets sites based on their per-unit-cost contribution to future damages. We solve analytically the two optimization problems and derive the restrictive theoretical conditions under which these criteria yield identical rankings. Applying these criteria to the management of Primrose willow (Genus Ludwigia) in the Brière Regional Park in France, we demonstrate that for a realistic budget, the two criteria lead to starkly different spatial allocations of effort. The damage-minimization criteria concentrates resources in a few high-value, highly invaded areas, while the invasion-minimization criteria spreads effort across many more, less valued areas to curb overall invasion state. Our analysis reveals that the common managerial practice of prioritizing population reduction may not align with damage reduction objectives unless damages are uniform or dispersal networks are trivial. This work provides clear, operational decision rules and highlights the need for explicit consideration of management objectives and spatial heterogeneity in the economics of biological invasions.

Une courte note sur l’évolution des pratiques de l’économie expérimentale au cours de la dernière décennie

2026-03-30 11:46:11

Serra Daniel
CEE-M working papers WP 2026-07: 3 p.
2026

La Revue de philosophie économique a publié en 2025 un numéro spécial pour son Vingt-cinquième anniversaire. Parmi les auteurs des 25 articles retenus pour illustrer la place que la revue a jouée dans l’évolution de la pensée économique depuis sa création en 2000 figurent des chercheurs aussi prestigieux que John Rawls, Amartya Sen, Jean-Pierre Dupuy ou Philippe van Parijs. L’ouvrage inclut aussi, entre autres, un article de Daniel Serra intitulé « Principes et pratiques de l’économie expérimentale : une vue d’ensemble », publié en 2012. Le complément à l’article qui devait initialement être joint n’ayant pu l’être pour des raisons d’édition, il est diffué ici sous forme de note