Description du sujet de thèse

What service packages do restored grasslands offer in agricultural landscapes? The case of the Gers basin (Southwest France)

Thesis context:
Today, certain human activities are radically altering ecosystems and their functioning (climate disruption, biodiversity loss) and compromising the sustainability of socio-ecological systems. This is particularly the case with extractive agricultural activity, which prioritizes agricultural yields at the expense of the quality and sustainability of terrestrial and aquatic ecosystems. Adopting more ecosystem-friendly practices relies on achieving compromises between economic outcomes and ecosystem functioning, which provide ecosystem services (services provided by nature and essential to human survival and well-being). In cases where ecosystems are destroyed or excessively degraded, Nature-Based Solutions, such as the restoration of permanent and diversified grasslands, could help restore ecological functions and therefore ecosystem services such as water quality, erosion control, pollination, and crop protection. This thesis is part of the COMSYSE project (COMpromis et Synergies entre Services Ecosystémiques), which has the particularity of being based on two theses: one in economics, the other in ecology. In the COMSYSE project, we propose to better understand how trade-offs between economic performance and environmental preservation can be formulated to maintain a certain economic efficiency while adopting a form of equity within socio-ecosystems for an economy with high human and ecological value. To this end, we have developed an approach in which the results of two thesis projects in economics and ecology will be regularly discussed over the three years of its implementation to foster interdisciplinary reflection. Both theses will share the same study area: the southern Gers region. 1/ The economics thesis project will focus on an assessment of ecosystem services perceived by residents of the study area and an analysis of trade-off definition mechanisms. 2/ The ecology thesis project, which is the subject of this call for applications, will focus on the ecosystem service packages provided by restored grasslands in agricultural landscapes.

Thesis objectives:
The objective of the ecology thesis is to measure and model the service packages provided by restored grasslands in agricultural landscapes. It will be co-supervised by the CRBE (https://crbe.cnrs.fr/) for the hydrological modeling component and by the Dynafor laboratory (https://www.dynafor.fr/) for the pollination component. The study area will be located in the southern Gers region, in an area where the hydrological model has already been calibrated and where meadow restoration operations are being carried out as part of the Living lab Coteaux Gascons led by ADASEA du Gers, a partner in the COMSYSE project. The thesis will be structured in three parts, with increasing interdisciplinarity with the economics thesis. In the first part, the benefits of meadow restoration for water quality, pollinators, and pollination will be measured on approximately fifteen restored meadows via pollinator monitoring transects and water quality monitoring in small pilot watersheds for a subsample of restored meadows. The pollination gain will be estimated using modeling (Desaegher et al., 2021) (the "Pollination" module of the InVest platform, configured for the region and already in use at the Dynafor laboratory). In a second part, the objective is to test a possible synergy between the pollination service and the improvement of water quality by hypothesizing that a possible drop in yield, and therefore in farmers' income, due to a reduction in the use of synthetic fertilizers and pesticides could be offset by an improvement in yield through ecosystem services. This compensation effect would occur via better pollination, which can increase yield by up to 30%, which would be made possible by the combined effect of meadow restoration and moderate pesticide use (50% reduction, EcoPhyto objective). Italian work has already shown that optimal levels of pollination offset losses due to a reduction in fertilizer use (Tamburini et al., 2017). The beneficial effect on water quality will be estimated based on an existing model, developed and parameterized for the area by the CRBE laboratory. The use of a microeconomics model and collaboration with the economics thesis will allow us to verify that this does not impact farmers' income. Finally, the last section will expand on other services to consider the range of services offered by grassland restoration, considering other services cited by local stakeholders in the economics thesis and not studied in the first two chapters of the ecology thesis, such as carbon storage, landscape amenities, etc. This final section will address the synergies and trade-offs between these services and will focus on determining whether these ranges are balanced or whether different service range profiles are identifiable in the context of current landscapes (Bennett et al., 2009) and possible or desired evolution scenarios for these landscapes.

Bibliography
EM Bennett, E.M. Peterson, G.D., Gordon, L. G. 2009 Understanding relationships among multiple ecosystem services. Ecology letters 12 (12), 1394-1404
Desaegher, J., Sheeren, D., Ouin, A. 2021 Optimising spatial distribution of mass-flowering patches at the landscape scale to increase crop pollination. J. Appl. Ecol. 58:9, 1876-1887.
Tamburini, G., Francesco, L. Lorenzo, M. 2017 Pollination benefits are maximized at intermediate nutrient levelsProc. R. Soc. B.28420170729

Contexte de travail

Thesis Funding
This thesis is co-funded by the Occitanie region through the COMSYSE project and by the Solubiod National Research Program on Nature-Based Solutions (https://www.pepr-solubiod.fr/).

Thesis Supervision and Methodological Support
Dual supervision is planned (CRBE and DYNAFOR), as well as methodological support, which will also be provided by both laboratories to ensure consistency in the approaches and tools used in each discipline. Additional training in interdisciplinary methodologies will be offered to strengthen the ability to collaborate effectively.
A collaborative digital data-sharing platform will be established to facilitate the exchange of data and results between CRBE, DYNAFOR, and LEREPS, the latter being the lead researcher for the Economics thesis (database sharing, shared analysis documentation, and a discussion space for discussion). Popularization and dissemination seminars will allow feedback from the field to be integrated into the research process, promoting a participatory approach to implementing solutions. In addition, a final conference will be held at the end of the project.
Funding is planned for participation in at least one international scientific conference and the opportunity to spend several weeks in a foreign laboratory related to the topic addressed in the thesis.

Thesis location: the CRBE (French Research Centre for Biodiversity and Biotechnology) on the INP-Agro-Toulouse site (https://www.ensat.fr/fr/index.html). The Dynafor laboratory is also located on this site.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.

Contraintes et risques

According rules and regulations by the laboratory

Informations complémentaires

Required skills:
- Numerical modeling, data processing (Python and/or R)
- In situ experiments/observations of biodiversity and/or water quality

Required knowledge:
- Hydrology, ecology, ecosystem services
- Modeling techniques
- Affinity for digital technology and field observations
- Interest in interdisciplinarity with the social sciences