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Intitulé du projet: Modélisation multi-échelles et multi-disciplinaire des socio-écosystèmes

Il s'agit du projet phare 5 de la 1ère phase (2013-2016) du LabEx BASC. 

Porteurs : Pierre-Alain JAYET (Economie Publique), Paul LEADLEY (ESE), Benjamin LOUBET (ECOSYS) & Olivier MARTIN (GQE-Le Moulon)

Ce projet a trois objectifs liés à l’animation de la recherche au sein de BASC et à la résolution des questions en suspens dans le développement et l’application de modèles complexes des socio-écosystèmes (SES) :

• identifier l’ensemble des modèles disponibles au sein de BASC ainsi que leurs utilisateurs et les personnes responsables de leur développement ;
• intégrer des modèles à travers les disciplines en développant un cadre conceptuel pour des modèles de SES interdisciplinaires, ainsi que des outils pour coupler les modèles existants ;
• utiliser des outils conceptuels, mathématiques et informatiques innovants pour répondre aux défis de la modélisation multi-échelles et étudier la propagation de l’incertitude dans ces modèles.

Développer des modèles de SES couplés de façon dynamique

L'un des objectifs du Projet Phare 5 de BASC est d'étudier les socio-écosystèmes (SES) par le couplage de modèles décrivant les composantes i) climat, atmosphère et hydrosphère, ii)  fonctionnement des écosystèmes et biodiversité et iii) économie, politiques publiques, et gestion et utilisation des terres. Deux échelles spatiales de prédilection ressortent des travaux actuels menés dans BASC : i) l'échelle de couverture du paysage couvrant quelques km² et ii) l'échelle de couverture régionale allant de 10000 km² (≈ échelle territoriale) à plusieurs millions de km² (≈ échelles nationales à subcontinentales).

Les modèles développés dans BASC permettent d’envisager d’aborder des questions scientifiques novatrices qui intègrent la complexité des systèmes socio-écologiques à travers le couplage, dynamique ou non, de modèles de fonctionnement des systèmes agricoles et non-agricoles (ex : CERES-EGC, STICS, ORCHIDEE, CASTANEA, …), de modèles de climat / atmosphère / hydrosphère (ex : MDz, MORCE-WRF, INCA, Chimère, Nitroscape...), et de modèles d'économie / politiques publiques / gestion et utilisations des terres (ex : modèle agro-économique AROPAj, modèles économétriques...). Les sorties de ces modèles couplés devront permettre de répondre à des enjeux écologiques, économiques et environnementaux.

Développer un cadre conceptuel et méthodologique pour gérer des systèmes multi-échelle complexes

Il s’agit ici de mener une recherche hautement exploratoire utilisant un cadre méthodologique commun pour quantifier la résilience des SES et de leurs composants. L’objectif n’est pas de développer des modèles prédictifs, mais de fournir un cadre conceptuel et théorique qui facilite et stimule le dialogue interdisciplinaire et sensibilise la communauté BASC à l’importance des propriétés émergentes et de la propagation des incertitudes dans les systèmes multi-échelles complexes.

Deux profils ont été définis afin de faire avancer ces travaux :

> Post-doctorat « Couplage de modèles » - Marc Stéfanon – 36 mois

> Ingénieur « Rationalisation des bases de données pour la simulation des systèmes couplant économie, écologie, fonctionnement de la biosphère et de l’atmosphère » - Juliette Adrian – 24 mois

Résultats

The objective of the BASC Flagship Project 5 (FP5) was to mobilize the community of scientists within BASC and associated with BASC to develop and apply coupled climate-land systems models (also referred to as "socio-ecological systems" models) at landscape to regional scales that couple climate, air quality, ecosystem functioning, biodiversity, land use and economics. Five activities contributed to achieving, at least partly, these objectives:

1. Organization of workshops bringing modelers together from a wide range of disciplines to create the foundations for building coupled climate-land system models. Several workshops created essential interdisciplinary collaborations and laid out strategies for building coupled climate- land system models. The workshops did not lead to a new coupled climate-land system model being developed within the timeframe of the project, which was the original goal, but they did establish the foundations for a flagship project in the second phase of BASC (STIMUL) that has a concrete framework for developing such model couplings. Workshops also contributed to structuring the scientific community that put together the successful proposal for the "Institut de Convergence CLAND". 

2. Creation of an on-line catalog of models developed and/or used by BASC teams. This web-based catalog — accessible on the Labex BASC web site — consists of short, structured descriptions of models used by BASC teams to simulate various components of the climate-land system interactions.

3. Demonstrations of the importance of coupling models for understanding climate-land system interactions. These studies demonstrated that i) land use can, under certain circumstances, have impacts on regional climate that are on roughly the same magnitude as those due to global climate warming, ii) ecosystem models can provide a powerful means of testing regional climate models, and iii) fully integrated models of land use and climate drivers of species distributions can substantially alter the understanding of the factors underlying presence and absence.

4. Mobilization of databases as the basis for building coupled models. A new model has been developed that couples a model agricultural offer with a simplified version of a mechanistic crop production model at the European scale. This work required the mobilization of a wide range of agricultural, environmental and economics databases supported by FP5. This model provides a means of testing the impacts of agricultural policy and management practices on farming economies and crop production for Europe.

5. Building international collaborations with other teams working on coupled land system models. BASC FP5 helped support the organization of and participation in an on-going international effort to couple global socio-economic development models (in particular the "Shared Socio- economic Pathway" scenarios being developed in support of IPCC) with models of impacts on ecosystem function and biodiversity.

==> Accédez à la présentation powerpoint des résultats du projet phare 5 lors (Journées 2017 du LabEx)

Pages web

L'inventaire non exhaustif des modèles disponibles au sein de BASC, avec fiches synthétiques est consultable ici.

Publications 

> Lemordant, L., P. Gentine, M. Stefanon, P. Drobinski and S. Fatichi, 2016 modifié en 2021. "Modification of land atmosphere interactions by CO2 effects: Implications for summer dryness and heat wave amplitude." Geophysical Research Letters 43(19): 10240-10248. Doi: 10.1002/2016GL069896. 

> Ay, J. S., J. Guillemot, N. Martin-StPaul, L. Doyen and P. Leanly, 2017. "The economics of land use reveals a selection bias in tree species distribution models." Global Ecology and Biogeography 26(1): 65 77.8. https://doi.org/10.1111/geb.12514. Résumé: "Aims: In human-dominated ecosystems, the presence of a given species is the result of both the ecological suitability of the site and human impacts such as land-use choices. The influence of land-use choices on the predictions of species distribution models (SDMs) has, however, been often neglected. Here, we provide a theoretical analysis of the land-use selection bias affecting classical SDMs in the case of either presence-only or presence–absence datasets. Land-use selection bias in the predictions of SDMs is then quantified for four widespread European tree species. Location: Continental France. Methods: We describe a bivariate selection model (BSM) that estimates simultaneously the economics of land-use choices and species responses to bioclimatic variables. The land-use equation, based on an econometric model of landowner choices, is joined to an equation of species responses to bioclimatic variables. Results: We found a significant land-use selection bias in all the species studied. The sign and the magnitude of the bias varied among species and were strongly related to the type of dataset used in the SDM calibration (presence-only or presence–absence). In addition, the BSM estimates the spatial covariance between the probability of presence and the presence of compatible land use. We found that, depending on the species, sites with high ecological suitability could present a high probability of compatible land use (positive covariance) or a low probability (negative covariance). Main conclusion: We showed that the use of classical SDMs in human-dominated areas can lead to strong miss-estimations of actual species distributions and could therefore prevents sound projections of the effects of climate change. The proposed BSM represents a crucial step to account for the economic forces shaping species distribution in anthropized areas and paves the way for a direct assessment of trade-offs and opportunities that may arise in a context of global change."

> Stéfanon, M., N. K. Martin-StPaul, P. Leadley, S. Bastin, A. Dell’Aquila, P. Drobinski and C. Gallardo, 2015. "Testing climate models using an impact model: what are the advantages?" Climatic Change 131(4): 649-661. Doi: 10.1007/s10584-015-1412-4

> Stéfanon, M., S. Schindler, P. Drobinski, N. de Noblet-Ducoudre and F. D'Andrea, 2014. "Simulating the effect of anthropogenic vegetation land cover on heatwave temperatures over central France." Climate Research 60(2): 133-146. Résumé: "Events similar to the 2003 heatwaves in France are likely to become more frequent, more intense and longer by the end of the 21st century. Policies for climate mitigation focus on carbon sequestration techniques while land cover change (LCC) may be a better short-term alternative at regional level. However, LCC impact studies conducted so far have often given contradictory results at mid-latitudes for summer temperature. Using a regional climate model, the impact of an afforestation scenario is evaluated for the years 2002 and 2003, and compared to an agricultural scenario. The favorable meteorological conditions in spring 2003 promote the development of agricultural vegetation compared to (1) conditions in 2002 and (2) tree phenology in the forested scenario. This dampens the extreme values of temperature from April to the end of June 2003 (up to 3°C during the June heatwave). From early July to October, drought conditions cause crop failure, while forests are not affected by the lack of soil moisture owing to a deeper root system. Evapotranspiration is therefore smaller in the agricultural scenario, thus amplifying the July−August extreme temperatures. However this cooling capacity of trees in the afforestation scenario is lim-ited during the August heatwave because the high temperatures reach a critical level above which the stomata close and transpiration is inhibited. Our experimental set-up highlights the role of climate−vegetation interactions during extreme events and demonstrates how choices of vegetation cover (e.g. trees versus crops) may substantially modify the summer temperatures in mid-latitude regions."

(Extrait de l'article susmentionné)

Communication orale

Lemordant, L., P. Gentine, M. Stefanon, P. Drobinski and S. Fatichi, Modification of land atmosphere interactions by CO2 effects: Implications for summer dryness and heat wave amplitude, AGU. Résumé: "Plant stomata couple the energy, water and carbon cycles. We use the framework of Regional Climate Modeling to simulate the 2003 European heat wave and assess how higher levels of surface CO2 may affect such an extreme event through land- atmosphere interactions. Increased CO2 modifies the seasonality of the water cycle through stomatal regulation and increased leaf area. As a result, the water saved during the growing season through higher water use efficiency mitigates summer dryness and the heat wave impact. Land-atmosphere interactions and CO2 fertilization together synergistically contribute to increased summer transpiration. This, in turn, alters the surface energy budget and decreases sensible heat flux, mitigating air temperature rise. Accurate representation of the response to higher CO2 levels, and of the coupling between the carbon and water cycles are therefore critical to forecasting seasonal climate, water cycle dynamics and to enhance the accuracy of extreme event prediction under future climate."

(extrait du poster susmentionné)