Quelles stratégies d'adaptation aux changements globaux (climat) pour les forêts du Sud Ouest de l'Europe?

Intitulé et acronyme du projet: Évaluation des processus, méthodes et variables pour la Méditerranéisation potentielle des socio-écosystèmes en Europe occidentale - Tplus3

Financé dans le cadre de l'Appel à projet blanc 2014, le projet Tplus3 s'est déroulé sur 2 ans (2015-2016). 

Porteurs du projet : Juan FERNANDEZ (ESE) et Stephane Dupas (EGCE)

Partenaires

• dans BASC: CIRED        
• académiques hors BASC : LMD Ecole Polytechnique, Instituto Pirenaico de Ecología (Spain), Universidad de Alcala de Henares, AgroClim (INRA Avignon), BIOGECO (INRA Bordeaux), Universidade Tecnica de Lisboa

L'une des plus grandes difficultés pour étudier l'impact des changements globaux des systèmes socio-écologiques est qu'il n'existe que très peu de consensus sur les questions, les méthodes et les disciplines requises pour traiter ces problèmes. L'objectif de cette proposition est de créer un réseau de chercheurs du Portugal, d'Espagne et de France afin d'identifier les principaux processus, méthodes et variables nécessaires pour aborder la dynamique des changements socio-écologiques dans les zones de transition entre les régions méditerranéennes et tempérées d'Europe occidentale sous l'influence des changements mondiaux.

En partant d'un groupe "central" composé d'un écologiste végétal, d'un modélisateur en biologie des populations, d'un climatologue et d'un économiste, une série de 4 ateliers d'une journée par an (à 3 mois d'intervalle) sera mise en place avec des chercheurs locaux et invités afin d'avancer conceptuellement vers le développement d'une méthodologie commune. Cette série d'ateliers d'une journée sera précédée d'une réunion de lancement pour identifier les participants clés. Entre les ateliers, les participants se verront confier des tâches visant à synthétiser/proposer les méthodologies nécessaires pour aborder les études de la dynamique des socio-écosystèmes dans le cadre du changement global.

Outre la construction d'un réseau solide prêt à demander des subventions plus importantes, il est prévu qu'un document conceptuel/méthodologique novateur émerge à la fin de la période.

Résultats

Tplus3 is a network project that aimed at identifying adaptation strategies to global changes at the local scale by looking at the socio-ecological transects that exist between Mediterrenean and Temperate areas in Western Europe. Social-ecological systems (SES) occurring along climatic gradients can provide real examples of how local adaptations to global processes like climate change can be made. We examined forest social-ecological systems in temperate European where the potential spread of dry Mediterranean-like conditions may induce not only vegetation changes but the ways people relate to ecosystems. Models in this area predict widespread increases of evergreen and xeric vegetation with potential increases in fire risks. Moreover, current demographic trends of rural land abandonment can increase the levels of fire risk if biomass is left to accumulate unattended under warmer and drier climates. While open husbandry and agroforestry may provide new opportunities preventing fires in temperate areas, low diversity fuel-wood plantations, local knowledge loss, and emerging diseases on keystone species may hamper the adaptation process to climate change. Policymakers can use observations along gradients to make adaptations proactively, combining solutions that would otherwise be difficult to identify.

Publication

> Fernández-Manjarrés J. F., Ruiz-Benito P., Zavala M., Camarero J. J., Pulido F., Proença V., Navarro L., Sansilvestri R., Granda E., Marqués L., Temunovič M., Bertelsmeier C., Drobinski P., Roturier S., Benito-Garzón M., Cortazar-Atauri I. G., Simon L., Dupas S., Levrel H., Sautier M. (2018). Forest  Adaptation to Climate Change along Steep Ecological Gradients: The Case of the Mediterranean-Temperate Transition in South-Western Europe. Sustainability 10, no. 9: 3065. doi:10.3390/su10093065. Résumé: "Impacts of climate change are likely to be marked in areas with steep climatic transitions. Species turnover, spread of invasive species, altered productivity, and modified processes such as fire regimes can all spread rapidly along ecotones, which challenge the current paradigms of ecosystem management. We conducted a literature review at a continental-wide scale of South-Western European forests, where the drier and warmer conditions of the Mediterranean have been widely used as examples of what is expected in more temperate areas. Results from the literature point to: (a) an expansion of slow-growing evergreen hardwood trees; (b) increased dieback and mortality episodes in forests (both natural and planted) mostly related to competition and droughts, and mainly affecting conifers; and (c) an increase in emergent diseases and pests of keystone-trees used in agroforestry zones. There is no consensus in the literature that fire regimes are directly increasing due to climate change, but available satellite data of fire intensity in the last 17 years has been lower in zones where agroforestry practices are dominant compared to unmanaged forests. In contrast, there is agreement in the literature that the current spread of fire events is probably related to land abandonment patterns. The practice of agroforestry, common in all Mediterranean countries, emerges as a frequent recommendation in the literature to cope with drought, reduce fire risk, and maintain biodiverse landscapes and rural jobs. However, it is unknown the extent to which the open vegetation resulting from agroforestry is of interest to forest managers in temperate areas used to exploiting closed forest vegetation. Hence, many transitional areas surrounding the Mediterranean Basin may be left unmanaged with potentially higher climate-change risks, which require active monitoring in order to understand and help ongoing natural adaptation processes."           Illustration: "Current observations of increasing evergreen tree density in the study area in South-Western Europe (black triangles)."