Changement climatique et biosphère

International audienceClimate change has become the third cause of biodiversity loss behind the exploitation of natural environments by humans and direct exploitation (food, health, raw materials). It could become the primary cause of biodiversity loss by the next century. Climate change has modified the biological rhythms and distributions of species, the functioning of ecosystems, trophic chains, biogeochemical cycles, and ecosystem services. The projections that we are able to provide of the future evolution of the biosphere show an amplification of the phenomena observed the last fifty years. Species have very limited ways to adapt given the speed at which climate change occurs. This is why, beyond reducing greenhouse gas emissions, it is also necessary to reduce the other anthropogenic pressures on the biosphere.Le changement climatique est devenu la troisième cause de perte de biodiversité derrière l’exploitation des milieux naturels par l’homme et les prélèvements directs (alimentation, santé, matières premières). Il pourrait devenir la première cause de perte de biodiversité d’ici le siècle prochain. Le changement climatique a modifié les rythmes biologiques et les aires de répartition des espèces, le fonctionnement des écosystèmes, les chaînes trophiques, les cycles biogéochimiques, et les services écosystémiques. Les projections que nous sommes capables de fournir de l’évolution future de la biosphère montrent une amplification des phénomènes observés depuis cinquante ans. Les moyens d’adaptation du vivant sont très limités étant donné la vitesse à laquelle se produit le changement climatique. C’est pourquoi, il est nécessaire, au-delà de la réduction des émissions de gaz à effet de serre, de réduire également les autres pressions anthropiques sur la biosphère

Changement climatique et biosphère

Climate change has become the third cause of biodiversity loss behind the exploitation of natural environments by humans and direct exploitation (food, health, raw materials). It could become the primary cause of biodiversity loss by the next century. Climate change has modified the biological rhythms and distributions of species, the functioning of ecosystems, trophic chains, biogeochemical cycles, and ecosystem services. The projections that we are able to provide of the future evolution of the biosphere show an amplification of the phenomena observed the last fifty years. Species have very limited ways to adapt given the speed at which climate change occurs. This is why, beyond reducing greenhouse gas emissions, it is also necessary to reduce the other anthropogenic pressures on the biosphere

How can model comparison help improving species distribution models?

Today, more than ever, robust projections of potential species range shifts are needed to anticipate and mitigate the impacts of climate change on biodiversity and ecosystem services. Such projections are so far provided almost exclusively by correlative species distribution models (correlative SDMs). However, concerns regarding the reliability of their predictive power are growing and several authors call for the development of process-based SDMs. Still, each of these methods presents strengths and weakness which have to be estimated if they are to be reliably used by decision makers. In this study we compare projections of three different SDMs (STASH, LPJ and PHENOFIT) that lie in the continuum between correlative models and process-based models for the current distribution of three major European tree species, Fagus sylvatica L., Quercus robur L. and Pinus sylvestris L. We compare the consistency of the model simulations using an innovative comparison map profile method, integrating local and multi-scale comparisons. The three models simulate relatively accurately the current distribution of the three species. The process-based model performs almost as well as the correlative model, although parameters of the former are not fitted to the observed species distributions. According to our simulations, species range limits are triggered, at the European scale, by establishment and survival through processes primarily related to phenology and resistance to abiotic stress rather than to growth efficiency. The accuracy of projections of the hybrid and process-based model could however be improved by integrating a more realistic representation of the species resistance to water stress for instance, advocating for pursuing efforts to understand and formulate explicitly the impact of climatic conditions and variations on these processes

Where is the optimum? Predicting the variation of selection along climatic gradients and the adaptive value of plasticity. A case study on tree phenology

International audienceMany theoretical models predict when genetic evolution and phenotypic plasticity allow adaptation to changing environmental conditions. These models generally assume stabilizing selection around some optimal phenotype. We however often ignore how optimal phenotypes change with the environment, which limit our understanding of the adaptive value of phenotypic plasticity. Here, we propose an approach based on our knowledge of the causal relationships between climate, adaptive traits, and fitness to further these questions. This approach relies on a sensitivity analysis of the process-based model Phenofit, which mathematically formalizes these causal relationships, to predict fitness landscapes and optimal budburst dates along elevation gradients in three major European tree species. Variation in the overall shape of the fitness landscape and resulting directional selection gradients were found to be mainly driven by temperature variation. The optimal budburst date was delayed with elevation, while the range of dates allowing high fitness narrowed and the maximal fitness at the optimum decreased. We also found that the plasticity of the budburst date should allow tracking the spatial variation in the optimal date, but with variable mismatch depending on the species, ranging from negligible mismatch in fir, moderate in beech, to large in oak. Phenotypic plasticity would therefore be more adaptive in fir and beech than in oak. In all species, we predicted stronger directional selection for earlier budburst date at higher elevation. The weak selection on budburst date in fir should result in the evolution of negligible genetic divergence, while beech and oak would evolve counter-gradient variation, where genetic and environmental effects are in opposite directions. Our study suggests that theoretical models should consider how whole fitness landscapes change with the environment. The approach introduced here has the potential to be developed for other traits and species to explore how populations will adapt to climate change

L'écologie participative

National audienceLa préoccupation des citoyens à l'égard des problèmes environnementaux s'accroit d'année en année. Parmi ceux-ci, le changement climatique a tendance à prendre une part de plus en plus importante dans les débats publics, comme il prend de plus en plus d'importance dans la recherche publique. Les initiatives citoyennes pour promouvoir des activités humaines plus respectueuses de l'environnement se multiplient. La recherche publique se doit d'accompagner ces initiatives pour guider les citoyens vers les solutions les plus appropriées selon les contextes. La recherche participative en écologie peut représenter un des moyens d'accompagnement

Une course contre la montre pour protéger la biosphère

National audienceFace au changement climatique et à sa rapidité, les capacités d’adaptation du vivant, qui nous rend des services vitaux, sont dangereusement limitées. Isabelle Chuine nous explique comment ses recherches permettent d’anticiper ses conséquences, pour agir

L'écologie participative

National audienceLa préoccupation des citoyens à l'égard des problèmes environnementaux s'accroit d'année en année. Parmi ceux-ci, le changement climatique a tendance à prendre une part de plus en plus importante dans les débats publics, comme il prend de plus en plus d'importance dans la recherche publique. Les initiatives citoyennes pour promouvoir des activités humaines plus respectueuses de l'environnement se multiplient. La recherche publique se doit d'accompagner ces initiatives pour guider les citoyens vers les solutions les plus appropriées selon les contextes. La recherche participative en écologie peut représenter un des moyens d'accompagnement

Une course contre la montre pour protéger la biosphère

National audienceFace au changement climatique et à sa rapidité, les capacités d’adaptation du vivant, qui nous rend des services vitaux, sont dangereusement limitées. Isabelle Chuine nous explique comment ses recherches permettent d’anticiper ses conséquences, pour agir

Résilience de nos sociétés et de l'agriculture face à des crises : place de la biodiversité

National audienc