Our Common Future Under Climate Change

International Scientific Conference 7-10 JULY 2015 Paris, France

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Wednesday 8 July - 15:00-16:30 UPMC Jussieu - Amphi 24

2213 - Ecological feedbacks to climate change

Parallel Session

Lead Convener(s): L. Abbadie (Pierre & Marie Curie University, Paris, France), J.F. Silvain (Fondation pour la Recherche sur la Biodiversité, Paris, France)

Convener(s): G. Boeuf (National Museum of Natural History, Paris, France)

15:00

Responses of marine ecosystems to climate change and ocean acidification

W. Cheung (University of British Columbia, Vancouver, Canada)

Abstract details
Responses of marine ecosystems to climate change and ocean acidification

W. Cheung (1)
(1) University of British Columbia, Fisheries Centre, Vancouver, Canada

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Changes in temperature, oxygen level, acidity and other ocean properties directly affect marine ecosystems through shifts in biogeography, phenology, productivity and trophic interactions. This paper synthesizes our latest understanding on the extent to which climate change and ocean acidification are affecting global marine ecosystems structure, functions and services and the resulting vulnerability. As shown by analyzing global marine biogeography records and fisheries data, ocean warming has already been altering marine species assemblages in the past four decades. Moreover, mapping of vulnerability of almost 1000 species marine fishes in the global ocean based on their exposure to climate stressors and biological sensitivity and adaptive capacity indicates that most of the studied marine fishes become highly vulnerable to climate change under high greenhouse gas emission scenarios. Such findings corroborate with results from simulation modelling of global shifts in distributions of marine fishes and invertebrates, highlighting the large climate risks of regional ecosystems, particularly in the tropics, in terms of decreases in biodiversity and key ecosystem services such as fisheries. Scope of adaptation to these changes may not be sufficient to substantially reduce these risks, particularly in sensitive ecosystems. These evidence demonstrates the multi-facet responses of marine ecosystems to climate change, identify hotspots of vulnerable ocean regions to climate change, and highlights the need for ongoing interdisciplinary efforts between marine biologists, ecologists, oceanographers are needed to further reveal the multi-scales (spatial, temporal and organizational) responses of marine ecosystems to climate change, ocean acidification and interactions with other human stressors.

15:30

Ecological emergence of thermal clines in body size

E. Edeline (Institue of Ecology and Environmental Sciences, Paris, France), G. Lacroix (Institue of Ecology and Environmental Sciences, Paris, France), C. Delire (GAME/CNRM, CNRS/Météo-France, Paris, France), N. Poulet (French National Agency for Water and Aquatic Environments (ONEMA), Vincennes, France), S. Legendre (CNRS, UMR 7625 Ecologie & Evolution, Paris, France)

Abstract details
Ecological emergence of thermal clines in body size

E. Edeline (1) ; G. Lacroix (1) ; C. Delire (2) ; N. Poulet (3) ; S. Legendre (4)
(1) Institue of Ecology and Environmental Sciences, Paris, France; (2) GAME/CNRM, CNRS/Météo-France, Paris, France; (3) French National Agency for Water and Aquatic Environments (ONEMA), Vincennes, France; (4) CNRS, UMR 7625 Ecologie & Evolution, Paris, France

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The unprecedented rate of global warming requires a better understanding of how ecosystems will respond. Organisms often have smaller body sizes under warmer climates (Bergmann's rule and the temperature-size rule), and body size is a major determinant of life histories, demography, population size, nutrient turnover rate, and food-web structure. Therefore, by altering body sizes in whole communities, current warming can potentially disrupt ecosystem function and services. However, the underlying drivers of warming-induced body downsizing remain far from clear. Here, we show that thermal clines in body size are predicted from universal laws of ecology and metabolism, so that size-dependent selection from competition (both intra and interspecific) and predation favours smaller individuals under warmer conditions. We validate this prediction using 4.1 million individual body size measurements from French river fish spanning 29 years and 52 species. Our results suggest that warming-induced body downsizing is an emergent property of size-structured food webs, and highlight the need to consider trophic interactions when predicting biosphere reorganizations under global warming.

15:50

From cut twig to satellite – understanding the full response of phenology to climate change

A. Menzel (Technische Universität München, Freising, Germany)

Abstract details
From cut twig to satellite – understanding the full response of phenology to climate change

A. Menzel (1)
(1) Technische Universität München, Ecology and Ecosystem Management, Freising, Germany

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Phenology (the timing of seasonal natural events such as plant growth or animal migration) is now commonly used as indicator for evaluating responses of ecosystems to climate change. More than 500 papers are published annually that include ‘phenolog*’ in their title and many of them are related to anthropogenic change. Recent phenological changes have been reported across the globe, continents, ecosystems, habitats and taxa, predominantly as mean temporal changes (‘trends’) or as relationships to temperature and other drivers (‘responses’); they have been summarized in various meta-analyses as well as in the IPCC WG II contributions to the AR4 and AR5. Although it has been well known during the 20th century that phenological events are triggered predominantly by climate, it was only in the late 1990s that phenology emerged as a key asset in identifying fingerprints of climate change in natural systems, when significantly advancing spring events were identified on larger scales mirroring recent warming.

Since then, phenological research has made considerable advances but is now at a crossroads of understanding its full climate change response and associated variability. Especially, other drivers of phenology than forcing by spring temperature, such as chilling and photoperiod preventing too early spring development and thus damage by late spring frosts, precipitation, snow, nutrients, ambient CO2 concentration or management effects have come to the fore. In addition, more emphasis has been given on reproductive phases and autumn changes in the last decade. The reported variability in observed trends and responses has been related to geno- / phenotypes, microclimate in stands, provenances and origins, species, species traits and phylogeny, regional climates and methodological considerations.

The timing of leaf development strongly regulates earth-atmosphere interactions and thus climate feedbacks, e.g. via biogeochemical cycles and impacts on the global energy balance, as well as biotic processes, such as pollination, agricultural and forestry production, and human health (via allergenic pollen). Thus, a full explanatory understanding of phenological drivers, accurate predictions and development of adaptation options are emerging topics which also need a full acknowledgement of the observed variability in trends and responses. In data-intensive analyses of observations, the inherent variability may facilitate the correct identification of all drivers, whereas in novel experimental approaches, the observed variability may call for a higher number of species, treatments and replicates. Variability may yield to more plasticity and resilience to climate change and thus phenological responses will drive the fitness and adaptation capacities of species. In this review, I summarize the current knowledge and recent insights into observed changes in phenology from satellite data to multispecies records, describe observed spatio-temporal variability linked to species traits and regional climates and highlight the role of additional drivers other than spring climate recently derived from cut twigs. Only a full consideration of variation in these responses will allow a complete understanding of ecological, cultural and socioeconomic consequences of these phenological changes mirroring climate change, driving impacts in the biosphere and feeding back to the climate system.

16:10

Round table and general discussion with all speakers and poster authors

Abstract details
Round table and general discussion with all speakers and poster authors
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