Effets des activités de l homme sur l'environnement à l échelle de la planète

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1 UMR 8079 Effets des activités de l homme sur l'environnement à l échelle de la planète Paul LEADLEY Professor, ESE Laboratory, Université Paris-Sud 11 Laboratoire d Ecologie, Systématique et Evolution

2 Climate Change: Making the Case for Action Laboratoire d Ecologie, Systématique et Evolution

3 Key Scientific Elements of the Climate Change Case Laboratoire d Ecologie, Systématique et Evolution Document past and current changes in climate Develop models to describe earth s climate Compare models and data Generate quantitative estimates of future change and their uncertainties Estimate the costs of failing to act and of mitigation Communicate with public and decision makers Develop adaptive managment strategies (weak)

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7 If there is no action to control emissions, each tonne of CO 2 that we emit now is causing damage worth at least $85 There are many opportunities to cut emissions for less than $25 a tonne. According to one measure, the benefits over time of actions to shift the world onto a low-carbon path could be in the order of $2.5 trillion each year. In other words, reducing emissions will make us better off.

8 Impacts of Global Change on Ecosystems: The Millennium Assessment and the Biodiversity Example Laboratoire d Ecologie, Systématique et Evolution

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10 Historical patterns and current trends in biodiversity Laboratoire d Ecologie, Systématique et Evolution

11 Global terrestrial biodiversity projections from the Millennium Assessment Percent species loss MA scenarios species loss for Terrestrial biomes using 4 socioeconomic models

12 Global freshwater biodiversity projections from the Millennium Assessment MA scenarios of fish species loss in rivers with projected declining flow Laboratoire d Ecologie, Systématique et Evolution

13 Biodiversity and Ecosystem Services

14 A multi-regional study using bioclimatic models Thomas et al Nature Used species-based bioclimatic models for several regions plus species area relationships to predict the effects of climate change on biodiversity. "We predict, on the basis of midrange climate-warming scenarios that 15-37% of species... will be 'committed to extinction by the year 2050."

15 Impacts on Ecosystems and Adaptation: Sectorial and Regional Approaches Laboratoire d Ecologie, Systématique et Evolution

16 Rising CO 2 and climate change impacts on coral reefs 1) Rising CO 2 concentrations increase ocean acidity. This reduces the capacity of hard corals to build reefs 2) High temperatures cause reef polyps to loose their symbiotic relationship with algae ( bleaching ). 1) + 2) = very bad news for coral reefs Hoegh-Guldberg et al Science

17 Effects of rising atmospheric CO 2 on coral reefs Atmospheric CO 2 concentration Models of ocean chemistry suggest that hard corals will be unable to build reefs (aragonite) or that coral reefs may even begin to dissolve due to ocean acidification by the middle of the 21st Century Hoegh-Guldberg et al Science Level below which hard corals cannot build reefs

18 Climate change and rising CO 2 impacts on coral reefs Examples of what the future might look like (photos from the Great Barrier Reef) Healthy Coral reef Bleached coral reef = large areas already, most coral reefs in the next few decades Dead reef = middle to end of the 21st century Hoegh-Guldberg et al Science

19 Impacts of global change on ecosystem services of coral reefs and possible adaptive managment strategies Socio-Economic Impacts Tourism provides up to half the gross domestic product in some Caribbean basin countries - reefs are an important draw for tourists Coral reef fishing is a major source of income and food, Reefs provide protection against sea storm surges, etc. Action to Minimize Damage Reduce additional stressors - eutrophication, pollution with pesticides and herbicides, destructive fishing Restore ecosystem function - in particular, urchins play a critical role in maintaining healthy reefs Minimize atmospheric CO 2 increase Use active management (e.g., sun shades) to reduce temperature extremes in key areas

20 An example of the modeled impact of climate change on a key European tree species Arpège climate model - A2 + Nichebased distribution Current model distribution 2100 Fagus sylvatica Nancy NBM - Badeau et al. (2005)

21 Treating UNCERTAINTY in modeling climate impacts on forests: an example from the ANR QDiv project High resolution climate scenarios Collaboration with CERFACS (L. Terray) High resolution maps of current tree distributions Collaboration IFN (C. Cluzeau) High resolution maps of key soil properties A broad range of models of tree response to climate change Niche Based BIOMOD NANCY-NBM Phenology-based Assessment of climatic risk for: Quercus robur Quercus petraea Furnished by INRA Orléans PHENOFIT DGVM Orchidée IBIS Hybrid 2 Fagus sylvatica Pinus sylvestris E.g., Simulated mean August temperatures in 2098 E.g., current distribution of Fagus sylvatica (Common beach) Mechanistic Tree growth CASTANEA Gap Dynamics TreeMig Larix decidua Quercus ilex

22 Adaptation Laboratoire d Ecologie, Systématique et Evolution Focusing on the distribution and the health of key species or functional groups provides a clear means of communicating with natural resource managers and decision makers A manual of management techniques to limit climate change impacts on forests

23 Global change impacts on biodiversity and ecosystem services: making the case for action Researchers must improve the quality of their models of future global change impacts on biodiversity and ecosystem services (validation, assessment of uncertainty, mechanism) Researchers and natural resource managers must develop adaptive managment strategies that account for uncertainties in the drivers of global change and the responses of ecosystems to these drivers. The science-policy dialog concerning global change impacts on biodiversity and ecosystem services must be reinforced

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25 but there is a need for a science-policy-managment interface for global change impacts on biodiversity and ecosystem services Intergovernmental Platform on Biodiversity and Ecosystem Services (UNEP + IUCN + France)