Our Common Future Under Climate Change

International Scientific Conference 7-10 JULY 2015 Paris, France

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Wednesday 8 July - 17:30-19:00 UPMC Jussieu - ROOM 107 - Block 24/34

1111 - Climate variability, change and vulnerability in the Pacific, Indian and Southern Oceans

Parallel Session

Chair(s): B. Pelletier (Grand Observatoire du Pacifique Sud GOPS, Nouméa, New Caledonia)

Lead Convener(s): E. Guilyardi (LOCEAN/IPSL, Paris, France)

Convener(s): V. Sarma (National Institute of Oceanography, Visakhapatnam, India), J.B. Sallée (Sorbonne Universités, Paris, France), M. Collins (Exeter University, Exeter, United Kingdom), M. Levy (UPMC, Paris, France), V. David (IRD, Nouméa, New Caledonia), D. Bakker (University of East Anglia, Norwich, United Kingdom)

17:30

Why should coral reefs care about ocean acidification: general consensus, misconceptions and future research priorities

R. Rodolfo-Metalpa (Institut de Recherche pour le Développement, Nouméa cedex, New Caledonia), F. Houlbrèque (Institut de Recherche pour le Développement, Nouméa cedex, New Caledonia), C. Payri (Institut de Recherche pour le Développement, Nouméa cedex, New Caledonia)

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Why should coral reefs care about ocean acidification: general consensus, misconceptions and future research priorities

R. Rodolfo-Metalpa (1) ; F. Houlbrèque (1) ; C. Payri (1)
(1) Institut de Recherche pour le Développement, Umr entropie-laboratoire d’excellence corail, Nouméa cedex, New Caledonia

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Ocean acidification (OA) is one of the main threats for marine habitats, likely causing changes in biodiversity and ecosystem functions within this century. Ocean acidification might affect various physiological parameters at different stages of the animal life history, from their reproduction to larval phases and adult growth. Coral reefs, harboring a large part of the world’s ocean biodiversity, will be the most affected by OA, as reef calcification and dissolution rates are related to seawater carbonate chemistry. Studies show a decline in net calcification rates as a result of decreasing pH and carbonate ion concentrations, and increasing dissolution rates of carbonate skeletons. This alarming general consensus has convinced the scientific community to deeply investigate marine ecosystems face to climate change, becoming among the top global ocean research priorities. After more than a decade studying OA responses of single species, mostly acclimated for short-time periods in laboratory conditions to projected acidified levels, it is time to progress our knowledge by better projecting ecological impacts of future climate change scenarios.

Recent findings show that some calcifiers do not seem to be affected by OA. Not only were their responses highly species-specific but varied among experiments. These divergent results have clearly shown that our actual knowledge on biological responses to OA and the physiological mechanisms involved are extremely limited and that some assumptions we have used so far might be inaccurate. In addition to these gaps of knowledge, all the data collected so far are single species responses to artificial conditions. Only few studies have scaled-up single species responses to the ecosystem scale. In our study, we aim at deciphering past misconceptions on the effects of OA, and promoting challenging research priorities in the field. This includes: i) to simultaneously test OA with other global environmental alterations, such as warming and eutrophication, which will likely exacerbate the organism’s sensitivity to OA; ii) to perform experiments in natural conditions, over longer periods, to guarantee at least a complete acclimation of organisms to natural variations. This requires a rapid implementation of in situ experimental systems able to change and to maintain suitable altered conditions; iii) to investigate keystone species/habitats potential abilities to adapt fast enough to environmental changes in order to guarantee vital ecosystem functions in the future. The best way to do that is through the use of sites naturally enriched in CO2 which have successfully been used as natural laboratories to study natural response of ecosystems to OA.

17:45

Bangladesh's coastal vulnerability under climate change

M. Becker (IRD, Toulouse, France), F. Papa (Institut de Recherche pour le Developpement, Toulouse, France), S. Calmant, (IRD, Toulouse, France), V. Ballu (CNRS/University of La Rochelle, La Rochelle, France), P. Valty (IGN, Paris, France), M. Karpytchev (Université de La Rochelle, La Rochelle, France), L. Testut (LEGOS/LIENSs, Toulouse, France), F. Hossain (University of Washington, Seattle, United States of America), C. Shum (Ohio State U./School of Earth Sci., Colombus, United States of America), A. Liibusk (Ohio State U./School of Earth Sci., Colombus, United States of America), S. Ouillon (IRD, Toulouse, France)

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Bangladesh's coastal vulnerability under climate change

M. Becker (1) ; F. Papa (2) ; S. Calmant, (1) ; V. Ballu (3) ; P. Valty (4) ; M. Karpytchev (5) ; L. Testut (6) ; F. Hossain (7) ; C. Shum (8) ; A. Liibusk (8) ; S. Ouillon (1)
(1) IRD, LEGOS, Toulouse, France; (2) Institut de Recherche pour le Developpement, LEGOS France and IFCWS, IISc India, Toulouse, France; (3) CNRS/University of La Rochelle, LIENSs, La Rochelle, France; (4) IGN, Lareg, Paris, France; (5) Université de La Rochelle, Lienss, La Rochelle, France; (6) LEGOS/LIENSs, Toulouse, France; (7) University of Washington, Dept. of civil & environmental engineering, Seattle, United States of America; (8) Ohio State U./School of Earth Sci., Div. of geodetic science, Colombus, United States of America

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In Bangladesh, the Ganges, Brahmaputra, and Meghna Rivers come together to form the largest river delta in the world. This low-lying region of the Bay of Bengal is one of the most densely populated countries in the world and is prone to monsoonal flooding, potentially aggravated by an intense annual cyclonic activity. In this context, sea-level rise, along with tectonic, sediment load and groundwater extraction induced land uplift/subsidence, significantly exacerbate the Bangladesh’s coastal vulnerability. Here we present the goals and first results of a Belmont Forum/IGFA-funded project, BanD-AID (http://Belmont-SeaLevel.org) that addresses the causes and consequences of coastal vulnerability of Bangladesh, The project's outcome will establish an advanced observation system based on contemporary space geodetic sensors to quantify (1) causes of sea-level rise and land motion and establish their robust vertical datum link, and (2) human interactions that governs coastal vulnerability and resilience in Bangladesh. We present the first results such as the apparent sea level rise at the Bangladesh coast gained by combining space geodetic observations, including satellite altimetry, GRACE and GPS/InSAR, together with in-situ tidal and river gauges, and different reconstructed sea-level approaches. This unique combination of different satellite techniques and in-situ information offers the possibility to better quantify the major contributions to the relative sea-level rise at the Bangladesh delta, towards addressing its coastal vulnerability and future sustainability.

18:00

Coastal vulnerability to climate change-induced sea-level rise may be increased by land motion and human factors

V. Ballu (CNRS/University of La Rochelle, La Rochelle, France), S. Calmant, (IRD, Toulouse, France), J. Aucan (IRD, Nouméa, New Caledonia), V. Duvat-Magnan (UMR LIENSs 7266 University of La Rochelle - National Centre for Scientific Research (CNRS), La Rochelle, France), B. Pelletier (Grand Observatoire du Pacifique Sud GOPS, Nouméa, New Caledonia), M. Becker (IRD, Toulouse, France), M. Gravelle (CNRS/Université de La Rochelle, La Rochelle, France), M. Karpytchev (Université de La Rochelle, La Rochelle, France), P. Valty (IGN, Paris, France), L. Testut (LEGOS/LIENSs, Toulouse, France), C. Shum (Ohio State U./School of Earth Sci., Colombus, United States of America), F. Hossain (University of Washington, Seattle, United States of America), Z. Khan (IWM, Dhaka, Bangladesh), P. Simeoni (Geo-consulte, Port-Vila, Vanuatu), T. Kanas (Land Survey, Port-Vila, Vanuatu)

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Coastal vulnerability to climate change-induced sea-level rise may be increased by land motion and human factors

V. Ballu (1) ; J. Aucan (2) ; V. Duvat-Magnan (3) ; B. Pelletier (4) ; M. Gravelle (5) ; C. Shum (6) ; M. Karpytchev (7) ; M. Becker (8) ; F. Hossain (9) ; P. Simeoni (10) ; P. Valty (11) ; S. Calmant, (8) ; Z. Khan (12) ; T. Kanas (13) ; L. Testut (14)
(1) CNRS/University of La Rochelle, LIENSs, La Rochelle, France; (2) IRD, Legos, Nouméa, New Caledonia; (3) UMR LIENSs 7266 University of La Rochelle - National Centre for Scientific Research (CNRS), Geography, La Rochelle, France; (4) Grand Observatoire du Pacifique Sud GOPS, Nouméa, New Caledonia; (5) CNRS/Université de La Rochelle, Lienss, La Rochelle, France; (6) Ohio State U./School of Earth Sci., Div. of geodetic science, Colombus, United States of America; (7) Université de La Rochelle, Lienss, La Rochelle, France; (8) IRD, LEGOS, Toulouse, France; (9) University of Washington, Dept. of civil & environmental engineering, Seattle, United States of America; (10) Geo-consulte, Port-Vila, Vanuatu; (11) IGN, Lareg, Paris, France; (12) IWM, Dhaka, Bangladesh; (13) Land Survey, Port-Vila, Vanuatu; (14) LEGOS/LIENSs, Toulouse, France

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Sea-level rise has been recognized as a major source of coastal vulnerability. Several areas, including low-lying Pacific islands and low lying countries such as Kiribati, Tuvalu, Marshall Islands and Bangladesh have been identified as being highly vulnerable to the effects of sea-level rise. While the major global source of sea-level rise is climate change, several other local factors can have as strong or stronger an effect than climate-based sea-level rise on coastal vulnerability.

We will present several case studies illustrating situations where increased coastal vulnerability is not solely attributed to climate change. We describe several other factors that can enhance the relative sea-level rise, such as natural factors like tectonic motions, erosion, sediment loading and local sea-level variability, and human factors like poorly designed development. Illustrating these factors using examples from Kiribati, Vanuatu, New Caledonia and Bangladesh, we emphasize that although climate related sea-level rise is a global issue, it can be locally combined with several other factors, modulating its value and impact. Studies of each individual case at the local scale are mandatory for adequate prediction and mitigation in the future.

18:15

Influence of climate changes on mangrove ability to fix and store CO2

C. Marchand (Institut de Recherche pour le développement (IRD), Paris, France), T. Meziane, (MNHN, Paris, France), M. Allenbach (University of new caledonia, Noumea, New Caledonia), A. Leopold, (University of New Caledonia, Noumea, New Caledonia), T. T. Nhutrang (University of Sciences, VNU, Ho Chi Minh City, Vietnam), A. Alfaro (University of Technology of Auckland, Auckland, New Zealand)

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Influence of climate changes on mangrove ability to fix and store CO2

C. Marchand (1) ; T. Meziane, (2) ; M. Allenbach (3) ; A. Leopold, (3) ; TT. Nhutrang (4) ; A. Alfaro (5)
(1) Institut de Recherche pour le développement (IRD), Paris, France; (2) MNHN, Paris, France; (3) University of new caledonia, Noumea, New Caledonia; (4) University of Sciences, VNU, Ho Chi Minh City, Vietnam; (5) University of Technology of Auckland, Auckland, New Zealand

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Mangroves are forested ecosystems developing in the intertidal zone of tropical and subtropical coastlines. They cover up to 140,000 km² worldwide, and extend from 30°N to 38°S (1). They are amongst the most productive ecosystems in the world (2). Furthermore, they have been suggested to be enhancers of heterotrophic secondary production and offshore fisheries. In addition, it is well recognized that tropical mangrove ecosystems provide a high abundance of food, shelter, and breeding and nursery habitats for a diverse community of terrestrial, aquatic and aerial organisms, including many endangered species (3). At a larger scale, the high net primary productivity of mangroves and low decomposition rates  results in global atmospheric CO2 sinks (4). In addition, mangroves are crucially important ecologically and economically, supporting a wide variety of ecosystem services (5). For example, mangroves stabilize the shoreline and serve as barriers against erosion. One of the most dramatic examples of the efficiency of this biological system as protection from catastrophic climatic events was demonstrated in 2004, when a large-scale tsunami devastate most coastal areas, but mangrove forested shorelines were significantly less affected (6). The annual economic value of mangroves, including products and services has been estimated to be US$ 200,000–900,000 ha-1 (7). Mangrove ecosystems have been decreasing dramatically worldwide, mainly due to habitat destruction. Once mangroves covered more than 200,000 km2 worldwide (8). However, human population growth and urbanization of coastal areas, expansion of industrial activities, and exploration and exploitation of natural resources have resulted in a current decrease in mangrove area of 1 to 2% per year. This declining rate is equivalent or even higher than that of other threatened ecosystems, such as coral reefs or primary rainforests (9). Mangrove ecosystems also are also threatened by climate change. However, the responses of mangrove ecosystems to climate changes are not well understood (10). Relative sea-level rise may be the greatest threat to mangroves because most mangrove sediment surface elevations are not keeping pace with sea-level rise (11). Additionally, the increases of temperature and atmospheric CO2 concentrations may also modify their functioning and distribution. Reduced mangrove area and health will increase the threat to human safety and shoreline development from coastal hazards, such as erosion, cyclonic events, and tsunamis (12). Mangrove habitat loss also may reduce coastal water quality, biodiversity, and fish and crustacean breeding and nursery habitats. Such ecological deterioration may have direct and indirect adverse effect on adjacent coastal habitats, and may eliminate a major resource for human communities that rely on mangroves for numerous products and services. Mangrove destruction also has the potential to release large quantities of stored carbon, which can have dramatic global implications (13). A synthesis of the current knowledge will be proposed, and our project of mangrove monitoring in the Indo-pacific area will be presented.

1. Giri et al., 2011. Status and distribution of mangrove forests... Global Ecology and Biogeography 20, 154-159 /2. Bouillon et al.. 2008. Mangrove production and carbon sinks... Global Biogeochemical Cycling 22, GB 2013 /3. Nagelkerken et al. 2008. The habitat function of mangroves... Aquat. Bot. 89, 155–185 /4. Donato et al., 2011. Mangroves among the most carbon-rich forests... Nature Geoscience 4, 293-297 /5. Barbier, 2007. Valuing ecosystem services... Economic Policy 22:177–229 /6. Walters et al. 2008. Ethnobiology, socioeconomics and management of mangrove forests... Aquat. Bot. 89, 220–236 /7. Wells et al., 2006.  Shoreline Protection... UN Environment Programme World Conservation Monitoring Centre, 33 pp /8. Spalding et al.., 1997. World Mangrove Atlas, International Society for Mangrove Ecosystems, Japan /9. Duke, et al. 2007. A world without mangroves? Science 317, 41–42 /10. Gilman et al.., 2008. Threats to mangroves from climate change... Aquat. Bot. 89, 237-250 /11. Lovelock, C.E., Ellison, J.C., 2007. Vulnerability of mangroves ... In: Climate Change and the Great Barrier Reef: A Vulnerability Assessment. pp. 237-269 /12. Danielsen et al., 2005. The asian tsunami... Science 310, 643 /13. Kristensen et al., 2008 Organic carbon dynamics in mangrove ecosystems...Aquat. Bot. 89, 201-219.

18:30

Evolution of dengue epidemics in the south pacific in the present and the future

C. Menkes (IRD, Noumea, New Caledonia), M. Mangeas (IRD, Montpellier, France), M. Teurlai (IRD, Noumea, New Caledonia), V. Cavarero (Météo-France , Noumea, New Caledonia), M. Daures (DDASS, Noumea, New Caledonia), E. Descloux (Territorial Hospital Centre, Noumea, New Caledonia), N. Degallier (IRD, Noumea, New Caledonia), L. Guillaumot (Institut Pasteur de Nouvelle Calédonie, Noumea, New Caledonia), J.-P. Grangeon (DDASS, Noumea, New Caledonia), F. Mathieu-Daudé (IRD, Noumea, New Caledonia), M. Lengaigne (UPMC, Paris, France), A. Mercier (IRD, Noumea, New Caledonia), M. Dupont-Rouzeyrol (Institut Pasteur de Nouvelle Calédonie, Noumea, New Caledonia), S. Hales (University of Otago, Wellington, New Zealand), L. Mciver (National Centre for Epidemiology and Population Health, Canberra, Australia), J. Benzler (Robert Koch Institute, Berlin, Germany), V.-M. Cao-Lormeau (Institut Louis Mallardé, Papeete, French Polynesia), C. Dutheil, (IRD, Noumea, New Caledonia)

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Evolution of dengue epidemics in the south pacific in the present and the future

C. Menkes (1) ; M. Mangeas (2) ; M. Teurlai (3) ; V. Cavarero (4) ; M. Daures (5) ; E. Descloux (6) ; N. Degallier (1) ; L. Guillaumot (7) ; JP. Grangeon (5) ; F. Mathieu-Daudé (8) ; M. Lengaigne (9) ; A. Mercier (1) ; M. Dupont-Rouzeyrol (7) ; S. Hales (10) ; L. Mciver (11) ; J. Benzler (12) ; VM. Cao-Lormeau (13) ; C. Dutheil, (1)
(1) IRD, LOCEAN, Noumea, New Caledonia; (2) IRD, Espace-dev, Montpellier, France; (3) IRD, Locean/espace-dev, Noumea, New Caledonia; (4) Météo-France , Noumea, New Caledonia; (5) DDASS, Noumea, New Caledonia; (6) Territorial Hospital Centre, Noumea, New Caledonia; (7) Institut Pasteur de Nouvelle Calédonie, Noumea, New Caledonia; (8) IRD, Mivegec, Noumea, New Caledonia; (9) UPMC, Paris, France; (10) University of Otago, Wellington, New Zealand; (11) National Centre for Epidemiology and Population Health, Australian national university, Canberra, Australia; (12) Robert Koch Institute, Berlin, Germany; (13) Institut Louis Mallardé, Papeete, French Polynesia

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Dengue fever is the most important mosquito-borne viral disease, with 390 million people being infected each year and 2.5 billion people living in areas at risk of dengue worldwide. The rapid global spatial spread over the past 40 years is likely to be due to recent socio-economic changes such as global population growth and uncontrolled urbanisation but these factors need to be associated with suitable climatic conditions before dengue fever can establish itself in a given country, for it is transmitted by a number of mosquito species, mainly Aedes aegypti, whose life cycle is influenced by temperature, rainfall and humidity. In the following contribution, we focus on the South Pacific region, a vast, oceanic region where dengue epidemics are recurrent, aiming at disentangling socio-economic factors from climate factors.

We first analyse an original dengue database covering the 1971-2009 period across the South Pacific. In the Pacific region, dengue epidemics occurred every 3 to 6 years, with each epidemic wave caused by the regional circulation of 1 of the 4 dengue virus serotypes, with very limited serotype co-circulation. There are no apparent spatial propagation patterns in the region, and countries such as French Polynesia and New Caledonia are the most regularly affected. There is a weak anti-correlation between the major El Niño climate variability and the annual number of countries experiencing an epidemic, suggesting a link between climate and dengue epidemics. However, while the South Pacific has experienced a weak + 0.5°C trend in temperature, there is no detectable overall/regional long-term trend in the evolution of the number of affected countries for the past 40 years. However, local trends exist: New Caledonia is experiencing a positive trend whereas dengue epidemic frequency is decreasing in some smaller islands. We then analyse dengue epidemic profiles per country (endemic, regular epidemics, or sporadic epidemics). We identify variables linked to the different profiles by fitting a statistical model based on variables characterizing the socio-economic situation (e.g. GDP) or climate (e.g. temperature) in each country. These statistical models are able to reproduce the major epidemic profiles. Assuming the socio-economic variables to remain constant over time, we project these models for the next 100 years using models of the IPCC-AR5 under RCP8.5.

Finally, we focus on the case of New Caledonia where very high quality data allows a more quantitative analysis. At present, dengue epidemics there occur approximately every 6 years. Using spatial statistical modelling, we show that the primary variables explaining the spatial distribution of incidence rates are the mean temperature and a variable highly correlated with people's way of life. Using this model, we show that by the end the 21st century, with temperature increasing by approximately 3°C as projected by 6 IPCC-AR5 models in New Caledonia, mean incidence rates will be multiplied by two, with areas currently at low risk of dengue fever being highly exposed in the future. In terms of dengue epidemics recurrences, we also build a temporally dynamic model at weekly time scales allowing the detection of the beginning and length of dengue epidemics. One key variable is the number of days where temperature exceeds 32 °C. As this number will increase substantially over the next 100 years in the IPCC-AR5 models, we show that the proportion of dengue epidemic years will rise from 17 % at present to 100 % in the RCP8.5 scenario and 66 % in the RCP4.5 scenario, with the duration of dengue epidemics substantially increasing compared to the present day. Implications for the future of dengue virus circulation in the South Pacific are discussed on the basis of our results.

18:45

Discussion

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Discussion
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