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

Marchand, C., Meziane, T., Allenbach, M., Leopold, A.,

Nhu-Trang, T.T., Alfaro, A.

8th July 2015, CFCC, Paris cyril.marchand@ird.fr

Mangrove distribution (green) (source : WCMC, 1997)

- Forested ecosystems developing in the intertidal zone of tropical and subtropical coastlines, covering more than 136 760 km², and extending over

a latitudinal range of 30°N to 38°S

- Its vegetation is composed of ~19 families, made up to ~27 genera and ~70 species

- Since the beginning of Eocene (53 M yrs) / First fossil traces in the Mesozoic (240 M yrs)

A remarkable ecosystem

- Adaptation capacities to the extremely selective environment:

. Salinity (from 10 to 90)

. Anoxia

. Waterlogging

. Substrate instability, etc..

A remarkable ecosystem

- Role in the culture of the littoral communities

- Supplies the elementary needs / Fishing

- Stabilize the coastline /act as barrier against the erosion

- Base of the nutrient cycling in coastal environment

- Shelter a big animal biodiversity / Significant refuge value

- Biofilter

Highly productive ecosystem (149 mol C m-2 y-1)

Litter fall

Wood production

Root production

water-atmosphere

CO2 efflux

Exchange

of POC, DOC

and DIC

sediment

burial

sediment-atmosphere

and sediment-water

CO2 exchange

Faunal assimilaton

and respiration

- Kristensen E., Bouillon, S., Dittmar, T., Marchand, C. 2008. Organic carbon dynamics in mangrove ecosystem, a review. Aquatic Botany 89, 201-219.

- Bouillon, S., Borges, A. V., Castañeda-Moya, E., Diele, K., Dittmar, T., Duke, N. C., Kristensen, E., Lee, S. Y., Marchand, C., Middelburg, J. J., Rivera-Monroy, V. H., Smith III, T.J., and Twilley, R. R. 2008. Mangrove production and carbon sinks: a revision of global budget estimates. Global Biogeochemical Cycling 22, GB 2013.

- Lee, S.Y., Primavera, J.H., Dahdouh-Guebas, F., McKee, K., Bosire, J.O., Cannicci, S., Diele, K., Fromard, F., Koedam, N., Marchand, C., Mendelssohn, I., Mukherjee, N., Record, S. (2014). Redefining the ecological role and services of tropical mangrove ecosystems. Journal of Global Ecology and Biogeography

CO2 CO2

Mangrove = Sink for atm CO2

Role in carbon cycling

-Because of their high productivity and the anoxic character of their soils, mangroves are interesting carbon sink

-Such coastal vegetation sequesters carbon far more effectively (up to 100 times faster) and more permanently than terrestrial forests.

(Alongi, 2009; Bouillon et al., 2008; Chmura et al., 2003; Donato et al., 2011; 2012; Kauffman et al., 2011; Ray et al., 2011)

Role in carbon cycling

Mangrove zonation: « le cœur de Voh »

A zoned ecosystem

Eleva

tion

(MgTOC.ha-1) (Jaootot et al., in prep)

Avicennia marina Rhizophora sp

Total Stock (MgCOT.ha-1)

~ 23 ± 3 ~ 57 ± 3 ~ 143 ± 7 ~ 251 ± 22

Variability of carbon stock along the intertidal gradient

Role in carbon cycling

Salt-flat Avicennia Rhizophora

Net Ecosystem Productivity depends on climate

Barr et al., 2010; Chen et al., 2014; Leopold et al., submitted

NEP (gCO2 m-2 yr-1)

Role in carbon cycling

Atmospheric CO2 concentration

Mean surface temperature

Global sea level

Data: IPCC 2013

Climate change

(i) expand latitudinal distribution of mangroves (ii) change the zonation of mangrove species, (iii) increase the productivity of mangroves.

Increase the ability of mangrove to fix and store CO2?

-To establish long-term ecosystem research sites, where a set of ecological parameters

will be collected over many years: carbon exchange using the eddy covariance method,

leaf gas exchange (photosynthesis, stomatal conductance), growth (using low- and high-

resolution dendrometers), litter fall and decomposition, above and below-ground biomass.

-To determine how mangrove ability to fix CO2, and store carbon will evolve with climate

change (pCO2, sea level and temperature increases), studying different mangrove stands,

at different latitudes, and doing experiments in atmosphere controlled greenhouses.

Mangrove Observatory

-To help local communities to valorize this ability in carbon mitigation programs. -To help local communities to maintain their activity within the mangrove avoiding no-return disturbances.

-To integrate the monitoring and assessment of ecological indicators of the mangrove biodiversity with management practices.

-To train young researchers from developing countries in the area of mangrove ecosystems. - To disseminate knowledge to a wide audience (e.g., policy makers, environmental organizations, students, public at large).

Mangrove Observatory

Vietnam

NC

NZ

? ?

Latitudinal gradient of climate and biodiversity: - New Zealand, temperate, 1 mangrove specie - New Caledonia, semi-arid, 25 mangrove species - Vietnam, tropical, 60 mangrove species

Mangrove Observatory

In situ Instrumentation Eddy-covariance tower

The present

Mangrove Observatory

• Night : + = CO2 emission (respiration, photosynthesis = 0) = Source

• Day : - = CO2 sequestration (photosynthesis>respiration) = Sink

CO

2 flux

0

2

-4

Photosynthetic active radiation (PAR)

4 Days

Eddy-covariance

Mangrove Observatory

Eddy-covariance

Seasonal Influence on NEE (temperature / precipitation / VPD)

Mangrove Observatory

Lenght of immersion: -Transceiver - Ultrasound / laser - Video - Temperature probes - Salinity probes

9

1

2

7

8

4

5

6

shoreline

saltflat

Avicennia

Rhizophora

3

Tidal influence

Eddy-covariance

Mangrove Observatory

Mangrove growth under elevated CO2 concentrations Greenhouses experiments

- 3 atmosphere controlled greenhouses

- 800 ppm CO2 - Temperature / humidity - Lenght of tidal immersion

The Future of mangroves

Mangrove Observatory

…measurments of

- Biomass increase - Photosynthetic activity - Gaz exchange (CO2, O2, H2O) - Physico-chemical properties of soil - Evolution of carbon stock in soils - Decomposition experiments

Mangrove zonation: « le cœur de Voh »

Eleva

tion

Sea level Rise?

Mangrove Observatory

Remote sensing

- Some mangroves are keeping pace with sea-level (McKee et al., 2007) - Some are not depending on a number of global, regional, and local factors. - Some are moving landward…

Mangrove Observatory

Bluecham.net

Sea level rise Progradation of Avicennia on 2 years ?

- Currently, 3.4 billions of people leave less than 60 km from the coastline,

66% of the world population

- Hypothesis in 2030 : 75% of the world population

Need to have multi-stressors approach

Demographic pressure

- Population living at a height lower than 10 m (in millions of people) /

Surface covered by mangrove swamps (in ha, FAO) :

- China : 144 / 36 880

- India : 63 / 487 600

- Bangladesh : 62 / 622 000

- Vietnam : 43 / 252 500

- Indonesia : 42 / 3 493 110

- Thaïlande : 16 / 244 000

- Philippines : 13 / 127 610

Mangrove Observatory

Thank you

Mangrove Observatory