Responding to rising sea levels in the Mekong Delta

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Abstract

Vietnamese communities in the Mekong Delta are faced with the substantial impacts of rising sea levels and salinity intrusion. The construction of embankments and dykes has historically been the principal strategy of the Vietnamese government to mitigate the effects of salinity intrusion on agricultural production. A predicted sea-level rise of 30 cm by the year 2050 is expected to accelerate salinity intrusion. This study combines hydrologic, agronomic and behavioural assessments to identify effective adaptation strategies reliant on land-use change (soft options) and investments in water infrastructure (hard options). As these strategies are managed within different policy portfolios, the political discussion has polarized between choices of either soft or hard options. This paper argues that an ensemble of hard and soft policies is likely to provide the most effective results for people’s livelihoods in the Mekong Delta. The consequences of policy deliberations are likely to be felt beyond the Mekong Delta as levels of rice cultivation there also affect national and global food security.

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Figure 1: Relationship between soil salinity and yields of rice varieties of variable salinity tolerances based on multiple field trials in 2005–2010.
Figure 2: Salinity intrusion (indicated by an increasing red colouration) for the all-driver scenario, including 30 cm of sea-level rise, development of all planned upstream reservoirs and irrigation schemes, and an increase in dry years.
Figure 3: Recommended land-use change for the all-driver scenario, which includes 30 cm of sea-level rise, development of all proposed upstream reservoirs and irrigation streams, and an increasing number of dry years.
Figure 4: Recommended land-use change for the hard adaptation scenario, which includes the upgrade of existing sea-dykes and the construction of major estuary sluice gates in Cai Lon, Cai Be, Ham Luong and Co Chien.
Figure 5: Ability of households to replace income losses in Tra Vinh, Can Tho and An Giang based on an integrated simulation model.

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Acknowledgements

The author wish to thank M. Kirby and M. Mainuddin for their constructive comments. The authors are grateful for the funding received from the DFAT CSIRO Research for Development Alliance.

Author information

A.S. was lead author of this paper, designed the study and the simulation model, co-designed the survey instrument and the hydrologic scenarios, and analysed the results. J.W. contributed extensively to the writing of this manuscript, designed the study and the survey instrument, and analysed the survey results. T.Q.T. contributed to the writing, designed the hydrologic scenarios, and conducted their implementation and the hydrologic analysis. N.H.T. contributed to the writing, designed the hydrologic scenarios, conducted their implementation and the hydrologic analysis, analysed land-use suitability, and designed the overall study. D.K.N. contributed to the writing, designed the survey instrument, implemented the households survey, analysed land-use suitability, conducted the agronomic analysis, and designed the overall study. L.Q.T. contributed to the writing and to the assessment of land-use suitability. V.P.D.T. contributed to the writing and to the hydrologic simulations. P.T.V. contributed to the writing, to the assessment of land-use suitability, and developed the maps.

Correspondence to A. Smajgl.

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The authors declare no competing financial interests.

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Smajgl, A., Toan, T., Nhan, D. et al. Responding to rising sea levels in the Mekong Delta. Nature Clim Change 5, 167–174 (2015) doi:10.1038/nclimate2469

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