Impact of land subsidence on the population and land use in the Mekong delta Applying environmental feedback to the Shared Socio-economic Pathways to provide projections for delta regions

Abstract

The Shared Socio-economic Pathways (SSP) provide global projections of future land use and population. These are modelled in integrated assessment models such as the Integrated Model to Assess the Global Environment known as IMAGE (PBL, 2019). Because, global models do not take local environmental feedback into account, downscaling the SSP scenarios and translating these one to one upon a delta, such as the Mekong delta which is relatively large and important on a global scale, can cause the global models to project changes that will not occur in certain areas. This negatively affects the reliability of the projections, providing a challenge for large delta regions; especially with a high population density and intensive agriculture, as these are prone to local environmental feedback, e.g. land subsidence (Minderhoud, 2019). The SSP are used in planning for areas, therefore it is not only of scientific relevance to make the SSP scenarios as accurate as possible but also relevant for society.

The question this research tried to answer is: what is the impact of land subsidence on the projections of the SSP models for the Mekong delta region and its inhabitants? The impact was shown by firstly displaying the projection of the land use and population density of the Mekong delta for each SSP. Showing the overall amount of rice cultivation and number of inhabitants in the Mekong delta and how these are spatially distributed throughout the delta. Secondly, by displaying the projections of relative sea level rise (RSLR) for each SSP. Showing that for each SSP scenario a substantial part of the Mekong Delta will be under sea level in 2100, for the more extreme scenarios even earlier, and comparing this with the current situation. Thirdly, by showing how the expected RSLR alters the land use opportunities in the Mekong delta. Displaying how the projected land use opportunities are diminished by the RSLR, since large parts of the delta are likely to be located below sea level in the coming century. Fourthly, by explaining how the population and its resources are affected by the RSLR. Classification of the elevation for the projected rice and population shows the effect of RSLR on the population and it resources. Finally, by showing to what extent there is a mismatch between the SSP projections of land use and population and the feasible land use and population density, when taking the effects of RSLR into account.