Jan studied Geography and is using Geographical Information Systems (GIS) and the Dynamic Interactive Vulnerability Assessment-(DIVA)-Tool to analyze the present and the future exposure of population to coastal hazards on the global scale. As future population cannot be predicted, Jan is using the population projections of the Shared Socioeconomic Pathways (SSPs), which provide five scenarios on population development until 2100. The SSP population projections provide population totals on national levels but do not provide spatial explicit (gridded) population numbers. Studies show that population development in coastal and non-coastal areas as well as in urban and rural areas differs. Jan and his colleagues developed spatially explicit population projections, entitled coastal SSPs, which expand the global SSPs to the coastal zone and account for these differences in population development. Besides the quantitative component, the coastal SSPs consist of qualitative narratives describing future development in coastal. The population totals on national level are consistent with the projected population used in the SSP framework and do not differ. Further, Jan compared the exposure based on the coastal SSPs to the exposure based on other spatially explicit population projection and non-spatial population projections. He found that differences in the downscaling approaches can lead to considerable differences on exposure, which exceed the magnitude of differences in exposed population due to high and low sea-level rise projections. For improving the assessment of the present exposure, Jan tested different approaches to redistribute population within administrative units. Census data usually report population per administrative-unit and do not provide information on finer spatial detail. Thus, exposure analysis assumes homogeneous population distribution within administrative units, which can lead to considerable over- or underestimation of the actual exposure. Jan showed that these inaccuracies can be reduced if information on settlement patterns derived from satellite images are used to redistribute population.
In his future work, Jan is planning to account for the spatial distribution of different age groups. Studies show that the vulnerability of young children and elderly people is higher than the vulnerability of the average population. Not accounting for this can lead to an underestimation of vulnerability in aging societies and in societies with a high fertility.
MERKENS, J.-L., VAFEIDIS, A. (2018): Using Information on Settlement Patterns to Improve the Spatial Distribution of Population in Coastal Impact Assessments. Sustainability 10(9):3170. doi:10.3390/su10093170
NICHOLLS, R., BROWN, S., GOODWIN, P., WAHL, T., LOWE, J., SOLAN, M., GODBOLD, J., HAIGH, I., LINCKE, D., HINKEL, J., WOLFF, C. and J. MERKENS (2018): Stabilization of global temperature at 1.5°C and 2.0°C: implications for coastal areas. In: Philosophical Transactions of the Royal Society A 376. doi:10.1098/rsta.2016.0448.
REIMANN, L., MERKENS, J.L. and A.T. VAFEIDIS (2018): Regionalized Shared Socioeconomic Pathways: Narratives and spatial population projections for the Mediterranean coastal zone. In: Regional Environmental Change 18 (1), p. 235-245. doi: 10.1007/s10113-017-1189-2.
MERKENS, J.-L., REIMANN, L., HINKEL, J. and A. VAFEIDIS (2016): Gridded population projections for the coastal zone under the Shared Socioeconomic Pathways. In: Global and Planetary Change 175, p. 57-66.
Christian-Albrechts-Universität zu Kiel
+49 (0)431 880 1701