Global sea-level rise and coastal vulnerability

Global sea-level has fluctuated through geological time but the sea-level oscillations during the Quaternary and especially the last Ice Age were particularly important in shaping our modern coastline. At the last glacial maximum of 20,000 years ago, the sea level was around 120 m lower than today. It then rose rapidly to reach its current position around 6–7,000 years ago. During this period, there were times when the sea level was rising at rates in excess of 20 mm year, although the pattern, timing and rates of this major sea-level rise event vary around the world, as does the time when sea level stabilised near its present position (Harvey 2006). After a few millennia of relative stability, geological and tide-gauge data provide evidence of sea-level rise during the 19th and 20th centuries, reaching an average rate of 1.7 mm year during the 20th century (Church and White 2006). This modern sea-level rise raised concerns about the vulnerability of the significant population living near the coast, for which there are various global and sub-global estimates (Mimura 2001; Small and Nicholls 2003; Ericson et al. 2006; Woodroffe et al. 2006; McGranahan et al. 2007; Nicholls et al. 2007). Recent satellite data, combined with tide-gauge data, provide evidence of an increased sea-level rise of over 3 mm year (see Church et al.; this volume). The need to better understand the causes of sea-level rise, provide accurate predictions of the future rate of sealevel rise and to assess coastal vulnerability has been the subject of numerous scientific articles in the global change literature, which have recently been reviewed and synthesised in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (Parry et al. 2007; Solomon et al. 2007). The feature articles in this issue of Sustainability Science provide a useful contribution to this continuing debate. The idea for this issue arose from discussions following a special session on sea-level rise, held at the Open Science Conference of the ESSP (Earth Systems Science Partnership) in November 2006, Beijing, China. The ESSP comprises a partnership of the world’s four leading global change scientific research organisations: (1) DIVERSITAS (International Program for Biodiversity Science); (2) IGBP (International GeosphereBiosphere Programme); (3) IHDP (International Human Dimensions Project); and (4) WCRP (World Climate Research Program). The co-chairs of the special conference session on sealevel rise (Wilson and Harvey) brought scientists together from different global change research programs (largely the WCRP and IGBP) to present different perspectives on sea-level rise. This followed recent research efforts from the WCRP, which held a workshop in 2006 on sea-level rise and vulnerability (see Church et al.; this volume) and the IGBP and its coastal program LOICZ (Land–Ocean Interactions in the Coastal Zone), which recently published a 10-year research synthesis (Crossland et al. 2005). Four of the speakers from the ESSP conference (Church, Harvey, Nicholls and von Storch) have contributed articles to this issue of Sustainability Science with the additional help of a number of their fellow researchers. A further two papers (Syvitski and Torresan et al.) have been included to broaden the scope of the debate. The first three papers focus on physical aspects of sea-level rise, whereas the last N. Harvey (&) Geographical and Environmental Studies, University of Adelaide, Adelaide, SA 5400, Australia e-mail: nick.harvey@adelaide.edu.au