Destruction or persistence of coral atoll islands in the face of 20th and 21st century sea‐level rise?

Abstract

The future of low-lying reef islands has been the subject of international concern, scientific debate, and media interest in the last decade. As a result of sea-level rise, atoll islands are expected to become increasingly unstable and to be susceptible to potential depopulation by the end of the 21st century. Some have suggested that sea-level rise has already resulted in widespread erosion and inundation of atoll islands. Here, we analyze the physical changes in over 200 islands on 12 atolls in the central and western Pacific in the past few decades when sea level in the region increased at rates three to four times the global average. Results show little evidence of heightened erosion or reduction in island size. Instead island shores have adjusted their position and morphology in response to human impacts such as seawall construction and to variations in climate-ocean processes. These changes are reviewed and the role of sea-level rise is evaluated. The implications of this analysis are addressed in two parts. First, we consider the proposition that future sea-level rise will destabilize atoll islands to such an extent that their inhabitants will be forced to migrate offshore. And second, we identify a series of new challenges relating to risk reduction and adaptation policy for atoll island governments, international agencies, and island communities. These require a substantial shift away from the present adaptation paradigm of external migration and focus on the persistence of atoll islands and in-country solutions.

Reef Island Evolution and Dynamics: Insights from the Indian and Pacific Oceans and Perspectives for the Spermonde Archipelago

“…However, a primary conclusion from Webb and Kench (2010) was that sea-level rise had not caused widespread erosion of reef islands. With the exception of one study (Albert et al, 2016), similar conclusions have been drawn by subsequent studies that evaluated decadal-scale shoreline changes on reef islands based on the interpretation of remote sensing data (Ford, 2011(Ford, , 2013Rankey, 2011;Yates et al, 2013;Kench, 2014, 2016;Mann andWestphal, 2014, 2016;Mann, 2015;McLean and Kench, 2015;Mann et al, 2016b;Testut et al, 2016;Duvat and Pillet, 2017). Notably, Kench et al (2015) examined changes in islands of Funafuti atoll over more than a century, and also found a lack of consistency in island response, with the majority increasing in land area.…”

“…In contrast to narratives of island sinking, recent studies have emerged, which present evidence that reef islands are robust landforms that react dynamically to changes in oceanic and climatic boundary conditions across seasonal to millennial timescales (e.g., Kench and Brander, 2006b;Webb and Kench, 2010;McLean and Kench, 2015). Collectively, these studies show that physical island change is an ongoing process on reef islands with differential island erosion and accretion resulting in island migration on reef platforms and with many islands increasing in area.…”

Perspectives of artist–practitioners on the communication of climate change in the Pacific

“…Some evidence suggests that climate change impacts are already leading directly to migration within and beyond the region (Locke, 2009) although, for many people, it is not yet seen as a principal concern (Mortreux and Barnett, 2009). A range of other problems are faced across the Pacific in connection with climate change, including inundation of low-lying islands by the sea and beach erosion, flooding and saltwater intrusion to drinking supplies, and impacts on infrastructure (McLean and Kench, 2015;Mimura, 1999;Ellison and Fiu, 2010). Because of the particular vulnerability of islands in the Pacific to the consequences of climate change, regional bodies such as the Pacific Island Development Forum (PIDF), together with international groupings such as the Association of Small Island States (AOSIS), were along the most vocal advocates for the inclusion of an "aspiration" to keep global temperature rise to within 1.5°C at the 2015 Paris climate talks (Hoad, 2016; although this still fell short of a desire among many for 1.5°C to be set as a harder limit).…”

Classifying Pacific islands

“…With volcanic and composite islands, this may be because there are few opportunities for large islands to form here because of the few hotspots where point volcanism dominates; then, as such islands are moved away from the hotspot, they generally subside and are further reduced in size by denudation. The size of reef islands is ultimately limited by that of the reef foundations on which they are built but more commonly by the availability of island-building sediments (McLean and Kench 2015).…”