June 2020
Vol 6, Issue 24

About The Cover

Cover image expansion

ONLINE COVER Reef islands—which form on top of coral reef platforms from coral waste and other organic material—are one of the coastal environments most vulnerable to sea level rise. It is widely expected that these islands will drown in coming decades, with much of the discussion on the future of their inhabitants framed around either structural defenses or the exodus of island communities. However, Pacific Island nations themselves, such as Tuvalu and Kiribati, tend to focus on strategies that involve persistence and adaptation. In contrast to projections that assume reef islands are inert landforms that do not adjust over time, Masselink et al. used numerical modeling (validated with laboratory experiments) to simulate how these islands will evolve as a result of sea level rise. Their approach applies, for the first time, a wave-resolving morphodynamic model that accounts for sediment transport and morphodynamic feedback in addition to hydrodynamics. The researchers identified a spectrum of expected island responses ranging from islands that may remain and even grow as sea level rise to those that will inevitably drown. These findings suggest that natural adaptation of reef islands to changing conditions could potentially allow some of them to remain habitable, at least in the short term. [CREDIT: GREG LECOEUR/NATIONAL GEOGRAPHIC]