Applied sedimentology in the 21st century: addressing the challenges of sustainability of Pacific atoll islands

Many developing nations of the Indo–Pacific region are atoll island states. Due to their low elevations, they are especially susceptible to the impacts of climate change. This narrative is articulated in news items that report ongoing or imminent widespread erosion or drowning of islands as sea-level rises.

The purpose of this presentation is to describe how and why island shorelines are changing in Kiribati (and by analogy, other atoll nations), and the role of sedimentology in these dynamics. Results derived from field, remote-sensing, and modeling studies reveal that: 1) Sediment which makes up the islands is supplied from reef and transported generally lagoonward. Offshore sediment sources facilitate shoreline stability and growth, even with sea-level rise; nonetheless, 2) these systems also show considerable evidence for transport parallel to the margin; 3) transport is controlled by tide and wave energy, which can change seasonally, with ENSO shifts and longer-term climate changes, and as shaped by local factors; 4) Human modifications—seawalls, groins, or other obstacles to sediment supply by transport—can negatively impact island stability.

Collectively, these results emphasize the importance of understanding sedimentology, not in isolation, but along with traditional knowledge, to inform decision-making as atoll nations seek to construct more expansive and more resilient infrastructure. Yet, actionable sedimentologic insights remain challenging in many nations like Kiribati that do not have access to adequate data or the expertise to analyze the data. Similarly, public narratives ignorant of scientific understanding may result in development or aid programs which ‘miss the mark,’ or misrepresent the real needs on the ground.