Shoreline changes in coral reef islands of the Federated States of Micronesia since the mid-20th century

Sengupta, Meghna; Ford, Murray R.; Kench, Paul S.

doi:10.1016/j.geomorph.2020.107584

Cited by 16 publications

(15 citation statements)

References 54 publications

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“…Furthermore, ongoing sea-level rise at a rate of 3.46 ± 0.25 mm.y −1 throughout the archipelago 47 may continue to drive mobility of the island at a pace similar to that of the past half-century. The migration of island shorelines away from exposed reef crests in response to increased sea level is consistent with a number of other studies of island change 12 , 16 , 17 .…”

Section: Discussionsupporting

confidence: 89%

Reef islands have continually adjusted to environmental change over the past two millennia

et al. 2023

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Global environmental change is identified as a driver of physical transformation of coral reef islands over the past half-century, and next 100 years, posing major adaptation challenges to island nations. Here we resolve whether these recent documented changes in islands are unprecedented compared with the pre-industrial era. We utilise radiometric dating, geological, and remote sensing techniques to document the dynamics of a Maldivian reef island at millennial to decadal timescales. Results show the magnitude of island change over the past half-century (±40 m movement) is not unprecedented compared with paleo-dynamic evidence that reveals large-scale changes in island dimension, shape, beach levels, as well as positional changes of ±200 m since island formation ~1,500 years ago. Results highlight the value of a multi-temporal methodological approach to gain a deeper understanding of the dynamic trajectories of reef islands, to support development of adaptation strategies at timeframes relevant to human security.

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Section: Discussionsupporting

confidence: 89%

Reef islands have continually adjusted to environmental change over the past two millennia

et al. 2023

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“…Many studies of atoll geomorphology use a combination of field and remote sensing technologies, including historic aerial photography and modern satellite imagery, ranging from a focus on one motu to a regional group of atolls. Frequently studies have relied on hand digitation of shorelines and atoll morphology (Duvat & Pillet, 2017;Paul Simon Kench, Chan, et al, 2014;Sengupta et al, 2021;Webb & Kench, 2010). Different features are used as a proxy for the shoreline location including edge of vegetation (Albert et al, 2016a;M.…”

Section: Previous Work Bymentioning

confidence: 99%

“…Motu form and evolve on a shorter time scale, decades to centuries (Paul Simon Perry et al, 2013;C D Woodroffe et al, 1999), than the atoll itself, millennia to hundreds of thousands of years (M. Toomey et al, 2013; M. R. Toomey et al, 2016). Motu initiation, formation, and evolution has occured under current (Paul Simon Kench, Chan, et al, 2014;Sengupta et al, 2021), rising (Paul S Kench et al, 2005;McLean & Kench, 2015a;Webb & Kench, 2010), and falling sea level conditions (Colin D. Woodroffe et al, 2007). Evolution of motu can be episodic, with island change tied to specific events such as a tropical cyclone that added sediment to the system (Duvat & Pillet, 2017) or land reclamation from human activities (Aslam & Kench, 2017a;Duvat & Magnan, 2019;Duvat & Pillet, 2017;M.…”

Section: Introductionmentioning

confidence: 99%

Development of a World-Wide Database of Atoll Morphometrics

Johnson

Ortiz

2022

Preprint

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Small Island Nations are at considerable risk of climate change impacts from sea-level rise to coral acidification to increasing cyclone intensity; understanding how they will change in the coming century is vital for climate mitigation and resiliency. Atoll morphometrics are calculated for 3,795 motu and 593 reef flats on 154 atolls. The total land (motu) area is 1,836.55 km 2 with a total reef flat area of 7,387.43 km 2 . A consistent methodology to classify, segment, and calculate morphometrics is used. Composites are created for 4 years (2015)(2016)(2017)(2018), and are classified into motu, reef flat, open water/lagoon via unsupervised classification. Morphometrics are computed for each motu and reef flat of the atoll in python, creating a database of atolls and their associated morphometrics. Consistency in processing removes spatial and user bias, enabling a better understanding of geographic patterns of atolls. We identify trends in atoll, motu, and reef flat formations. The average atoll reef flat width is 850 ± 817 m and the average motu width is 263 ± 210 m. Distinct differences in the distribution of motu can be seen on a regional scale in French Polynesia, while globally, wider reef flats with larger motu are found closest to the equator. Globally there is a consistent reef flat width in front of large motu (> 10 km length) of 188 ±156 m. Our atoll morphometric database creates a baseline of current atoll characteristics that can be expanded upon in the future and used for evaluating temporal changes to atoll islands.

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“…Over decadal timescales, research has assessed changes to reef island planform areas, and rates and magnitudes of shoreline movements using remote sensing techniques. In the Indian and Pacific Oceans, reef islands appear to be highly geomorphologically dynamic, and able to adjust their shoreline positions during periods of sea-level rise and coral reef degradation [11,[21][22][23][24][25][26][27]. Indeed, many of these islands have exhibited a range of accretionary behaviours, including expansion towards the ocean or lagoon side of the reef platform, and lateral (spit and extremity) accretion from the central island core [11,28,29].…”

Section: Introductionmentioning

confidence: 99%

Honduran Reef Island Shoreline Change and Planform Evolution over the Last 15 Years: Implications for Reef Island Monitoring and Futures

Husband,

East,

Hocking

et al. 2023

Remote Sensing

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Assessing the vulnerability of low-lying coral reef islands is a global concern due to predictions that climate and environmental change will increase reef island instability and cause reef island populations to be among the first environmental refugees. Reef islands in the Pacific and Indian Oceans are highly dynamic environments that morphologically adjust to changing environmental conditions over annual-decadal timescales. However, there is a paucity of reef island shoreline change data from the Caribbean where sea-level rise, ecological and environmental disturbance and hydrodynamic regimes are considerably different than in other oceans globally. Here we present shoreline change analysis of 16 reef islands in northern Honduras, at the southern end of the Mesoamerican Barrier Reef. Satellite imagery from a maximum period of 12.4 years from Utila (2006–2019), and 2.4 years from Cayos Cochinos (2018–2021) was analysed to quantify island shoreline change and planform morphological adjustments. We identified accretion as the dominant island behaviour in Utila, where 5 of 7 islands increased in area and 61.7% of shorelines accreted, contributing to an overall net area increase of 9.4%. Island behaviour was more variable in Cayos Cochinos, where 55.7% of shorelines eroded, 5 of 9 islands remained stable, and net island area change was insignificant (2%). Conversely, the 4 smallest Cayos Cochinos islands (all <1500 m2) experienced significant shoreline change, potentially highlighting a new size threshold for considering reef island evolution. Across both sites, reef islands demonstrated a range of modes of planform change, including lateral accretion and erosion, and migration. Consequently, we provide the first empirical evidence of the dynamic nature of Caribbean reef islands during a period coincident with sea-level rise and highlight the heterogeneous nature of reef island evolution between and within two neighbouring sites at timescales relevant for island adaptation efforts.

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Shoreline changes in coral reef islands of the Federated States of Micronesia since the mid-20th century

Cited by 16 publications

References 54 publications

Reef islands have continually adjusted to environmental change over the past two millennia

Reef islands have continually adjusted to environmental change over the past two millennia

Development of a World-Wide Database of Atoll Morphometrics

Honduran Reef Island Shoreline Change and Planform Evolution over the Last 15 Years: Implications for Reef Island Monitoring and Futures

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