Decadal-scale Dynamics and Morphological Evolution of Mangroves and Beaches in a Reef-lagoon Complex, Mayotte Island

Jeanson, Matthieu; Dolique, Franck; Anthony, Edward J.; Aubry, Aline

doi:10.2112/si88-015.1

Cited by 14 publications

(18 citation statements)

References 34 publications

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“…Dispatched over 28 main areas, the surface of individual units varies from less than 1 ha to 183 ha (average ± standard deviation of 24 ± 38 ha). Mayotte has eight true mangrove tree species [40] in agreement with the ones found in Madagascar and in the eastern coast of Africa: Sonneratia alba Sm., Rhizophora mucronata Lam., Ceriops tagal (Perr.) C.B.Rob., Bruguiera gymnorhiza (L.) Savigny, Avicennia marina (Forssk.)…”

Section: Study Areasupporting

confidence: 76%

“…This study focused on the mangroves of Dembéni and Bandrélé located on the eastern coast of Mayotte 10 km apart (Figures 1 and 2). These fringing mangroves cover 44 ha and 36 ha, respectively [40]. They have regressed moderately since 1950, by −3.6% for Dembéni, and −5.6% for Bandrélé.…”

Section: Study Areamentioning

confidence: 98%

“…The coast is indented by numerous headlands enclosing sandy coves and sandy-muddy bays where mangroves have settled [39]. In 2016, mangroves occupied a surface of 694 ha [40] and 29% of the coastline. Dispatched over 28 main areas, the surface of individual units varies from less than 1 ha to 183 ha (average ± standard deviation of 24 ± 38 ha).…”

Section: Study Areamentioning

confidence: 99%

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Local Ecological Knowledge on Mangroves in Mayotte Island (Indian Ocean) and Influencing Factors

Longépée

Abdallah

Jeanson

et al. 2021

Forests

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The majority of studies on local ecological knowledge (LEK) relate to communities or groups relying on ecosystem(s) for their livelihood. In our case study, Mayotte Island, a French overseas department, very few people rely on mangrove ecosystem for natural resources but most of them are attached to it because of leisure activities and beliefs. The questions on mangrove LEK generally deal with a single aspect of ecological knowledge of surveyed people and is mixed with other information such as harvesting practices, anthropogenic impacts, and management issues. The aim of our study is to better understand the level of ecological knowledge of surveyed inhabitants of Mayotte and to assess whether factors linked to the profile of respondents have an influence on it. For this purpose, we carried out two main survey campaigns in three villages fringing two stable mangroves of Mayotte: the first one consisted of qualitative interviews and the second one, questionnaires lending quantitative results. Cross tabulations and Chi square tests of independence were carried out to determine the link between LEK and influencing factors. Results show that some LEK implying localized observation, such as the identification of mangrove trees and the knowledge of the coastal protection role of the mangrove, are well shared by surveyed people whereas others, such as the number and the name of mangrove tree species, are poorly known. The results also highlight the difficulty of questions implying observation at the landscape level and interpretation of observation. All the influencing factors selected have a significant influence on, at least, one LEK variable. The results highlight differences in LEK of villages bordering two nearby mangroves calling for a local management of these systems.

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Section: Study Areasupporting

confidence: 76%

Section: Study Areamentioning

confidence: 98%

Section: Study Areamentioning

confidence: 99%

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Local Ecological Knowledge on Mangroves in Mayotte Island (Indian Ocean) and Influencing Factors

Longépée

Abdallah

Jeanson

et al. 2021

Forests

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“…This basement topography can be represented by offshore reefs like in Mayotte where their characteristics are found to affect stability and erosion of mangrove along the coast. This results in large regional variability with mangrove system subject to advance or stability in the north and east of Mayotte but exhibiting a clearly regressive pattern along the southern and western shores (Jeansson et al, 2019). Finally, the basement topography also controls the presence or absence and the dynamic of tidal inlets, themselves controlling the evolutions of adjacent shorelines.…”

Section: Summary Of Contributionsmentioning

confidence: 99%

“…It is important to note that, in a number of contributions of this Special Issue, anthropogenic factors clearly emerge as an important driver of coastal change (Costa et al, 2019;Jeansson et al, 2019;Tessier et al, 2019). Unforeseen side effects of human activities, for example the implementation of dams, sand mining, irrigation systems are other anthropogenic factors that were not addressed.…”

Section: Summary Of Contributionsmentioning

confidence: 99%

Coastal Change in Tropical Overseas and Temperate Metropolitan France Inferred from a National Monitoring Network: A Summary from the Current Special Issue

Castelle

Chaumillon

2019

Journal of Coastal Research

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This paper provides an overview of the papers published in this Special Issue « Coastal Evolution under Climate Change along the Tropical Overseas and Temperate Metropolitan France » of Journal of Coastal Research. This special issue reflects the large diversity of mainland and tropical French coast and highlights the complex, siteand timescale-specific, combination of factors driving coastal evolution. Many contributions reveal a strong climate control on storm wave activity and, in turn, coastal response. In some contributions, the inherited geology and anthropogenic factors clearly appear affect coastal change. This special issue emphasises the need to monitor the coast combining different means to improve our understanding and predicting capacities of the natural variability of coastal response in a changing climate.

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Detecting the effects of rapid tectonically induced subsidence on Mayotte Island since 2018 on beach and reef morphology, and implications for coastal vulnerability to marine flooding

Jeanson¹,

Anthony

Charroux³

et al. 2021

Geo-Mar Lett

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Subsidence is a widespread phenomenon on the world's coasts. Mayotte, a coral reef-fringed archipelago in the SW Indian Ocean, experienced, in 2018 and 2019, 32 earthquakes with a recorded magnitude > 5 sourced by magmatic extraction from a deep reservoir 40-60 km east of the archipelago. This crisis resulted in island subsidence of up to 0.2 m. Profile measurements of three beaches in 2019-2021, referenced to benchmarks adjusted for subsidence, did not show any notable morphological change when compared to earlier profiles obtained in 2006/2008. This suggests that the rapid but limited subsidence has not significantly affected these systems, excluding eventual ecological repercussions that are not investigated here. Profile changes reflect seasonal variations in monsoon and trade-wind wave energy, and additionally the effect of local mild terrigenous sediment inputs. The sea-level rise caused by subsidence is, however, leading to more frequent spring high-tide flooding of some low back-beach areas and roads on the densely populated northeastern shores of the archipelago, the zone most affected by this tectonic movement. The case of Mayotte is interesting inasmuch as the subsidence caused by a distant submarine volcanic event has not been abrupt as in tectonically active areas nor continuous as in subsidence related, for instance, to glacio-isostatic readjustment, to continuous natural sediment compaction, or to anthropogenic loading. The crisis has been relatively quiescent since July 2021. Continuous monitoring will be needed to see how subsidence will eventually further affect the beach-reef flat systems of Mayotte.

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Decadal-scale Dynamics and Morphological Evolution of Mangroves and Beaches in a Reef-lagoon Complex, Mayotte Island

Cited by 14 publications

References 34 publications

Local Ecological Knowledge on Mangroves in Mayotte Island (Indian Ocean) and Influencing Factors

Local Ecological Knowledge on Mangroves in Mayotte Island (Indian Ocean) and Influencing Factors

Coastal Change in Tropical Overseas and Temperate Metropolitan France Inferred from a National Monitoring Network: A Summary from the Current Special Issue

Detecting the effects of rapid tectonically induced subsidence on Mayotte Island since 2018 on beach and reef morphology, and implications for coastal vulnerability to marine flooding

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