Mangroves and shoreline erosion in the Mekong River delta, Viet Nam

Type Article
Date 2019-10
Language English
Author(s) Besset Manon1, 2, Gratiot Nicolas3, 4, Anthony Edward J.1, 5, Bouchette Frédéric1, Goichot Marc6, Marchesiello Patrick7
Affiliation(s) 1 : University of Montpellier, Geoscience Montpellier, Montpellier, France
2 : Aix Marseille University, CNRS, IRD, INRA, Coll France, CEREGE, Aix-en-Provence, France
3 : CARE, Ho Chi Minh City University of Technology, VNU-HCM, Viet Nam
4 : Université Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, F-38000, Grenoble, France
5 : USR LEEISA, CNRS, Cayenne, French Guiana
6 : Lead, Water, WWF Greater Mekong Programme, 14B Ky Dong Street, Ward 9, District 3, Ho Chi Minh, Viet Nam
7 : IRD, LEGOS, 14 Avenue Edouard Belin, 31400, Toulouse, France
Source Estuarine Coastal And Shelf Science (0272-7714) (Elsevier BV), 2019-10 , Vol. 226 , P. 106263 (9p.)
DOI 10.1016/j.ecss.2019.106263
WOS© Times Cited 46
Keyword(s) Mangroves, Mekong river delta, Shoreline erosion, Coastal squeeze, Sediment supply

The question of the rampant erosion of the shorelines rimming the Mekong River delta has assumed increasing importance over the last few years. Among issues pertinent to this question is how it is related to mangroves. Using high-resolution satellite images, we compared the width of the mangrove belt fringing the shoreline in 2012 to shoreline change (advance, retreat) between 2003 and 2012 for 3687 cross-shore transects, spaced 100 m apart, and thus covering nearly 370 km of delta shoreline bearing mangroves. The results show no significant relationships. We infer from this that, once erosion sets in following sustained deficient mud supply to the coast, the rate of shoreline change is independent of the width of the mangrove belt. Numerous studies have shown that: (1) mangroves promote coastal accretion where fine-grained sediment supply is adequate, (2) a large and healthy belt of fringing mangroves can efficiently protect a shoreline by inducing more efficient dissipation of wave energy than a narrower fringe, and (3) mangrove removal contributes to the aggravation of ongoing shoreline erosion. We fully concur, but draw attention to the fact that mangroves cannot accomplish their land-building and coastal protection roles under conditions of a failing sediment supply and prevailing erosion. Ignoring these overarching conditions implies that high expectations from mangroves in protecting and/or stabilizing the Mekong delta shoreline, and eroding shorelines elsewhere, will meet with disappointment. Among these false expectations are: (1) a large and healthy mangrove fringe is sufficient to stabilize the (eroding) shoreline, (2) a reduction in the width of a large mangrove fringe to the benefit of other activities, such as shrimp-farming, is not deleterious to the shoreline position, and (3) the effects of human-induced reductions in sediment supply to the coast can be offset by a large belt of fringing mangroves.

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