孟加拉国红树林海岸恢复力：潜在地点的识别、三重红利的评估和成本估算

Mangroves for Coastal Resiliencein Bangladesh Identification of Potential Locations, Assessmentof Triple Dividends, and Cost Estimation Alejandra Gijón MancheñoLuke BranderBramka Arga JafinoIgnacio UrrutiaSwarna Kazi Urban, Disaster Risk Management, Resilience and Land Global DepartmentJuly 2025 Policy Research Working Paper11175 Abstract Bangladesh is highly vulnerable to extreme weather eventsdue to its frequent exposure to floods and extensive low-ly-ing areas. Coastal flood risks are expected to increase dueclimate change. Therefore, Bangladesh has been upgradingits coastal embankment system to enhance flood safety. Thisinitiative includes not only hard flood defense infrastructure,but also nature-based solutions through planting mangroveson the seaside of embankments. Mangroves, serving as nat-ural flood barriers, have been utilized in Bangladesh forcoastal protection since the 1960s. However, their integra-tion with embankment designs and their benefits in carbonsequestration remain underexplored. This paper consoli-dates current knowledge on the role of mangroves in coastalresilience in Bangladesh, incorporating recent studies andnew analyses on their benefits on (i) flood risk reduction, (ii)livelihood enhancement, and (iii) carbon sequestration. The estimated benefits are mapped along the country’s coastalsystem. The study identifies some of the most beneficialmangrove sites to be combined with embankment designs,such as a belt south of polder 45 (Amtali) with an averagewidth of 1.77 kilometers, and a belt around the Kukri-Mukri polder with an average width of 1.82 kilometers.These mangrove forests can reduce the required thickness forslope protection by up to 80 percent, offer carbon servicebenefits of US$13,120 per hectare (over 2022–50, at a 6percent discount rate), and provide livelihood benefits ofmore than US$22,000 per hectare. Other wide mangrovebelts are found in Sandwip and Mirersarai. The findingsaim to guide future investments in integrating mangrovesinto coastal protection systems, highlighting their tripledividends for building resilience. The Policy Research Working Paper Series disseminates the findings of work in progress to encourage the exchange of ideas about developmentissues. An objective of the series is to get the findings out quickly, even if the presentations are less than fully polished. The papers carry thenames of the authors and should be cited accordingly. The findings, interpretations, and conclusions expressed in this paper are entirely thoseof the authors. They do not necessarily represent the views of the International Bank for Reconstruction and Development/World Bank andits affiliated organizations, or those of the Executive Directors of the World Bank or the governments they represent. Mangroves for Coastal Resilience in Bangladesh: Identification ofPotential Locations, Assessment of Triple Dividends, and CostEstimation AlejandraGijón Mancheño1,2,3,Luke Brander4,5,2,Bramka Arga Jafino2,Ignacio Urrutia2,Swarna Kazi2 1Delft University of Technology, Delft, The Netherlands2The World Bank3Invest International, The Netherlands4Vrije Universiteit Amsterdam, Amsterdam, The Netherlands5Leibniz University Hannover, Hannover, Germany JEL Codes:Q54, Q56, Q57Keywords: mangroves, resilience, benefits, assessment Acknowledgments: We would like to thank Thomas Dunlop (University of New South Wales), SuKalloe (Delft University of Technology), and Boris Ton Van Zanten (The World Bank) for their valuableinputs, comments, and feedbacks during the research and peer-review process of this paper. Thework is supported by the Global Facility for Disaster Reduction and Recovery (GFDRR). The workreceived technical support from the Global Program on Nature-Based Solutions of GFDRR. 1. Introduction Bangladesh is highly vulnerable to extreme weather events, since it is frequently exposed tofloodhazards and hostsa large population in low-lying areas. Inpreparation forrisingflood risks due toclimate change, the Government of Bangladesh upgraded the country’s coastalembankmentsystemto a higherfloodsafety standard, for instance through theCoastal Embankment RehabilitationProject and theCoastal Embankment Improvement Project. As part of the improvement works,mangroves—a group of salt-tolerant trees and shrubs—are being implemented on the seaside ofembankmentsto reduce coastal flooding. In Bangladesh, natural mangroves can be found in thesouthwest and southeast, while plantations are mostly located in the Meghna estuary(Figure 1),and, to a lesser extent, just to theeast from the Sundarbans and in the Chittagong division. Although mangrove trees have been planted in Bangladesh for coastal protection purposes since the1960s, existing mangrove fringes, natural or planted, are not currently considered in embankmentdesigns. This implies that in some instances, embankments could be lower or have a lighter wave-protection revetment due to the protective effect of existing vegetation. Mo