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Mangroves have been identified as blue carbon ecosystems that are natural carbon sinks. In Bangladesh, the establishment of mangrove plantations for coastal protection has occurred since the 1960s, but the plantations may also be a sustainable pathway to enhance carbon sequestration, which can help Bangladesh meet its greenhouse gas (GHG) emission reduction targets, contributing to climate change mitigation. As a part of its Nationally Determined Contribution (NDC) under the Paris Agreement 2016, Bangladesh is committed to limiting the GHG emissions through the expansion of mangrove plantations, but the level of carbon removal that could be achieved through the establishment of plantations has not yet been estimated. The mean ecosystem carbon stock of 5–42 years aged (average age: 25.5 years) mangrove plantations was 190.1 (±30.3) Mg C ha−1, with ecosystem carbon stocks varying regionally. The biomass carbon stock was 60.3 (±5.6) Mg C ha−1 and the soil carbon stock was 129.8 (±24.8) Mg C ha−1 in the top 1 m of which 43.9 Mg C ha−1 was added to the soil after plantation establishment. Plantations at age 5 to 42 years achieved 52% of the mean ecosystem carbon stock calculated for the reference site (Sundarbans natural mangroves). Since 1966, the 28,000 ha of established plantations to the east of the Sundarbans have accumulated approximately 76,607 Mg C year−1 sequestration in biomass and 37,542 Mg C year−1 sequestration in soils, totaling 114,149 Mg C year−1. Continuation of the current plantation success rate would sequester an additional 664,850 Mg C by 2030, which is 4.4% of Bangladesh's 2030 GHG reduction target from all sectors described in its NDC, however, plantations for climate change mitigation would be most effective 20 years after establishment. Higher levels of investment in mangrove plantations and higher plantation establishment success could contribute up to 2,098,093 Mg C to blue carbon sequestration and climate change mitigation in Bangladesh by 2030. [ABSTRACT FROM AUTHOR]

This article compares the politics of climate change in the Sundarbans region in Bangladesh and India based on ethnographic fieldwork in four villages and among migrants from these villages in Kolkata and Khulna city by focusing on the long aftermath of cyclone Aila. The comparison highlights different policy options and framings of extreme weather events. Ten years after the cyclone, the aftermath of Aila continues in both regions we studied in Bangladesh and India, but partly for different reasons. In our study areas in Bangladesh, the aftermath of Aila reinforced the neglect of coastal livelihoods, whereas, in the communities we studied in India, Aila spurred new investments in the affected areas. By comparing how the political is interwoven with the natural, we demonstrate how Aila's lingering impacts have emerged as part of local power relationships and diverse forms of agency. We highlight the multiplicity of policy responses and people's practices not only between communities and countries facing a similar predicament but also within the communities themselves. We argue that the politics of climate change is not only about climate change policy to mitigate the impact of ecological disasters but also about the reconstruction of political agents and practices. [ABSTRACT FROM AUTHOR]

• Afforested mangroves take decades to reach similar structure to natural mangroves. • Tree communities achieved equivalent biomass to natural mangroves within 20 years. • Structural complexity was higher in older plantations than younger plantations. • Equivalent species richness to natural mangroves was not reached within 42 years. • Planting a diverse mix of species could improve the diversity of plantations. Afforestation is a process used in recovering the global mangrove cover. Succession or development in mangrove communities during mangrove afforestation has rarely been described yet is important for understanding the potential of afforestation in creating diverse and functional mangroves. Since 1966, the Government of Bangladesh has created nearly 280 km2 of plantation mangroves (7.5% of the extent of the Sundarbans mangrove forest and 0.21% of the global mangroves extent) on the Delta of the Ganges, Brahmaputra and Meghna Rivers, located east of the Sundarbans mangroves. Here, we investigated the development of these plantation mangroves, assessing their community structure and species richness over a 40-year chronosequence in comparison to natural mangroves in the same region. Tree communities in the plantations reached a maximum mean aboveground biomass (AGB) of ∼157 ± 13 Mg dry weight ha−1, achieving equivalence in tree aboveground biomass and tree density (255 ± 2 individuals ha−1) to natural mangroves by 20 and 39 years respectively. Our dataset from plantations aged between 10 and 42 years indicated that structural complexity (I c) was higher in older plantations than in younger plantations. We found that the tree community structure of older mangrove plantations was more diverse in the eastern region of the delta compared to the central and western regions, and the landward plantations were more diverse than the plantations fringing the oceans. One of the originally planted mangrove species, Sonneratia apetala , was dominant in these plantations. However, we recorded 8 mangrove tree species from 5 genera in the plantations, despite only two species (S. apetala and Avicennia officinalis) being planted. Our data indicated that while the tree structure of the established mangrove plantations was similar to natural mangroves within 42 years, equivalent species richness may not be reached for more than 40 years. Therefore, adoption of management to enhance natural successional or development processes in afforestation programs, for example by planting a diverse mix of species, could improve the effectiveness of afforestation in conserving biodiversity. [ABSTRACT FROM AUTHOR]