Vegetation dynamics in the Bangladesh Sundarbans mangroves: a review of forest inventories
TL;DR: In this article, the results of four forest inventories have been analyzed to understand observed vegetation dynamics of the Sundarbans from 1926 to 1997, and the dominance of E. agallocha and C. decandra is shown to be decreasing at a much greater rate than H. fomes.
Abstract: The Sundarbans, the largest contiguous mangrove forest in the world, covers 6,017 km2 of the coastal zone of Bangladesh. Heritiera fomes Buch.-Ham., Excoecaria agallocha L. and Ceriops decandra (Griff.) Ding Hou jointly cover 95% of the forest area. In this study, the results of four forest inventories have been analyzed to understand observed vegetation dynamics of the Sundarbans from 1926 to 1997. The diversity of forest types has been gradually reduced over time, but H. fomes and E. agallocha have maintained their dominance over large portions of the forest. H. fomes is spread over 67% of the vegetated area of the forest, concentrated mostly in the northeastern area, and constitutes 75% of the density of trees with >15 cm dbh. The distribution and stem density of H. fomes show negative relationships with that of E. agallocha and C. decandra. In terms of coverage, E. agallocha is the most common species, spread over 74% of the vegetated area of the forest, and constitutes 39% of the density of trees with >2.5 cm dbh. On a longer timeframe (1926–1997), the dominance (coverage and density of larger diameter trees) of H. fomes as well as that of E. agallocha is declining. Even on parameters such as density of trees with >15 cm dbh, the dominance of E. agallocha is declining at a much greater rate than H. fomes. This observation contradicts the successional schemes proposed by different authors. This might indicate that theorizing successional schemes based on short-term observations on vegetation dynamics is not sufficient. The effect of human interference, changes in hydroedaphic condition and species interaction should be taken into consideration during explaining observed vegetation dynamics. Moreover, the need to understand vegetation trajectories at the micro-scale should be emphasized.
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University of Cambridge1, United States Department of State2, Florida Atlantic University3, Agricultural Research Service4, Florida Fish and Wildlife Conservation Commission5, Northeastern University6, University of New Hampshire7, Virginia Institute of Marine Science8, Silver Spring Networks9, Texas Parks and Wildlife Department10, University of Washington11, University of South Alabama12, The Nature Conservancy13
TL;DR: The first ever large-scale quantitative assessment of the extent and biomass of marine habitat-forming species over a 100-year time frame is presented, finding evidence for a 64 per cent decline in the spatial extent of oyster habitat and an 88% decline in oyster biomass over time.
Abstract: Historic baselines are important in developing our understanding of ecosystems in the face of rapid global change. While a number of studies have sought to determine changes in extent of exploited habitats over historic timescales, few have quantified such changes prior to late twentieth century baselines. Here, we present, to our knowledge, the first ever large-scale quantitative assessment of the extent and biomass of marine habitat-forming species over a 100-year time frame. We examined records of wild native oyster abundance in the United States from a historic, yet already exploited, baseline between 1878 and 1935 (predominantly 1885–1915), and a current baseline between 1968 and 2010 (predominantly 2000–2010). We quantified the extent of oyster grounds in 39 estuaries historically and 51 estuaries from recent times. Data from 24 estuaries allowed comparison of historic to present extent and biomass. We found evidence for a 64 per cent decline in the spatial extent of oyster habitat and an 88 per cent decline in oyster biomass over time. The difference between these two numbers illustrates that current areal extent measures may be masking significant loss of habitat through degradation.
245 citations
TL;DR: In this article, the authors reviewed the available scientific literature and found that socioeconomic impacts such as traditional livelihood displacement, social unrests and market fluctuations are hindering the sustainable development of shrimp farming in Bangladesh.
213 citations
Cites background from "Vegetation dynamics in the Banglade..."
...The remaining mangrove forests are under pressure by continuous cutting, encroachment, storms and climate change (Iftekhar and Saenger, 2008)....
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TL;DR: This work traces the areal change that the Indian Sundarbans have undergone over the last two-and-a-half centuries using a multi-temporal and multi-scale approach based on historical maps and remote sensing data to detect changes in mangrove cover.
Abstract: Covering approximately 10,000 km2 the Sundarbans in the Northern Bay of Bengal is the largest contiguous mangrove forest on earth. Mangroves forests are highly productive and diverse ecosystems, providing a wide range of direct ecosystem services for resident populations. In addition, mangroves function as a buffer against frequently occurring cyclones; helping to protect local settlements including the two most populous cities of the world, Kolkata and Dhaka, against their worst effects. While large tracts of the Indian Sundarbans were cleared, drained and reclaimed for cultivation during the British colonial era, the remaining parts have been under various protection regimes since the 1970s, primarily to protect the remaining population of Bengal tigers (Panthera tigris ssp. tigris). In view of the importance of such forests, now severely threatened worldwide, we trace the areal change that the Indian Sundarbans have undergone over the last two-and-a-half centuries. We apply a multi-temporal and multi-scale approach based on historical maps and remote sensing data to detect changes in mangrove cover. While the mangroves’ areal extent has not changed much in the recent past, forest health and structure have. These changes result from direct human interference, upstream development, extreme weather events and the slow onset of climate change effects. Moreover, we consider the role of different management strategies affecting mangrove conservation and their intersection with local livelihoods.
177 citations
Cites background from "Vegetation dynamics in the Banglade..."
...Change detection analysis (Figure 4) shows that the new sedimentary deposits along small tidal channels are colonized within a couple of years by light demanding pioneer plant communities which are later replaced by different successional communities due to land rise and modified inundation and salinity conditions [70]....
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TL;DR: In this article, the authors used Landsat images spanning from 1973 to 2010, and an algorithm that was developed, consistently estimate the spatiotemporal dynamics of erosion and accretion for four different time intervals and the whole study period.
142 citations
TL;DR: In this paper, the authors presented the estimation of ecosystem carbon stock in the Sundarbans using a large scale data set collected from systematic grid samples throughout the forest, and the results revealed that no matter whether the mangroves are tall or dwarf, a significant amount of carbon is stored into the sediment.
Abstract: The Sundarbans (21o30′–22o30′ N and 89o00′–89o55′ E) is the largest mangrove forest in the world. Forests are very important for sequestering atmospheric carbon and mangroves are amongst the most efficient in carbon sequestration. This study presents the estimation of ecosystem carbon (above- and belowground) stock in the Sundarbans using a large scale data sets collected from systematic grid samples throughout the forest. The variation of carbon stock in different vegetation types and in different salinity zones in Sundarbans was investigated. The relationships between carbon stock and different vegetation functional attributes (basal area, mean tree height, crown coverage etc.) were also investigated. The amount of carbon stored varied significantly among vegetation types, salinity zones and vegetation functional attributes (P < 0.05). Sundri (Heritiera fomes) dominated forest types store more ecosystem carbon (360.1 ± 22.71 Mg C ha−1) than other vegetation types. The fresh water zone shows the highest ecosystem carbon stock (336.09 ± 14.74 Mg C ha−1) followed by moderate and strong salinity zones. Salinity was found to enhance belowground carbon stock as revealed by the lowest proportion of belowground carbon stock (57.2 %) with respect to ecosystem carbon in fresh water zone and by the highest (71.9 %) in strong salinity zone. The results also reveal that no matter whether the mangroves are tall or dwarf, a significant amount of carbon is stored into the sediment. The vegetation attributes (basal area and mean tree height) of the dominant mangrove species in each vegetation type were identified as the key indicator of ecosystem carbon stock. We recommended some generalized regression equations to predict ecosystem carbon stock from basal area or mean tree height.
138 citations
Cites background from "Vegetation dynamics in the Banglade..."
...The forest is, nationally and internationally, of great conservation significance for its environmental services and biodiversity (Seidensticker and Hai 1983; Iftekhar and Saenger 2008)....
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...The forest is, nationally and internationally, of great conservation significance for its environmental services and biodiversity (Seidensticker and Hai 1983; Iftekhar and Saenger 2008)....
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...4 FR fresh water zone, MO moderate saline zone, and ST strong saline zone Source (Chaffey et al. 1985; Iftekhar and Saenger 2008) Wetlands Ecol Manage (2015) 23:269–283 271...
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...In Sundarbans there are ten prominent vegetation types (Table 2) (Chaffey et al. 1985; Iftekhar and Saenger 2008)....
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References
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Book•
01 Jan 1986TL;DR: The aim of this work is to contribute to the human awareness of the natural world and to contribute towards the humanizing of nature.
Abstract: Preface Acknowledgements Part I. General Account: 1. Ecology 2. Floristics 3. Biogeography 4. Shoot systems 5. Root systems 6. Water relations and salt balance 7. Flowering 8. Seedlings and seeds 9. Utilization and exploitation Part II. Detailed Descriptions by Family References Index.
2,014 citations
"Vegetation dynamics in the Banglade..." refers background in this paper
...In mangrove forest, zonation is often interpreted as the expression of succession (Tomlinson 1986)....
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01 Jan 1987
TL;DR: In this paper, a detailed description of mangroves and their environment is given, as well as a textbook on the ecology of MANGODA, with a detailed overview of the mangrove ecology.
Abstract: Textbook on the ecology of mangroves, detailed description of mangroves and their environment.
403 citations
TL;DR: In this paper, the authors have devised a sufficiently accurate coastal mapping methodology providing statistics on the actual areal extent of mangrove types and sub-types, both at local and continental scales.
Abstract: The mangroves located around the Bay of Bengal and along the coast ofSouth China Sea are of special interest for many reasons. This coastlinereceives three major tropical rivers (Ganges, Irrawaddy, Mekong) and it hasthe world's largest mangrove stands in a single block (the Sunderbans). Thecontrasted climatic conditions from sub-arid (southeastern India), to moist(coastal Cambodia), and the extreme diversity of human impacts in one ofthe world's highest population densities (West Bengal in India andBangladesh), have created a mosaic of mangrove types that are floristicallyrich and with different histories, different ecological frameworks and distinct evolutionary trends.For the first time, we draw together remote sensing data along withessential structural and physiognomic parameters of mangrove forest areas.We have devised a sufficiently accurate coastal mapping methodologyproviding statistics on the actual areal extent of mangrove types andsub-types, both at local and continental scales. Some results are entirelynew, and others provide comparison with existing data. The exact extentof mangroves in Myanmar was previously unknown. Using remote sensingwe also demonstrate the magnitude of the ongoing deforestation in thiscountry. The current location and status of mangrove forests in the affectedarea are described using the methodology which is also being applied inother sites around the world.
153 citations
"Vegetation dynamics in the Banglade..." refers background in this paper
...Thus, if the rate of decline continues, this species will become endangered as it presently is in India and Myanmar (Blasco et al. 2001)....
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...Thus, if the rate of decline continues, this species will become endangered as it presently is in India and Myanmar (Blasco et al. 2001)....
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...Heritiera fomes is distributed in Myanmar, India, and Bangladesh (Das and Siddiqi 1985)....
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