Bangladesh Sundarbans Research Articles

Ring width and vessel features of the mangrove Excoecaria agallocha L. depend on salinity in the Sundarbans, Bangladesh

The Bangladesh Sundarbans is the largest continuous mangrove in the world that providing crucial environmental services, particularly related to coastal protection and livelihoods of millions of people. However, anthropogenic disturbances, diseases infestation and environmental changes including sea level rise (SLR) and fresh-water flux into the delta are threatening the Sundarbans and other mangrove ecosystems worldwide. Protection of mangrove ecosystems requires knowledge on factors that mainly drive growth and vitality of tree species to evaluate which consequences can be expected from, mainly hydrology-related, environmental changes. In this study, we assessed the nature and periodicity of tree rings in Excoecaria agallocha, a wide spread mangrove species in the Bangladesh Sundarbans. We also analysed the influence of climatic factors, such as precipitation, temperature and vapor pressure deficit (VPD), and river discharge, as a proxy of salinity on ring width (RW) and vessel features, such as mean vessel area (MVA) and mean vessel density (MVD). E. agallocha forms distinct tree-ring boundary that characterized by a narrow (2–4 cells wide) band of radially flattened fibres. The RW as well as the MVA and MVD are crossdatable. The RW is mainly driven by salinity which is influenced by freshwater inputs through precipitation during monsoon along with river discharge January to April. The MVA and MVD responded to similar seasons and months as RW, but mostly with opposite signs in MVD. The results suggest that fresh water inputs through precipitation and river discharge positively influence the radial growth of E. agallocha in the Sundarbans. The RW and vessel features can be used as proxies to explore the growth dynamics of this species, especially in relation to global environmental changes.

Assessing Good Governance in Protected Areas (PA) Co-management: A Case Study of the Sundarbans Mangrove Forests of Bangladesh

ABSTRACT Co-management has been adopted in the Sundarbans of Bangladesh since 2008 toward biodiversity conservation and livelihood improvement of local communities. However, we have limited research on how good governance was maintained and practiced in co-managed mangrove protected areas (PA). Drawing on a case study, this research assessed stakeholders’ perception on good governance in PA co-management in the Sundarbans of Bangladesh. We adopted a ‘good governance framework’ consisting of six governance principles (stakeholders’ participation, transparency, responsiveness, legitimacy, fairness and organizational capacity) and deployed both qualitative (11 key-informants’ interviews and 4 focus group discussions) and quantitative methods (135 structured interviews) for data collection. Median, frequencies (percent), contingency table chi-square tests were performed for quantitative data. About 30–35% of the respondents perceived neutral in their responses to good governance principles (stakeholders’ participation, transparency, responsiveness, legitimacy, fairness and organizational capacity) indicating moderate level of governance in PA co-management in the Sundarbans. This study has demonstrated a wider implementation gap between the ambitious intent enshrined in the new policy framework and actual rollout of PA governance on the ground. These results would be useful to policy-makers, development agencies and PA managers in formulating and implementing effective policies for PA co-management in Bangladesh and elsewhere.

Parental influences on salt adaptive divergence of Sonneratia apetala (Buch.-Ham.) seedlings along the salinity gradient in the Sundarbans of Bangladesh

Salt adaptive variability facilitates mangroves to cope with salinity increase due to climate change. Sonneratia apetala is a pioneer mangrove species growing in the less-saline, moderate-saline and high-saline zones of the Sundarbans. A growth study with S. apetala seedlings of the three saline zones was conducted at different salinities in randomized block design to examine the parental effects on the variability in salt adaptability of this species along the salinity gradient in the Sundarbans. The highest survival (100%) from 0 to 10% salinities indicates the facultative nature of S. apetala. The survival, chlorophyll, diameter, height and biomass increment, proline, nutrients (N, P and K) and Na accumulation in different parts of the seedlings collected from the less-saline, moderate-saline and high-saline zones didn't vary significantly (p > 0.05) up to 20% salinity. However, at higher salinities, all the growth traits of the seedlings of the moderate-saline and high-saline zones were significantly (p<0.05) higher than those of the less-saline zone. These results demonstrated that the seedlings of S. apetala of the moderate-saline and high-saline zones are more salt adaptive than those of less-saline zone and clearly reflect the parental effects of S. apetala on its seedlings growth under different salinities. This divergence in salt adaptability among different saline zones due to parental effects makes S. apetala survive and grow in a wider salinity range in the Sundarbans and coastal plantations in Bangladesh.

Why some trees are more vulnerable during catastrophic cyclone events in the Sundarbans mangrove forest of Bangladesh?

Mangroves are recognised for their diverse set of ecosystem services, including protection from tropical cyclones and tidal surges. Mangroves are also adapted to withstand disturbances across a range of climatic conditions, and the frequency and severity of disturbances are projected to increase in the coming years due to climate change and sea-level rise. The Sundarbans of Bangladesh and India is one of the most frequently affected mangrove forests in South Asia. We investigated the effect of cyclone disturbance and stand characteristics on the survival of two dominant mangrove tree species – Heritiera fomes and Excoecaria agallocha. Data was collected through field surveys after cyclone Sidr, a category 5 cyclone that struck in the area in 2007, creating substantial forest damage. We used a Generalized Additive Mixed Model to analyse the effect of tree species, stem diameter at breast height (dbh), and tree spatial position in the forest stand on the degree of cyclonic damage. We find that cyclonic damage in the Sundarbans forest is sensitive to species and dbh. At similar tree size, Heritiera fomes was more vulnerable to cyclonic damage than Excoecaria agallocha. In Heritiera fomes the intensity of wind damage during cyclone increase with increasing dbh. In Sundarbans, cyclonic damage also depended on stand factors such as proximity to the riverbank or forest edges. We suggest silvicultural treatments, such as increasing the tapering of crown or decreasing height/dbh ratios of valuable species, could minimise future cyclonic damage in the area. Further investigations are necessary to improve the management of mangroves in the Sundarbans in the face of climate change, sea-level rise, and novel anthropogenic pressures.

Livelihood status of local communities around Sundarbans mangrove ecosystem in Shymnagar Upazila, Satkhira, Bangladesh

Abstract. Azad AK, Pitol MNS, Rakkibu MG. 2020. Livelihood status of local communities around Sundarbans mangrove ecosystem in Shymnagar Upazila, Satkhira, Bangladesh. Asian J For 5: 28-35. Sundarbans of Bangladesh is the largest single mangrove complex in the world which plays essential roles in delivering economic, ecological, and social functions, including providing livelihoods for local communities. The study aims to know the livelihood status and dependency of local people on Sundarbans in Shymnagar Upazila, Satkhira District, Bangladesh. A questionnaire survey was carried out in the studied area, involving 130 respondents in three unions. Most of the respondents (65%) were middle-aged (30-50 years old) and 22% of them were female and 78% were male. Among them about 51% were illiterate, 24% had primary education, while 25% had secondary education. About 72% of the respondents were fully dependent and 21% were partially dependent on Sundarbans for their livelihoods. Only 37% of people in these areas had their shrimp farm (gher). The respondents collected fuelwood (92%), aquatic resources (80%), small timber (54%), honey (27%), goran (Ceriops decandra) (8%), and golpata (Nypa fruticans) (6%) from Sundarbans. Only 63% of the respondents had their livestock like cows (2%), poultry (68%), and goats (30%), whereas 84% of respondents were involved with different NGOs. Among the respondents, 70% had the access to disaster warnings, whereas only 24% had shelter facilities. Only 28% of respondents had access to drinking water from deep tube-well and 33% from ponds. About 50% of the respondents did not get better medical treatment and were dependent on village doctors and only 8% of respondents received treatment from Government hospitals. It was alarming to know that about 91% of respondents did not know co-management in Sundarbans. Most of the people living here were not satisfied with their present occupations and about 98% of them were eager to start a new occupation. Only 11% of respondents got benefitted from government Vulnerable Group Feeding / Vulnerable Group Development support. The results of this study suggest that the government and different NGOs might provide necessary supports for local people so that they can start alternative occupations and their dependencies on the Sundarbans may be reduced significantly.

Is soil organic carbon underestimated in the largest mangrove forest ecosystems? Evidence from the Bangladesh Sundarbans

Globally, mangroves sequester a large amount of carbon into the sediments, although spatial heterogeneity exists owing to a wide variety of local, regional, and global controls. Rapid environmental and climate change, including increasing sea-level rise, global warming, reduced upstream discharge and anthropogenic activities, are predicted to increase salinity in the mangroves, especially in the Bangladesh Sundarbans, thereby disrupting this blue carbon reservoir. Nevertheless, it remains unclear how salinity affects the belowground soil carbon despite the recognised effect on above ground productivity. To address this gap, research was undertaken in the Bangladesh Sundarbans to compare total soil organic carbon (SOC) across three salinity zones and to explore any potential predictive relationships with other physical, chemical properties and vegetation characteristics. Total SOC was significantly higher in the oligohaline zone (74.8 ± 14.9 Mg ha−1), followed by the mesohaline (59.3 ± 15.8 Mg ha−1), and polyhaline zone (48.3 ± 10.3 Mg ha−1) (ANOVA, F2, 500 = 118.9, p < 0.001). At all sites, the topmost 10 cm of soil contained higher SOC density than the bottom depths (ANOVA, F3, 500 = 30.1, p < 0.001). On average, Bruguiera sp. stand holds the maximum SOC measured, followed by two pioneer species Sonneratia apetala and Avicennia sp. Multiple regression results indicated that soil salinity, organic C:N and tree diameter were the best predictor for the variability of the SOC in the Sundarbans (R2 = 0.62). Despite lower carbon in the soil, the study highlights that the conservation priorities and low deforestation rate have led to less CO2 emissions than most sediment carbon-rich mangroves in the world. The study also emphasised the importance of spatial conservation planning to safeguard the soil carbon-rich zones in the Bangladesh Sundarbans from anthropogenic tourism and development activities to support climate change adaptation and mitigation strategies.

Consumers' Perceptions of Organic Foods in Bangladesh: Challenges and Opportunities

This study aims at exploring the consumers' perceptions of organic foods. Additionally, this paper attempts to explore the existing problems to promote organic production. The significant issues include lack of awareness about organic technology and consumers’ trust in products and marketing systems. It is revealed that multi-factors influenced the choices of purchasing organic food. Educational qualification had a positive relationship with health and environmental awareness. However, there is a great potential to produce organic foods, particularly in a hilly region, and collect wild honey as organic foods from Sundarbans in Bangladesh. The cheaper wage is an opportunity for Bangladesh to intensify organic food production, generating decent jobs concomitantly. Lack of awareness, ecological consciousness, consumers' trust, certification, quality control mechanism, modern technologies, information literacy, storage capacity, and crop insurance were identified as the hindrances of flourishing the organic markets. In addition, the agricultural market chain is fragile, which is full of several intermediary groups. Furthermore, the availability of cheaper labor forces is a significant advantage of producing organic products that need intensive care.

Leaf anatomical adaptation of eighteen mangrove plant species from the Sundarbans in Bangladesh

Investigation on leaf anatomical adaptation of 18 mangrove plant species was carried out. Among the 18 species 13 were dorsiventral and five were isobilateral type. All the species had special stomatal structure and variable cuticle layer to minimize transpiration. Most of the species had succulent leaves with leaf thickness ranging from around 232 to 1363 μm. As an indication of salt secretion, both glandular and non-glandular trichomes were observed in several species. Although presence of single to multilayered hypodermis might effectively function as water storage tissue, several studied mangrove plant species e.g. Cynometra ramiflora L., Phoenix paludosa Roxb., Pongamea pinnata (L.) Pierre, Sonneratia apetala Buch. - Ham., S. caseolaris (L.) Engl. and Xylocarpus moluccensis (Lamk.) M. Roem. showed complete absence of hypodermis. This might be due to moderate saline condition. In addition, marked terminal tracheids in mesophyll tissue of a number of species might help with capillary water storage within the leaf. To enhance mechanical support several species were found to develop considerable amount of diverse sclereids within the mesophyll tissue and surrounding vascular bundle. Although maximum anatomical adaptations are common for plants growing in saline habitat it may be suggested that these features were differentially developed in plants specifically grown in mesohaline zone.

Molecular characterization of cellulolytic (endo- and exoglucanase) bacteria from the largest mangrove forest (Sundarbans), Bangladesh

PurposeCellulase, due to its massive applicability, has been used in various industrial processes such as biofuels (bioethanol, triphasic biomethanation), agricultural and plant waste management, chiral separation, and ligand binding studies. The finding of a novel cellulase-producing bacterium will benefit the industries, which rely on yeast to produce cellulase in fermentation technology, because bacteria can easily be manipulated and fermented cost-effectively.MethodsCellulase enzyme-secreting bacteria were isolated from different regions of the world’s largest mangrove forests, Sundarbans in Bangladesh. Biochemical, morphological, and 16S rRNA identification protocol was followed to precisely characterize the bacterial strains.ResultWe have determined that the strain T2-D2 (Bacillus sp.), E1-PT (Pseudomonas sp.), and D1-PT (Pseudomonas sp.) showed maximum endoglycolytic and strain C1-BT (Bacillus sp.), E1-BT (Bacillus sp.), and T-4 (E) showed relatively higher exoglycolytic activity during the test. So, it can be easily cultured at a normal temperature (97.7–99.5 °F). On the one hand, T2-D2 (Bacillus sp.) and E1-PT (Pseudomonas sp.) have shown the highest growth rate at pH 7 as it was neither acidic nor basic.ConclusionIt was concluded that the strain T2-D2 (Bacillus sp.) and E1-PT (Pseudomonas sp.) would be our target cellulolytic strains wherein the experimental isolates belonged to the Enterobacteriaceae, Psuedomonacea, Bacillacea, and Morganellacea family.

Valuing ecosystem services of Sundarbans mangrove forest for improved conservation: approach of randomized conjoint experiment

PurposeThis study provides empirical evidence of the economic valuation of ecosystem services. It examines the willingness-to-pay (WTP) and compensating surplus (CS) in response to policy change based on focus group discussion (FGD) and survey.Design/methodology/approachA randomized conjoint analysis based experiment was conducted in seven villages of Sundarbans in Bangladesh to elicit stated preference data and measure WTP and CS. Each respondent faced three options in every choice card-two hypothetical alternatives and one status quo scheme. Four alternatives – payment for ecosystem services, storm protection, erosion control and habitat for fish breeding – are randomly and simultaneously assigned to the two alternatives.FindingsThe findings suggest that age, income, education, family size and occupational status are the influential factor to choice the relevant attributes of ecosystem services and their levels. Villagers would like to pay annually Tk. 703, Tk. 281, and Tk. 59 for lower, moderate, and higher ecosystem services. With these WTP, they get surplus Tk. 760, Tk. 138, and Tk. 346 respectively.Research limitations/implicationsThe lower WTP does not necessarily imply low demand for ecosystem service, as the findings from WTP illustrate potential demand for ecosystem services of Sundarbans.Practical implicationsThe study provides an important insight into the ecosystem services and values of Sundarbans mangrove forests for welfare and can inform policy for sustainable use of resources of this forest.Originality/valueThere is a crucial gap in understanding what could villagers be ready for WTP for better ecosystem services of Sundarbans mangrove forest, how do payment based ecosystem services, as a proxy for the conservation of Sundarbans mangrove, and to what extent the policy can be strengthened.

Dictyota adnata Zanardini (Phaeophyceae) - A new record from the Sundarbans mangrove forests, Bangladesh

Samples were collected from Arpangasia and Kholpetua rivers within the Sundarbans in Bangladesh during February to March and December 2018. Among several forms was found a tightly prostrate brown alga occurring on moist parts of mangrove plants and clayey soil. Flattened brownish thalli tightly attached to pneumatophores and lower parts of mangrove trunks, spreading and branching dichotomously, sometimes overlapping and attached by means of unbranched marginal and sub-marginal rhizoids were collected. Distinct marginal sori are well developed in fertile specimens. On the basis of these characters, the sample has been identified as Dictyota adnata Zanardini which is herein reported as a new record for Bangladesh.

Valuing ecosystem services of Sundarbans Mangrove forest: Approach of choice experiment

This study examines the marginal willingness-to-pay (MWTP) and compensating surplus (CS) in response to the policy change of ecosystem services of Sundarbans based on focus group discussion (FGD) and survey. The choice experiment approach (CE) was conducted in seven villages of Sundarbans of Bangladesh to elicit stated preference data and measure MWTP and CS. Each respondent faced three options in every choice card-two hypothetical alternatives and one status quo scheme. Four ecosystem services-payment for ecosystem services, fish, shrimp larvae, and crab capture from canals and creeks, leaves, grasses and twigs collection, and fruits and honey collection are used to design choice cards. The findings suggest that age, income, education, family composition, and occupational status are the influential factors to choice the relevant attributes of ecosystem services. Respondents would like to pay more Tk. 0.015 in option 1, Tk. 0.086 in option 2 and Tk. 0.329 in option 3 for ecosystem services. With these MWTP, they get more surplus-Tk. 0.551 in option 3. The subsequent surplus will be estimated Tk. 0.105 in option 2 and Tk. 0.078 in option 1. The lower MWTP does not necessarily imply low demand for ecosystem services, as the findings from MWTP illustrate potential demand for ecosystem services of Sundarbans.

Deciphering the genetic diversity of Avicennia officinalis L. across the salinity gradient in the Sundarbans mangrove forest of Bangladesh

Mangroves adaptive plasticity in the changing environmental conditions is of vital importance for conservation management. Genetic diversity of mangrove brings about adaptive plasticity, enabling a species to cope with different habitat conditions. The Sundarbans of Bangladesh is the largest coastal wetland and mangrove forest with diversified habitat conditions that support a wide diversity of flora and fauna. Avicennia officinalis L. is the pioneer species in mangrove succession in the low-salinity, medium-salinity and high-salinity zones of the Sundarbans. Adopting RAPD-PCR analysis, the genetic diversity of A. officinalis was studied to explore the ecotypes of this species in the Sundarbans. The genetic distances of A. officinalis between the low-salinity and medium-salinity zones (0.50) and between the low-salinity and high-salinity zones (0.52) are significantly (p < 0.05) higher than that between the medium-salinity and high-salinity zones (0.09). The expected heterozygosity of A. officinalis of medium-salinity (0.54 ± 0.14) and high-salinity zones (0.55 ± 0.10) are higher than that of low-salinity zone (0.37 ± 0.12). The genetic diversity of A. officinalis of medium-salinity (0.5417 ± 0.3167) and high-salinity (0.5458 ± 0.3189) zones is significantly (p < 0.05) higher than that of low-salinity zone (0.3750 ± 0.2313). This genetic diversity of A. officinalis bears significant ecological consequences. A. officinalis growing in the low-salinity zone is the low salt-adapted ecotype while that growing in the medium-salinity and high-salinity zones is the high salt-adapted ecotype in the Sundarbans. These two ecotypes of A. officinalis are of both in-situ and ex-situ conservation importance for the Sundarbans and coastal plantations of Bangladesh to face the climate change induced salinity regime changes in the future.

Salinity drives growth dynamics of the mangrove tree Sonneratia apetala Buch. -Ham. in the Sundarbans, Bangladesh

Mangroves throughout the world are threatened by environmental changes apart from anthropogenic disturbances. Many of these changes may inhibit the growth and survival of mangrove species. To understand and predict the effects of global change on mangrove forests, it is necessary to obtain insights on the growth dynamics of mangroves in relation to environmental factors. This study was conducted on Sonneratia apetala, a mangrove species which grows under a range of salinity conditions across the Sundarbans in Bangladesh. We studied trees growing under respectively high, medium, and low salinity conditions based on the influence of freshwater discharge. First, the periodicity of radial growth across the year was detected by applying cambial analyses. Based on tree-ring analyses, we calculated the growth response of S. apetala to monthly variation in precipitation and temperature as well as river discharge, as a proxy for salinity. We found the cambium of S. apetala being active during the monsoon and post-monsoon period whereas it was dormant in the pre-monsoon. This periodicity in radial growth leads to the formation of distinct annual rings with ring boundaries being marked by radially flattened fibres. S. apetala trees growing under low salinity conditions generally show higher growth rates indicating the positive impact of river discharge, i.e. freshwater input on mangrove growth. Wet and warm conditions during the monsoon period positively affected S. apetala growth, especially in the low salinity zone. Our results show that salinity is the primary driver of growth dynamics of S. apetala in the Sundarbans. A gradual or seasonal increase in salinity, e.g. as a consequence of sea-level rise may therefore importantly alter the growth of this species, possibly leading to changes in mangrove forest dynamics and zonation.

Mangrove forest policy and management: Prevailing policy issues, actors’ public claims and informal interests in the Sundarbans of Bangladesh

Mangrove forests have enormous ecological and socio-economic importance for a number of different stakeholders and policy actors. Hence, a wide range of often conflicting material interests can be expected surrounding mangrove forest policy and management. These conflicts result in different issues of mangrove policy and management, on which different actors articulate their positions through publicly stated claims. It is unclear, in how far these publicly stated positions and claims resemble the formal interest of the actors only, or if they also reveal parts of their informal interests. In the Sundarbans mangrove forests, a number of issues have arisen, which are of contemporary policy concern. The aim of this study is to identify the most recent issues relating to the Sundarbans in Bangladesh and analyse the actors' claims/arguments on the identified issues which were publicly stated as an expression of formal or informal interest. In order to analyse these public claims, content analysis of selected Bangladeshi national newspapers, experts' deliberations and national policy documents was undertaken as an empirical method to ascertain relevant issues and actors' claims. A theory-based actor typology was applied to distinguish the relevant actors, and the concept of formal and informal interests was employed. The results indicate that the most salient policy issues around mangrove forest policy and management are: establishing Rampal power plant; protection of the Sundarbans forest area; environmental pollution; biodiversity conservation; reputation as a World Natural Heritage Site; relevance for climate change adaptation and mitigation; and local people's livelihoods. Government and Administration are found to be the most active actor in all the observed issues. Surprisingly, only very few administrations partake in public deliberations and the Prime Minister seems to dominate the public debate. This might be explained by the fact that the Rampal power plant project is perceived as the most contentious issue among all actors, with strong discursive support from the Prime Minister. In light of this issue structure, non-governmental actors as well as most bureaucracies are rarely found to actively engage in public debate on mangrove issues while informal interests were being displayed by Prime Minister and non-ruling political parties to a limited extent. Future empirical study to be conducted on the historical trajectory of Rampal power plant addressing the Prime Minister's arguments and environmental concerns of civil society actors. Also it would be worth to map the high degree of bureaucratic rivalry which can be assumed form the conflicting interest in mangrove forests between the responsible ministry—the Ministry of Environment, Forests and Climate Change (MoEFCC) and other ministries in their struggle for power.

Spatial differences in prey preference by tigers across the Bangladesh Sundarbans reveal a need for customised strategies to protect prey populations

The Sundarbans is the only mangrove habitat in the world to support tigers Panthera tigris, whose persistence there is believed to be dependent on a very limited number of prey species. Conservation managers therefore need to understand how tigers utilise available prey species on a spatial scale in order to formulate a prey-based protection strategy for this global-priority tiger landscape. A total of 512 scat samples were collected during a survey of 1984 km2 of forest across 4 sample blocks in the 6017 km2 of the Bangladesh Sundarbans. Analysis of scat composition and prey remains reliably identified 5 major prey species, of which spotted deer Axis axis and wild pig Sus scrofa contributed a cumulative biomass of 89% to tiger diet. Tiger preference for prey species was highly skewed towards spotted deer and wild pig, but the relative contribution of these 2 species differed significantly across the 4 study areas, which spanned the Sundarbans, demonstrating important spatial patterns of tiger prey preference across the Sundarbans landscape. Given the comparatively limited number of prey species available to support the dwindling tiger population, different strategies are needed in different parts of the Sundarbans to support tiger populations and to protect spotted deer and wild pig populations from unabated poaching.

Environmental change of coastal Sundarbans: Impact on livelihood and standard of living status of indigenous people

AbstractThere is overwhelming scientific consensus that environmental change is currently having ecological and socioeconomical impacts at the micro and macrolevel. Over the coming decades, the impact of development, climate change, and urbanization on the ecosystem is likely to become even more ruthless in the Sundarbans. Like many other ecologically sensitive areas, the Sundarbans of the Indian state of West Bengal and of Bangladesh are being stressed climatically to the extreme due to their geographical location. This study explores both the ways in which residents of communities in the West Bengal and Bangladesh Sundarbans perceive changes in the environment, as well as intergenerational changes in livelihoods to be driven in a large part by environmental changes. Persons from a total of 368 households were interviewed using a structured interview tool. As an example of differences in perception between residents of the two areas, survey respondents from communities of the Sundarbans of Bangladesh were more likely to perceive that rainfall amounts are changing than did the residents interviewed from the Sundarbans of West Bengal. From the sample data, it is shown that in the Sundarbans of Bangladesh, 59% of the respondents, as compared to 63% of the respondents in West Bengal, reported that they had chosen to enter their parents’ occupations. From the multivariate logistic regression analysis, it was observed that, especially in Bangladesh when compared to West Bengal, the state of the environment plays a vital role in whether respondents adopt occupations other than those of their parents.

Comparison of calorific values and ash content for different woody biomass components of six mangrove species of Bangladesh Sundarbans

The study of calorific values of mangrove plants is valuable indices for reflecting the energy conversion and material flow of the forest ecosystem. In this study, the calorific value and ash content of different biomass components, i.e. leaf, bark, sapwood and heartwood of six important mangrove species, namely goran (Ceriops decandra Griff. W. Theob.), keora (Sonneratia apetala Buch.-Ham.), passur (Xylocarpus mekongensis Pierre), sundri (Heritiera fomes Buch.-Ham.), gewa (Excoecaria agallocha L.) and jhana garjan (Rhizophora mucronata Lam.) of Bangladesh were evaluated. The gross calorific values (GCVs) and ash-free calorific values (AFCVs) of different biomass components of six species were in the range of 14.15–19.18 MJ/kg and 14.90–19.37 MJ/kg, respectively. Heartwood of H. fomes showed the highest GCV and AFCV among all of the mangrove species. The highest ash content (AC) was found for the bark of X. mekongensis (6.7%), while S. apetala sapwood and H. fomes bark showed the lowest AC (0.5%). The GCVs, AFCVs and ACs of different woody biomass components of six mangrove species were significantly different. The fuel value index (FVI) of heartwood and sapwood of six mangrove species was ranged between 1.34 for E. agallocha heartwood and 7.15 for H. fomes heartwood. The findings of this study are important for selecting the suitable fuelwood species for higher fuel value from and around the biggest single tract mangrove forest, the Sundarbans.

The hornless rhinoceros (Rhinoceros sondaicus inermis Lesson, 1836) discovered by Lamare-Picquot in the Sundarbans of Bangladesh in 1828, with notes on the history of his Asian collections

Abstract The French pharmacist and explorer Christoph-Augustin Lamare-Picquot (1785–1873) was in South Asia during 1826–1829 to collect ethnographical, anthropological, zoological and botanical specimens. He made an excursion to the Sundarbans (the Ganges-Brahmaputra delta) of Bangladesh, where on 17 November 1828 his team shot a female rhinoceros and caught her young one the next day, just south of Khulna. Both animals were completely hornless. He returned to France in the spring of 1830, where his zoological specimens were assessed by Georges Cuvier, and his other collections relating to ethnography by other scholars. All recommended purchase by the French Government, but circumstances did not allow this. A few animals were described by scientists connected with the Natural History Museum in Paris. After Lamare-Picquot published an account of the hunting expedition in 1835, the rhinoceros was described as a new species Rhinoceros inermis, by René-Primivère Lesson, first in a supplement to Buffon dated 1836, and not, as accepted until now, in restatements dating from 1838 or later. The main part of the zoological collection was bought by the Prussian King Friedrich Wilhelm III in 1836 and integrated in museums in Berlin. Other collections were exhibited as a “Panthéon Indien” in Vienna and Bratislava from 1838, until they were purchased by the Bavarian King Ludwig in 1841, and added to a museum in Munich. The type specimens of R. inermis are still preserved in the Museum für Naturkunde in Berlin. The adult female (ZMB_Mam_1957) was selected as the lectotype.

Adaptive responses to salinity: nutrient resorption efficiency of Sonneratia apetala (Buch.-Ham.) along the salinity gradient in the Sundarbans of Bangladesh

Sonneratia apetala (Buch.-Ham.) is a major pioneer tree species of the Sundarbans and is found to grow in the less saline zone (LSZ), moderate saline zone (MSZ) and high saline zone (HSZ) of this mangrove forest. This experiment examined the adaptive behaviour of S. apetala grown in different saline zones of the Sundarbans in terms of nutrient resorption/re-translocation efficiency (NRE). Samples of topsoil and green and senescent sun leaves were collected from S. apetala-dominated stands located in the three saline zones during the pre-monsoon, monsoon and post-monsoon seasons. Soil available nutrients (N, P and K), sodium (Na) concentrations, and NRE of S. apetala leaves from the three saline zones during the different seasons were measured in the laboratory. The average available nutrients (N, P and K); Na concentrations in the soil; and NRE of N, P and K showed significant (p < 0.05) differences among the saline zones and seasons. The lowest concentrations of N (25.44 µg/g), P (5.44 µg/g) and K (0.036 mg/g) and the highest concentrations of Na (0.50 mg/g) were observed in the HSZ during the pre-monsoon season. The highest NREs of N (63.58%), P (45.86%) and K (61.30%) were found in the HSZ during the pre-monsoon season, while the lowest NREs of N (39%), P (26%) and K (35%) were found in the LSZ during the post-monsoon season. The NRE was positively correlated with the available concentration of Na in the soil. Nutrient resorption is an important nutrient-conserving mechanism for mangroves growing under salt stress. This may be the reason that the NRE was comparatively higher in the HSZ than in the LSZ and MSZ. The findings of this study support the conclusion that S. apetala has shown adaptive responses among the populations in the LSZ, MSZ and HSZ of the Sundarbans. This adaptive variation enabled S. apetala to survive and grow satisfactorily in a wider range in the Sundarbans.