Rates of shoreline change along the coast of Bangladesh

Bangladesh, at the confluence of the sediment-laden Ganges and Brahmaputra Rivers, supports an enormous and rapidly growing population (>140 million in 2011), across low-lying alluvial and delta plains that have accumulated over the past few thousand years. It has been identified as one of the most vulnerable places in the world to the impacts of climate change and sea-level rise. Although abundant sediment supply has resulted in accretion on some parts of the coast of Bangladesh, others are experiencing rapid erosion. We report a systematic assessment of rates of shoreline change over a 20-year period from 1989 to 2009, using Landsat satellite images with pixel resolution of 30 m on the ground. A Band ratio approach, using Band-5 divided by Band-2, discriminated the water line on images that were largely cloud-free, adequately registered, and at comparable tidal stages. Rates of shoreline change were calculated for >16,000 transects generated at 50 m intervals along the entire mainland coastline (>1,100 km) and major islands, using the End Point Rate (EPR) method in the Digital Shoreline Analysis System (DSAS) extension in ArcGIS®. Erosion characterises most of the seaward margin of the Sundarbans in western Bangladesh. Retreat rates of up to 20 m/yr are typical, with little evidence that local devastation of the mangrove fringe by Cyclone Sidr in November 2007 had resulted in uncharacteristic long-term rates of retreat where it made landfall. Erosion exceeded accretion in the Barguna Patuakhali coastal zone, most of which eroded at up to 20 m/yr, but with truncation of the southern tip of the Patharghata Upazila at up to 100 m/yr. In Bhola, erosion at rates of up to 120 m/yr were observed along much of the coast, but in the Noakhali Feni coastal zone, similar rates of erosion were balanced by rapid accretion of the main promontory by more than 600 m/yr. Rates of change were more subdued in the Chittagong and Cox’s Bazar coastal zones of southeast Bangladesh. Islands in the Meghna estuary were especially dynamic; Hatiya Island accreted along some of its shoreline by 50 km² between 1989 and 2009, but lost 65 km² through erosion elsewhere, resulting in the island moving south. Similar trends were observed on adjacent islands. The overall area changed relatively little across the entire coastline over the 20-year period with accretion of up to 315 km², countered by erosion of about 307 km².     

Functional relationship between ammonia-oxidizing bacteria and ammonia-oxidizing archaea populations in the secondary treatment system of a full-scale municipal wastewater treatment plant

The abundance of ammonia-oxidizing bacteria and archaea and their amoA genes from the aerobic activated sludge tanks, recycled sludge and anaerobic digesters of a full-scale wastewater treatment plant (WWTP) was determined. Polymerase chain reaction and denaturing gradient gel electrophoresis were used to generate diversity profiles, which showed that each population had a consistent profile although the abundance of individual members varied. In the aerobic tanks, the ammonia-oxidizing bacterial (AOB) population was more than 350 times more abundant than the ammonia-oxidizing archaeal (AOA) population, however in the digesters, the AOA population was more than 10 times more abundant. Measuring the activity of the amoA gene expression of the two populations using RT-PCR also showed that the AOA amoA gene was more active in the digesters than in the activated sludge tanks. Using batch reactors and ddPCR, amoA activity could be measured and it was found that when the AOB amoA activity was inhibited in the anoxic reactors, the expression of the AOA amoA gene increased fourfold. This suggests that these two populations may have a cooperative relationship for the oxidation of ammonia.     

A STOCHASTIC MODEL TO EVALUATE RIPARIAN IRRIGATION EXPANSION IN THE EASTERN UNITED STATES1

ABSTRACT: Irrigation has expanded in parts of the eastern United States. In some areas, the adjoining surface (riparian) water is the most economical source of irrigation water. Expanded demand for riparian water may lead to conflict among irrigators and other streamflow users. Accurate information on the potential for and impacts of riparian irrigation expansion is needed to decide if control of such expansion is necessary. In this study, a stochastic economic model to evaluate the impacts of potential irrigation expansion is presented. The model considers the soil, location, and land use characteristics of individual sites, as well as weather and streamflow patterns. The application of the model to an eastern Virginia watershed indicates that, with maximum potential expansion, water availability becomes limited and yields will be reduced in some years. As a result, the expected net returns from irrigation and the probability of breaking even on the investment are reduced substantially. The results suggest the need to consider regulation of surface water allocation for irrigation development in riparian watersheds.     

The Impact of Policy and Institutional Environment on Costs and Benefits of Sustainable Agricultural Land Uses: The Case of the Chittagong Hill Tracts,Bangladesh

As in other mountain regions of Asia, agricultural lands in the Chittagong Hill Tracts (CHT) of Bangladesh are undergoing degradation due primarily to environmentally incompatible land-use systems such as shifting cultivation (jhum) and annual cash crops. The suitable land-use systems such as agroforestry and timber tree plantation provide benefit to the society at large, but they might not provide attractive economic benefits to farmers, eventually constraining a wide-scale adoption of such land-use systems. Therefore, it is essential to evaluate agricultural land-use systems from both societal and private perspectives in the pursuit of promoting particularly environmentally sustainable systems. This article evaluated five major land-use systems being practiced in CHT, namely jhum, annual cash crops, horticulture, agroforestry, and timber plantation. The results of the financial analysis revealed the annual cash crops as the most attractive land use and jhum as the least attractive of the five land-use systems considered under the study. Horticulture, timber plantation, and agroforestry, considered to be suitable land-use systems particularly for mountainous areas, held the middle ground between these two systems. Annual cash crops provided the highest financial return at the cost of a very high rate of soil erosion. When the societal cost of soil erosion is considered, annual cash crops appear to be the most costly land-use system, followed by jhum and horticulture. Although financially less attractive compared to annual cash crops and horticulture, agroforestry and timber plantation are the socially most beneficial land-use systems. Findings of the alternative policy analyses indicate that there is a good prospect for making environmentally sustainable land-use systems, such as agroforestry and timber plantation, attractive for the farmers by eliminating existing legal and institutional barriers, combined with the provision of necessary support services and facilities.

Assessment of heavy metal toxicants in the roadside soil along the N-5, National Highway, Pakistan

The assessment of the toxicants in roadside soil on regular basis has become extremely essential with the increase in awareness for the metal toxicity in the environment. The present study investigates the presence of toxic metals along National Highway (N-5), Pakistan. Averages of about 1.3 million per month of automobile vehicles ply on this route. Lead (Pb), zinc (Zn), copper (Cu), nickel (Ni), cadmium (Cd), cobalt (Co), manganese (Mn), mercury (Hg), and iron (Fe) were analyzed by atomic absorption spectrophotometry in roadside soil at the nine selected locations along the highway. Strong Pearson correlations (α = 0.05) were found between Pb and Zn (r(2)?= 0.887), Fe and Mn (r(2)?= 0.880), Hg and Cd (0.864), Cu and Zn (0.838), and Cu and Pb (0.814). The correlation between the elemental compositions of the main automobile components revealed vehicular traffic as the main non-point source of roadside soil pollution. Extremely high level of mercury, 144.05 mg kg(-1), was found at S5. It was revealed that the unregulated incineration and dumping sites of hazardous waste material along N-5 were also responsible for these contaminations. Multivariate analysis on the obtained data also disclosed the same interpretation. Cluster analysis of the data grouped Pb, Zn, and Cu at 85.23% similarity, whereas, Cd, Hg, and Ni were grouped at 78.75% similarity basis. The findings need swift action against the root cause of soil pollution.     

A research on conventional and modern algorithms for maximum power extraction from wind energy conversion system: a review

Environmental Science and Pollution Research - In the last few decades, wind energy has become a significant source of the renewable energy system, and it is essential to use wind energy for...     

Groundwater-dependent irrigation costs and benefits for adaptation to global change

The effects of a 1.5 °C global change on irrigation costs and carbon emissions in a groundwater-dependent irrigation system were assessed in the northwestern region of Bangladesh and examined at the global scale to determine possible global impacts and propose necessary adaptation measures. Downscaled climate projections were obtained from an ensemble of eight general circulation models (GCMs) for three representative concentration pathways (RCPs), RCP2.6, RCP4.5, and RCP8.5 and were used to generate the 1.5 °C warming scenarios. A water balance model was used to estimate irrigation demand, a support vector machine (SVM) model was used to simulate groundwater levels, an energy-use model was used to estimate carbon emissions from the irrigation pump, and a multiple linear regression (MLR) model was used to simulate the irrigation costs. The results showed that groundwater levels would likely drop by only 0.03 to 0.4 m under a 1.5 °C temperature increase, which would result in an increase in irrigation costs and carbon emissions ranging from 11.14 to 148.4 Bangladesh taka (BDT) and 0.3 to 4% CO₂ emissions/ha, respectively, in northwestern Bangladesh. The results indicate that the impacts of climate change on irrigation costs for groundwater-dependent irrigation would be negligible if warming is limited to 1.5 °C; however, increased emissions, up to 4%, from irrigation pumps can have a significant impact on the total emissions from agriculture. This study revealed that similar impacts from irrigation pumps worldwide would result in an increase in carbon emissions by 4.65 to 65.06 thousand tons, based only on emissions from groundwater-dependent rice fields. Restricting groundwater-based irrigation in regions where the groundwater is already vulnerable, improving irrigation efficiency by educating farmers and enhancing pump efficiency by following optimum pumping guidelines can mitigate the impacts of climate change on groundwater resources, increase farmers’ profits, and reduce carbon emissions in regions with groundwater-dependent irrigation.     

Identifying future research directions for biodiversity,ecosystem services and sustainability: perspectives from early-career researchers

We aimed to identify priority research questions in the field of biodiversity, ecosystem services and sustainability (BESS), based on a workshop held during the NRG BESS Conference for Early Career Researchers on BESS, and to compare these to existing horizon scanning exercises. This work highlights the need for improved data availability through collaboration and knowledge exchange, which, in turn, can support the integrated valuation and sustainable management of ecosystems in response to global change. In addition, clear connectivity among different research themes in this field further emphasizes the need to consider a wider range of topics simultaneously to ensure the sustainable management of ecosystems for human wellbeing. In contrast to other horizon scanning exercises, our focus was more interdisciplinary and more concerned with the limits of sustainability and dynamic relationships between social and ecological systems. The identified questions could provide a framework for researchers, policy makers, funding agencies and the private sector to advance knowledge in biodiversity and ES research and to develop and implement policies to enable sustainable future development.     

Soil salinity,household wealth and food insecurity in tropical deltas: evidence from south-west coast of Bangladesh

As a creeping process, salinisation represents a significant long-term environmental risk in coastal and deltaic environments. Excess soil salinity may exacerbate existing risks of food insecurity in densely populated tropical deltas, which is likely to have a negative effect on human and ecological sustainability of these regions and beyond. This study focuses on the coastal regions of the Ganges–Brahmaputra delta in Bangladesh, and uses data from the 2010 Household Income and Expenditure Survey and the Soil Resource Development Institute to investigate the effect of soil salinity and wealth on household food security. The outcome variables are two widely used measures of food security: calorie availability and household expenditure on food items. The main explanatory variables tested include indicators of soil salinity and household-level socio-economic characteristics. The results of logistic regression show that in unadjusted models, soil salinisation has a significant negative effect on household food security. However, this impact becomes statistically insignificant when households’ wealth is taken into account. The results further suggest that education and remittance flows, but not gender or working status of the household head, are significant predictors of food insecurity in the study area. The findings indicate the need to focus scholarly and policy attention on reducing wealth inequalities in tropical deltas in the context of the global sustainable deltas initiative and the proposed Sustainable Development Goals.