A review of the drivers of 200 years of wetland degradation in the Mekong Delta of Vietnam

This paper examines the anthropogenic factors that have contributed to wetland loss and degradation in the Mekong Delta, Vietnam from 1816 AD to present. Our analysis is framed over five historical periods and highlights the role that seven drivers of wetland degradation have played in the Mekong Delta, including: resettlement and economic development policies; population growth and urbanization; demand for food and reclaiming wetland for agriculture; construction of canals construction of dykes flood protection systems; expansion of travel systems (waterway and roads); and exploitation of wetland natural resources. Of these, government policies for resettlement and economic development seem to have had the greatest impact on wetland loss and degradation in the Mekong Delta throughout the course of history. As a result of these factors, only 0.068 million hectares of the original 4.0 million hectares of the Mekong Delta currently remains as primary swamp forest ecosystem. History suggests that future management of the Mekong Delta should take a holistic approach that includes a better understanding of the implications of past decisions on wetland loss.     

Opportunities and challenges for mangrove carbon sequestration in the Mekong River Delta in Vietnam

Increasing value is attributed to mangroves due to their considerable capacity to sequester carbon, known as ‘blue carbon’. Assessments of opportunities and challenges associated with estimating the significance of carbon sequestered by mangroves need to consider a range of disciplinary perspectives, including the bio-physical science mangroves, social and economic issues of land use, local and international law, and the role of public and private finance. We undertook an interdisciplinary review based on available literature and fieldwork focused on parts of the Mekong River Delta (MRD). Preliminary estimates indicate mangrove biomass may be 70–150 t ha^?1, but considerably larger storage of carbon occurs in sediments beneath mangroves. These natural stores of carbon are compromised when mangroves are removed to accommodate anthropogenic activities. Mangroves are an important resource in the MRD that supplies multiple goods and services, and conservation or re-establishment of mangroves provides many benefits. International law and within-country environmental frameworks offer increasing scope to recognize the role that mangrove forests play through carbon sequestration, in order that these might lead to funding opportunities, both in public and private sectors. Such schemes need to have positive rather than negative impacts on the livelihoods of the many people living within and adjacent to these wetlands. Nevertheless, many challenges remain and it will require further targeted and coordinated scientific research, development of economic and social incentives to protect and restore mangroves, supportive law and policy mechanisms at global and national levels, and establishment of long-term financing for such endeavours.     

Dissolved phosphorus transport from soil to surface water in catchments with different land use

Diffuse phosphorus (P) export from agricultural land to surface waters is a significant environmental problem. It is critical to determine the natural background P losses from diffuse sources, but their identification and quantification is difficult. In this study, three headwater catchments with differing land use (arable, pasture and forest) were monitored for 3 years to quantify exports of dissolved (<0.45 µm) reactive P and total dissolved P. Mean total P exports from the arable catchment ranged between 0.08 and 0.28 kg ha^?1 year^?1. Compared with the reference condition (forest), arable land and pasture exported up to 11-fold more dissolved P. The contribution of dissolved (<0.45 µm) unreactive P was low to negligible in every catchment. Agricultural practices can exert large pressures on surface waters that are controlled by hydrological factors. Adapting policy to cope with these factors is needed for lowering these pressures in the future.     

Capacity assessment to secure COVID-19 waste treatment in Vietnam

Journal of Material Cycles and Waste Management - The accelerated generation of COVID-19 waste under the Delta-fuelled outbreak placed a sudden burden on waste disposal in Vietnam. To secure the...     

Using Relative Risk to Compare the Effects of Aquatic Stressors at a Regional Scale

The regional-scale importance of an aquatic stressor depends both on its regional extent (i.e., how widespread it is) and on the severity of its effects in ecosystems where it is found. Sample surveys, such as those developed by the U.S. Environmental Protection Agency’s Environmental Monitoring and Assessment Program (EMAP), are designed to estimate and compare the extents, throughout a large region, of elevated conditions for various aquatic stressors. In this article, we propose relative risk as a complementary measure of the severity of each stressor’s effect on a response variable that characterizes aquatic ecological condition. Specifically, relative risk measures the strength of association between stressor and response variables that can be classified as either “good” (i.e., reference) or “poor” (i.e., different from reference). We present formulae for estimating relative risk and its confidence interval, adapted for the unequal sample inclusion probabilities employed in EMAP surveys. For a recent EMAP survey of streams in five Mid-Atlantic states, we estimated the relative extents of eight stressors as well as their relative risks to aquatic macroinvertebrate assemblages, with assemblage condition measured by an index of biotic integrity (IBI). For example, a measure of excess sedimentation had a relative risk of 1.60 for macroinvertebrate IBI, with the meaning that poor IBI conditions were 1.6 times more likely to be found in streams having poor conditions of sedimentation than in streams having good sedimentation conditions. We show how stressor extent and relative risk estimates, viewed together, offer a compact and comprehensive assessment of the relative importances of multiple stressors.     

Forest resources and household welfare: Empirical evidence from North Central Vietnam

Using secondary data from a socio-economic quantitative household survey of the North Central region of Vietnam, the main aim of our study is to analyze the causal effect of forest resources on household income and poverty. Based on the observed characteristics of a forest-based livelihood and forest-related activities, we use a propensity score matching (PSM) method to control for potential bias arising from self-selection. The PSM results indicate that households with a forest-based livelihood had a higher level of income and lower poverty rates than did those without. Interestingly, our findings confirm that a forest-based livelihood offers much higher income than any other type of livelihood adopted by local households. Also, the poverty rate among households with a forest-based livelihood is lower than those earning non-labor income or engaged in wage/crop and crop livelihoods. Among households and provinces, we find varying opportunities deriving from forest resources, suggesting that there are potential barriers hindering local households from pursuing a forest livelihood or participating in some forest activities. Therefore, government policy and regulations on forest management should focus on improving the access of households to forest resources, while enhancing the sustainability of these resources.     

Changes in motorcycle-related injuries and deaths after mandatory motorcycle helmet law in a district of Vietnam

Objective: Our study measured the change in head injuries and deaths among motorcycle users in Cu Chi district, a suburban district of Ho Chi Minh City.

Methods: Hospital records for road traffic injuries (RTIs) were collected from the Cu Chi Trauma Centre and motorcycle-related death records were obtained from mortality registries in commune health offices. Head injury severity was categorized using the Abbreviated Injury Score (AIS). Rate ratios (RRs) were used to compare rates pre- and post-law (2005/2006–2009/2010). Cu Chi's population, stratified by year, age, and sex, was used as the denominator.

Results: Of records identifying the transportation mode at the time of injury, motorcyclists accounted for most injuries (3,035, 87%) and deaths (238, 90%). Head injuries accounted for 70% of motorcycle-related hospitalizations. Helmet use was not recorded in any death records and not in 97% of medical records. Males accounted for most injuries (73%) and deaths (88%). The median age was 28 years and 32 years for injuries and deaths, respectively. Compared to the pre-law period, rates of motorcycle injuries (RR = 0.53; 95% confidence interval [CI], 0.49–0.58), head injuries (RR = 0.35; 95% CI, 0.31–0.39), severe head injuries (RR = 0.47; 95% CI, 0.34–0.63), and deaths (RR = 0.69; 95% CI, 0.53–0.89) significantly decreased in the post-law period.

Conclusions: Rates of head injuries and deaths among motorcycle riders decreased significantly after implementation of the mandatory helmet law in Vietnam. To further examine the impact of the motorcycle helmet law, including compliance and helmet quality, further emphasis should be placed on gathering helmet use data from injured motorcyclists.     

Design,Modelling and Assessment of Emission Scenarios Resulting from a Network of Wood Biomass Boilers

The use of wood biomass as a fuel for domestic and industrial heating systems allows for a reduction of CO₂ emissions at a global scale, but it may also result in worse local air quality conditions, due to their emissions of particulate matter. The aim of this study is to assess the actual trend of atmospheric pollution in a study area, assuming that all heating systems are replaced by small size biomass boilers linked to the buildings through district heating network. Ground level concentrations of particulate matter, emitted by different heating systems, are therefore evaluated through numerical simulations performed by means of an atmospheric dispersion model (Sirane). As a first step, we have compared the environmental impact of a woodchip boilers network with that given by the use of traditional heating systems, i.e. wood stoves and natural gas boilers. As a second step, we have analysed the impact of such a network taking into account different emission scenarios, related to different boilers operating conditions. Results show that the environmental performances of a woodchip boilers network can be optimized by combining it with other renewable sources of energy devoted to the supply of hot water. The adopted analysis methodology can be applied to other real or hypothetic punctual sources on the territory.     

Bioconcentration and half-life of quinalphos pesticide in rice-fish integration system in the Mekong Delta,Vietnam

In order to determine the distribution and enable the elimination of quinalphos, a popular active pesticide compound used in the Mekong Delta, an experiment was set up in a rice-fish integration system in Can Tho City, Vietnam. Fish was stocked into the field when the rice was two-months old. Quinalphos was applied twice in doses of 42.5 g per 1000 m². Water, fish and sediment samples were collected at time intervals and analyzed by a Gas Chromatography Electron Capture Detector system. The results show that quinalphos residues in fish muscles were much higher than those of the water and the bioconcentration factor (logBCF) was above 2 for the fish. The half-life of first and second quinalphos applications were 12.2 and 11.1 days for sediment, 2.5 and 1.1 days for silver barb, 1.9 and 1.3 days for common carp, and 1.1 and 1.0 days for water, respectively.