Industrial transformation and shrimp aquaculture in Thailand and Vietnam: pathways to ecological,social, and economic sustainability?

Shrimp aquaculture in Vietnam is in the process of being transformed into a major industry around the intensification of the production system. The experiences of other countries in the region, especially in Thailand where high input production systems dominate, suggests that now is a critical time for intervention to redirect industry into pathways that are more sustainable ecologically, socially, and economically. In Thailand, years of experience with intensified systems and a complex industrial organization has not led to sustainable solutions. The challenge here is for society to regain control and then to redirect the transformation along more efficient and benign pathways. Our analyses suggest that current pathways in both countries are unlikely to lead to a sustainable industry. A complete transformation of the way shrimp are grown, fed, processed, distributed, and regulated is needed.     

Land Cover Changes Between 1968 and 2003 In Cai Nuoc,Ca Mau Peninsula,Vietnam

Since 2000, the shrimp industry expands at a fast rate in the coastal areas of the Mekong Delta, Vietnam. Shrimp farming is known for its negative impact on the coastal environment. However, other human interventions like agriculture and urbanization also deteriorate the coastal environment. The land cover changes between 1968 and 2003 were determined and analyzed for the Cai Nuoc district, Ca Mau Province, Vietnam, using photos from 1968, 1992 (aerial photographs), 1997/98 (Spot) and 2003 (Landsat). It was clear that the district underwent serious land cover changes: deforestation between 1968 and 1992, with a simultaneous increase in rice land; a rapid decline in rice acreage from 1997 onwards, and, simultaneously, a blitz-increase in shrimp farming area. The forest area declined by 75% between 1968 and 2003. About 40% of this loss could be attributed to shrimp farming, while the remaining 60% was attributed to needs for agricultural land. Still, at present, shrimp farming is the major source of mangrove loss in the district. In 1999 shrimp farms covered 6.374 ha, in 2000 they covered 61.049 ha of the Cai Nuoc area. The swap from rice cultivation to shrimp farming was most-probably driven by households’ hopes for a higher income. It must be feared that the shrimp industry will have a negative impact on the environment (e.g. salinization) and on the livelihood of the district’s households. In 1968 saline water covered 219.9 km², in 1992, 1997/98 and 2003 the saline surface water area covered 92.4, 135.2 and 835.0 km², respectively. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

WATER ALLOCATION POLICY MODELING FOR THE DONG NAI RIVER BASIN: AN INTEGRATED PERSPECTIVE1

Abstract: Recent water sector reforms and increased scarcity and vulnerability of water resources, combined with declining public funding available for large scale infrastructure investment in the sector, have led to a greater awareness by the Government of Vietnam for the need to analyze water resource allocation and use in an integrated fashion, at the basin scale, and from a perspective of economic efficiency. In this study we focus on the development, application, and selected policy analyses using an integrated economic hydrologic river basin model for the Dong Nai River Basin in southern Vietnam. The model framework depicts the sectoral structure and location of water users (agriculture, industry, hydropower, domestic, and the environment) and the institutions for water allocation in the basin. Water benefit functions are developed for the major water uses subject to physical limitations and to constraints of system control and policy. Based on this modeling framework, we will analyze policies that can affect water allocation and use at the basin level, including both basin-specific and general macroeconomic policies.     

Optimal resource extraction contract with adverse selection

This paper studies the design of a mining concession contract as a multi-period adverse selection problem where production is the depletion of a non renewable resource. Compared with symmetric information, we show that overproduction is optimal in the terminal phase of the resource extraction program. Moreover, asymmetric information lengthens the contract duration but reduces the scarcity rent.     

一种紫外-可见光谱检测水质COD预测模型优化方法

针对紫外-可见光谱法检测水质COD预测模型的精度低和收敛速度慢等问题,研究了一种基于粒子群算法联合最小二乘支持向量机(PSO_LSSVM)的水质检测COD预测模型优化方法,并引入主元分析(PCA)算法对模型输入光谱数据进行降维预处理,借以提高模型的收敛速度.结果表明,利用粒子群(PSO)算法收敛速度快和全局优化能力,优化了最小二乘支持向量机(LSSVM)模型的惩罚因子和核函数参数,避免了人为选择参数的盲目性,克服了传统LSSVM预测模型的精度较低、稳健性较差等缺点.通过以收敛时间、预测平均相对误差(MRE)和均方根误差(RMSE)为评价标准进行评估,输入样本经过PCA降维预处理的PSO_LSSVM模型的预测能力和输入样本未经过降维预处理的LSSVM模型与PSO_LSSVM模型进行了比较分析,输入样本经过PCA降维预处理的PSO_LSSVM模型预测效果最优,且此算法使用C语言实现,易于移植,这为紫外-可见光谱水质COD在线、实时性检测奠定了基础.     

How application of agricultural waste can enhance soil health in soils acidified by tea cultivation: a review

Environmental Chemistry Letters - Tea is one of the world’s most consumed beverages and an important crop of many developing countries. Intensive tea cultivation has negative impacts on soil...     

Lab-on-a-chip technologies for food safety,processing, and packaging applications: a review

Environmental Chemistry Letters - The advent of microfluidic systems has led to significant developments in lab-on-a-chip devices integrating several functions onto a single platform. Over the...     

Methods for chemical conversion of plastic wastes into fuels and chemicals. A review

Plastics are utilized in various materials that are useful in everyday life. As the usage of plastics increases, the disposal of plastic materials has become a major issue, calling for recycling methods. Here, we review the different methods to recycle plastics, with focus on catalytic cracking. We present catalysts, cracking mechanisms, and we compare the various treatment methodologies. Several attempts were made by researchers to increase the efficiency of the cracking process using different catalysts and reactors. Many studies reveal high quality products are obtained by catalytic cracking, which consumes low energy and produces lesser residues when compared to other treatment technologies.

     

Chemical,physical and biological methods to convert lignocellulosic waste into value-added products. A review

Environmental Chemistry Letters - Actual agricultural practices produce about 998 million tonnes of agricultural waste per year. Therefore, converting lignocellulosic wastes into energy, chemicals,...