The reconstruction of environmental rights in urban South Africa

Rapid and spatially concentrated urbanization in South Africa has brought with it significant health and safety hazards. These hazards are described and analyzed through two optics: environmental rights and community participation. The rights perspective suggests that the system of apartheid led to a collapse of rural livelihoods, driving people to the cities, while apartheid's tight control over African residential location and employment ensured that high density settlement and unemployment would follow. The resulting urban environmental degradation and health and safety hazards are a violation of the human rights of the African residents of townships and informal settlements. The community participation perspective suggests that reconstruction can be linked to development and that community-based hazard identification and mitigation can be a vehicle for kick-starting urban revitalization.     

Invertebrate traits for the biomonitoring of large European rivers: an assessment of specific types of human impact

1. The power of selected biological invertebrate traits for discriminating different types of human impact (heavy metal pollution and cargo‐ship traffic) were tested using ecological reasoning and linear Discriminant Function Analysis (DFA). 2. Frequency distributions of individual traits and categories of traits from 68 least impacted river reaches (LIRRs) and 304 impacted river reaches were used to define simple assessment rules based on ecological reasoning for specific impairments in large European rivers. In calibration, a maximum of three variables with a priori predictions and two different impairment threshold levels were used. Similarly, DFA was performed on the same variables included in the ecological reasoning approach, but also on all available traits or trait categories. 3. Validation with an independent data set (40 LIRRs, 291 variously impacted river reaches) and using the ecological reasoning approach showed that 75–78% of the reaches were correctly assign with rules on all impact types, 35–57% with rules on heavy metal pollution and 78–93% with rules on cargo‐ship traffic. By comparison, validation showed that DFA performed globally poorer than the ecological reasoning approach. In addition, the performance of the rules based on ecological reasoning remained stable, whereas DFA performance changed between calibration and validation. 4. Although not defined for this purpose, our study provided alarming evidence regarding the impact of cargo‐ship traffic on invertebrate communities in river reaches. Reaches with cargo‐ship traffic were found to have more genera with long life cycles that reproduce repeatedly by ovoviviparity and have a sessile life. 5. The performance of our trait‐based approach to correctly assign reaches to either least impacted or impacted conditions should promote further research on the topic across larger geographic areas (without regionalization) and across smaller stream types to provide a powerful biomonitoring tool that fulfils current European Union directives.     

Pollution-Tolerant Species and Communities: Intriguing Toys or Invaluable Monitoring Tools?

Luoma suggested 25 years ago that tolerant populations could be used to detect adverse ecological effects of pollution. Despite the apparent attractiveness of the idea, there have been few successful examples of its use and a number of failures. Pollution-tolerant populations are limited almost entirely to areas that are grossly contaminated with one or a small number of substances and have flora and fauna that are severely impoverished. Tolerance does provide strong evidence of impact by a particular contaminant but is of limited value as a monitoring tool. Instances of evolved tolerance do, however, have a valuable role to play in environmental risk assessment. They provide model systems for understanding the impact of pollutants on the physiology and performance of individuals and in consequence how they produce effects at the population and community level, in the way that metal tolerance in plants has been used as a model system for the study of evolution. Pollution-induced community tolerance has more promise than population tolerance as a tool for monitoring the effects of pollution, and already has a much longer list of successful applications despite its shorter history.     

城市化过程对河道系统的干扰与生态修复原则和方法

城市化快速发展在带来大量工业和生活污水的同时,对自然生态系统的干扰也打破了原来生态系统的结构和平衡,由此带来的生态环境影响已经引起人们的高度重视。本文系统分析了城市化过程对河道系统的干扰类型、特征,影响河道生态系统健康的关键过程和河道系统生态修复的基本原则和发展方向。认为城市河道系统受到的干扰主要体现在结构固结化、形态规整化和功能简单化3方面;影响河道生态系统健康的关键过程可归纳为3方面:物质交换通道的阻隔、生物栖息环境的破坏和河道生态水文过程的失衡。指出河道系统的生态修复应该遵循以下6个原则:1)道法自然原则;2)功能引导原则;3)时空尺度分异原则;4)生态循环与平衡原则;5)利益相关者参与原则;6)综合效益最优原则。在此基础上,进一步分析了河道系统生态修复的时空尺度和生态修复的方法以及发展方向。     

Mycotoxin Reduction in Bt Corn: Potential Economic, Health, and Regulatory Impacts

Genetically modified (GM) Bt corn, through the pest protection that it confers, has lower levels of mycotoxins: toxic and carcinogenic chemicals produced as secondary metabolites of fungi that colonize crops. In some cases, the reduction of mycotoxins afforded by Bt corn is significant enough to have an economic impact, both in terms of domestic markets and international trade. In less developed countries where certain mycotoxins are significant contaminants of food, Bt corn adoption, by virtue of its mycotoxin reduction, may even improve human and animal health. This paper describes an integrated assessment model that analyzes the economic and health impacts of two mycotoxins in corn: fumonisin and aflatoxin. It was found that excessively strict standards of these two mycotoxins could result in global trade losses in the hundreds of millions $US annually, with the US, China, and Argentina suffering the greatest losses. The paper then discusses the evidence for Bt corn’s lower levels of contamination of fumonisin and aflatoxin, and estimates economic impacts in the United States. A total benefit of Bt corn’s reduction of fumonisin and aflatoxin in the US was estimated at $23 million annually. Finally, the paper examines the potential policy impacts of Bt corn’s mycotoxin reduction, on nations that are making a decision on whether to allow commercialization of this genetically modified crop.     

Human modification of the landscape and surface climate in the next fifty years

Human modification of the landscape potentially affects exchanges of energy and water between the terrestrial biosphere and the atmosphere. This study develops a possible scenario for land cover in the year 2050 based on results from the IMAGE 2 (Integrated Model to Assess the Greenhouse Effect) model, which projects land‐cover changes in response to demographic and economic activity. We use the land‐cover scenario as a surface boundary condition in a biophysically‐based land‐surface model coupled to a general circulation model for a 15‐years simulation with prescribed sea surface temperature and compare with a control run using current land cover. To assess the sensitivity of climate to anthropogenic land‐cover change relative to the sensitivity to decadal‐scale interannual variations in vegetation density, we also carry out two additional simulations using observed normalized difference vegetation index (NDVI) from relatively low (1982–83) and high (1989–90) years to describe the seasonal phenology of the vegetation. In the past several centuries, large‐scale land‐cover change occurred primarily in temperate latitudes through conversion of forests and grassland to highly productive cropland and pasture. Several studies in the literature indicate that past changes in surface climate resulting from this conversion had a cooling effect owing to changes in vegetation morphology (increased albedo). In contrast, this study indicates that future land‐cover change, likely to occur predominantly in the tropics and subtropics, has a warming effect governed by physiological rather than morphological mechanisms. The physiological mechanism is to reduce carbon assimilation and consequently latent relative to sensible heat flux resulting in surface temperature increases up to 2 °C and drier hydrologic conditions in locations where land cover was altered in the experiment. In addition, in contrast to an observed decrease in diurnal temperature range (DTR) over land expected with greenhouse warming, results here suggest that future land‐cover conversion in tropics could increase the DTR resulting from decreased evaporative cooling during the daytime. For grid cells with altered land cover, the sensitivity of surface temperature to future anthropogenic land‐cover change is generally within the range induced by decadal‐scale interannual variability in vegetation density in temperate latitudes but up to 1.5 °C warmer in the tropics.     

城市化对土壤环境的影响

城市化对土壤环境产生深刻的影响,城市污水灌溉、工业废气和汽车废气、城市生活垃圾等都会改变土壤的理化性质。防治土壤污染、改善城市土壤环境,必须工业合理布局,治理工业污染源,加强农业环境的监测等。