Pollution and Genetic Structure of North American Populations of the Common Dandelion (Taraxacum Officinale)

Assessing the genetic structure of natural populations differentially impacted by anthropogenic contaminants can be a useful tool for evaluating the population genetic consequences of exposure to pollution. In this study, measures of genetic diversity at variable-number-tandem-repeat loci in six dandelion populations (3 urban and 3 rural) showed patterns that may have been influenced by exposure to environmental contaminants. Mean genetic similarity among individuals within a population was significantly and positively correlated with increasing levels of airborne particulate matter ( 10 m, PM₁₀) and soil concentrations of four metals (Cd, Fe, Ni and Pb). In addition, mean genetic similarity was always significantly higher at the urban sites compared to rural sites. There was a significant negative correlation between the number of genotypes at a site and increasing amounts of PM₁₀, concentrations of five soil metals (Cd, Cu, Fe, Ni and Pb), leaf tissue levels of Fe and a significant positive correlation between the extent of clonality at a site and levels of PM₁₀ and soil concentrations of five metals (Cd, Cu, Fe, Ni and Pb). Although, this study does not directly establish a causal link between the specific contaminants detected at the study sites and differences in genetic diversity, our data are consistent with the hypothesis that pollution-induced selection has contributed in some fashion to the lower genetic diversity found at the urban sites.     

Linking multimetric and multivariate approaches to assess the ecological condition of streams

Few attempts have been made to combine multimetric and multivariate analyses for bioassessment despite recognition that an integrated method could yield powerful tools for bioassessment. An approach is described that integrates eight macroinvertebrate community metrics into a Principal Components Analysis to develop a Multivariate Condition Score (MCS) from a calibration dataset of 511 samples. The MCS is compared to an Index of Biotic Integrity (IBI) derived using the same metrics based on the ratio to the reference site mean. Both approaches were highly correlated although the MCS appeared to offer greater potential for discriminating a wider range of impaired conditions. Both the MCS and IBI displayed low temporal variability within reference sites, and were able to distinguish between reference conditions and low levels of catchment modification and local habitat degradation, although neither discriminated among three levels of low impact. Pseudosamples developed to test the response of the metric aggregation approaches to organic enrichment, urban, mining, pastoral and logging stressor scenarios ranked pressures in the same order, but the MCS provided a lower score for the urban scenario and a higher score for the pastoral scenario. The MCS was calculated for an independent test dataset of urban and reference sites, and yielded similar results to the IBI. Although both methods performed comparably, the MCS approach may have some advantages because it removes the subjectivity of assigning thresholds for scoring biological condition, and it appears to discriminate a wider range of degraded conditions.     

Distinctive types of leaf tissue damage influence nutrient supply to growing tissues within seagrass shoots

Herbivory is now recognized as an important structuring agent in seagrass meadows but the attack pattern and tissue damage of consumers are highly variable. Nutritional preferences of herbivores and/or easy access to resources may cause differences in biomass loss among tissues that damage the plant in functionally distinctive ways. The two main Mediterranean herbivores, the fish Sarpa salpa (L.) and the sea urchin Paracentrotus lividus (Lmk.), remove higher amounts of intermediate and external shoot leaves, respectively. To test whether this selective feeding can have different consequences on the allocation patterns of nutrient within plants, we simulated the effect of both herbivores by clipping external and intermediate leaves (plus unclipped controls) of Posidonia oceanica (L.) and we measured plant tolerance in terms of shoot growth and leaf nutrient supply to new tissue using isotopic markers. As expected, control treatments displayed high carbon and nutrient supply from external leaves (83% of the total ¹⁵N and 84% of the total ¹³C incorporated by the shoot). When subjected to clipping, the remaining leaves enhanced carbon and nitrogen supply compared with the control by 16% of N and 36% of C—in the intermediate clipping—and by over 100% of N and 200% of C—in the external clipping—to compensate for the nutrient lost. However, only in the case of fish herbivory (intermediate clipping), enhanced supply alone was able to fully compensate for the nutrient losses. In contrast, this mechanism is not completely effective when external leaves are clipped (urchin herbivory). Yet, the consequences of this nutrient loss under sea urchin herbivory are not apparent from the nutrient content of the new tissue, suggesting that there are other sources of nitrogen income (uptake or reallocation from rhizomes). Our study does not only confirm the tolerance of P. oceanica to herbivory, but also constitutes the first evidence of leaf-specific, compensatory nutrient supply in seagrasses.     

Sustainable roofing technology under multiple constraints: a decision-analytical approach

Recent efforts in the private and public sectors to move toward enhanced sustainability in the built environment have prompted the need to quantify and assess trade-offs among relevant sustainability metrics. Within the US military, for instance, many technological improvements are available to facilitate the achievement of net-zero goals for installations. These technologies must be assessed based on numerous performance criteria, and these technology selection decisions are difficult to make unaided. This paper seeks to demonstrate the use of decision-analytical techniques in which sustainable roofing technology alternatives (reflective, vegetated, or solar roofs) can be properly framed and assessed while evaluating the trade-offs between multiple performance criteria. Multi-criteria decision analysis methods are used to assess the impact of technology alternatives on sustainability framed within the popular concept of the triple bottom line (economic, societal, and environmental concerns). The framework developed in this paper can be applied to other sustainability technologies (energy, water, waste) or portfolios of numerous technologies.     

Local authorities and climate protection in the European union: Putting subsidiarity into practice?

Abstract

Although intrinsically a global environmental concern, the climate change issue has a number of implications for local authorities. Within the European Union (EU), the remit of local authorities in—‐for abatement policies—the crucial areas of energy and transport policy varies considerably, as does their commitment to environmental action more generally. This paper examines the role of local authorities in climate protection within a framework of global, EU and national action, through examples of local strategies from Germany, Italy, Spain, Sweden and the UK. The paper finds positive instances of action in all countries, but points to unsympathetic policy frameworks both at national and EU level, such as budget constraints imposed on local authorities, the pursuit of low energy prices combined with a resistance to impose carbon taxes, a lack of energy efficiency standards and insufficient support for public transport.