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271.
This paper situates livelihood adaptations in two coastal villages within the broader context of Belize's colonial and post-colonial history and environmental processes of change. Through observations, qualitative interviews, and archival reviews, we explore the dynamics of livelihood change and analyse the diverse factors that have been influencing options and adaptation over time. The results reveal that both villages have undergone profound changes in livelihoods and productive activities on several occasions. While the villages' histories, geographies, and cultures are different, similarities in long-term trends include the transition from land-based to marine resources and the decline of small-scale agriculture. Our analysis illuminates the deep connections between local livelihoods and national as well as global political–economic processes, which favour extraction and export of natural resources throughout the period investigated, whereby resource access and market mechanisms create and constrict adaptation options for the villagers. Gradual environmental changes, such as erosion, and episodic events, such as hurricanes, have also influenced livelihood shifts and adaptations in combination with a wide range of political–economic factors. Despite the demonstrated importance of the influence of history and dimensions of political economy on contemporary adaptation options in the communities studied, the literature on climate change adaptation inadequately accounts for these factors. This paper adds new perspectives to current debates in climate change research by emphasising that longer temporal dimensions of livelihood change are important for understanding the current context for adaptation. 相似文献
272.
Public parks are important to urban environments, residents, and visitors. Among other functions, they provide environmental services, such as air and water purification, and they increase both recreational opportunities and the attractiveness of the urban environment. Because of their importance, urban parks serve as public spaces that provide visitors and urban residents with rights to the city. This paper identifies the dearth of urban public parks in Accra-Tema city-region as worrying. The Accra Plan 1958 underscored the significance of green spaces and designated the coastal strip for parks development but the areas have been lost to various urban uses. We argue that the continual neglect of public parks within urban planning and community development schemes in the Accra-Tema city-region is a major concern because it is depriving the citizens a right to the city and its public spaces. A number of factors have worked adversely against the provision of public parks and green spaces in the city-region. These include development pressures, undue political interference, a complex land delivery system, and ad hoc planning. The paper concludes by offering policy suggestions as to how to resolve the dearth of parks and green spaces in the city-region. 相似文献
273.
Christian Natale Gencarelli Francesco De Simone Ian Michael Hedgecock Francesca Sprovieri Nicola Pirrone 《Environmental science and pollution research international》2014,21(6):4095-4109
The emission, transport, deposition and eventual fate of mercury (Hg) in the Mediterranean area has been studied using a modified version of the Weather Research and Forecasting model coupled with Chemistry (WRF/Chem). This model version has been developed specifically with the aim to simulate the atmospheric processes determining atmospheric Hg emissions, concentrations and deposition online at high spatial resolution. For this purpose, the gas phase chemistry of Hg and a parametrised representation of atmospheric Hg aqueous chemistry have been added to the regional acid deposition model version 2 chemical mechanism in WRF/Chem. Anthropogenic mercury emissions from the Arctic Monitoring and Assessment Programme included in the emissions preprocessor, mercury evasion from the sea surface and Hg released from biomass burning have also been included. Dry and wet deposition processes for Hg have been implemented. The model has been tested for the whole of 2009 using measurements of total gaseous mercury from the European Monitoring and Evaluation Programme monitoring network. Speciated measurement data of atmospheric elemental Hg, gaseous oxidised Hg and Hg associated with particulate matter, from a Mediterranean oceanographic campaign (June 2009), has permitted the model’s ability to simulate the atmospheric redox chemistry of Hg to be assessed. The model results highlight the importance of both the boundary conditions employed and the accuracy of the mercury speciation in the emission database. The model has permitted the reevaluation of the deposition to, and the emission from, the Mediterranean Sea. In light of the well-known high concentrations of methylmercury in a number of Mediterranean fish species, this information is important in establishing the mass balance of Hg for the Mediterranean Sea. The model results support the idea that the Mediterranean Sea is a net source of Hg to the atmosphere and suggest that the net flux is ≈30 Mg year?1 of elemental Hg. 相似文献
274.
Life cycle assessment (LCA) has developed into a useful methodology to assess energy consumption of fishing fleets and their derived seafood products, as well as the associated environmental burdens. In this study, however, the life cycle inventory data is used to provide a dimensionless ratio between energy inputs and the energy provided by the fish: the edible protein energy return on investment (ep-EROI). The main objective was to perform a critical comparison of seafood products landed in Galicia (NW Spain) in terms of ep-EROI. The combination of energy return on investment (EROI) with LCA, the latter having standardized mechanisms regarding data acquisition and system boundary delimitation, allowed a reduction of uncertainties in EROI estimations. Results allow a deeper understanding of the energy efficiency in the Galician fishing sector, showing that small pelagic species present the highest ep-EROI values if captured using specific fishing techniques. Finally, results are expected to provide useful guidelines for policy support in the EU’s Common Fisheries Policy.
Electronic supplementary material
The online version of this article (doi:10.1007/s13280-013-0426-2) contains supplementary material, which is available to authorized users. 相似文献275.
Hua Shen Miao Li Bingxuan Wang Ian K. Lai Larry W. Robertson Gabriele Ludewig 《Environmental science and pollution research international》2014,21(10):6384-6399
Environmental pollutants polychlorinated biphenyls (PCBs), especially dioxin-like PCBs, cause oxidative stress and associated toxic effects, including cancer and possibly atherosclerosis. We previously reported that PCB 126, the most potent dioxin-like PCB congener, not only decreases antioxidants such as hepatic selenium (Se), Se-dependent glutathione peroxidase, and glutathione (GSH) but also increases levels of the antiatherosclerosis enzyme paraoxonase 1 (PON1) in liver and serum. To probe the interconnection of these three antioxidant systems, Se, GSH, and PON1, we examined the influence of varying levels of dietary Se and N-acetylcysteine (NAC), a scavenger of reactive oxygen species (ROS) and precursor for GSH synthesis, on PON1 in the absence and presence of PCB 126 exposure. Male Sprague–Dawley rats, fed diets with differing Se levels (0.02, 0.2, or 2 ppm) or NAC (1 %), were treated with a single intraperitoneal injection of corn oil or various doses of PCB 126 and euthanized 2 weeks later. PCB 126 significantly increased liver PON1 mRNA, protein level and activity, and serum PON1 activity in all dietary groups but did not consistently increase thiobarbituric acid levels (thiobarbituric acid reactive substances, TBARS), an indicator of lipid oxidation and oxidative stress, in liver or serum. Inadequate (high or low) dietary Se decreased baseline and PCB 126-induced aryl hydrocarbon receptor (AhR) expression but further increased PCB 126-induced cytochrome P450 1A1 (CYP1A1) expression, the enzyme believed to be the cause for PCB 126-induced oxidative stress. In addition, a significant inverse relationship was observed not only between dietary Se levels and PON1 mRNA and PON1 activity but also with TBARS levels in the liver, suggesting significant antioxidant protection from dietary Se. NAC lowered serum baseline TBARS levels in controls and increased serum PON1 activity but lowered liver PON1 activities in animals treated with 1 μmol/kg PCB 126, suggesting antioxidant activity by NAC primarily in serum. These results also show an unexpected predominantly inverse relationship between Se or NAC and PON1 during control and PCB 126 exposure conditions. These interactions should be further explored in the development of dietary protection regimens. 相似文献
276.
Soil erosion and sediment fluxes analysis: a watershed study of the Ni Reservoir,Spotsylvania County,VA, USA 总被引:1,自引:0,他引:1
Anthropogenic forces that alter the physical landscape are known to cause significant soil erosion, which has negative impact on surface water bodies, such as rivers, lakes/reservoirs, and coastal zones, and thus sediment control has become one of the central aspects of catchment management planning. The revised universal soil loss equation empirical model, erosion pins, and isotopic sediment core analyses were used to evaluate watershed erosion, stream bank erosion, and reservoir sediment accumulation rates for Ni Reservoir, in central Virginia. Land-use and land cover seems to be dominant control in watershed soil erosion, with barren land and human-disturbed areas contributing the most sediment, and forest and herbaceous areas contributing the least. Results show a 7 % increase in human development from 2001 (14 %) to 2009 (21.6 %), corresponding to an increase in soil loss of 0.82 Mg ha-1 year-1 in the same time period. 210Pb-based sediment accumulation rates at three locations in Ni Reservoir were 1.020, 0.364, and 0.543 g cm-2 year-1 respectively, indicating that sediment accumulation and distribution in the reservoir is influenced by reservoir configuration and significant contributions from bedload. All three locations indicate an increase in modern sediment accumulation rates. Erosion pin results show variability in stream bank erosion with values ranging from 4.7 to 11.3 cm year-1. These results indicate that urban growth and the decline in vegetative cover has increased sediment fluxes from the watershed and poses a significant threat to the long-term sustainability of the Ni Reservoir as urbanization continues to increase. 相似文献
277.
Correspondence of biological condition models of California streams at statewide and regional scales
Jason T. May Larry R. Brown Andrew C. Rehn Ian R. Waite Peter R. Ode Raphael D. Mazor Kenneth C. Schiff 《Environmental monitoring and assessment》2015,187(1):1-21
We used boosted regression trees (BRT) to model stream biological condition as measured by benthic macroinvertebrate taxonomic completeness, the ratio of observed to expected (O/E) taxa. Models were developed with and without exclusion of rare taxa at a site. BRT models are robust, requiring few assumptions compared with traditional modeling techniques such as multiple linear regression. The BRT models were constructed to provide baseline support to stressor delineation by identifying natural physiographic and human land use gradients affecting stream biological condition statewide and for eight ecological regions within the state, as part of the development of numerical biological objectives for California’s wadeable streams. Regions were defined on the basis of ecological, hydrologic, and jurisdictional factors and roughly corresponded with ecoregions. Physiographic and land use variables were derived from geographic information system coverages. The model for the entire state (n?=?1,386) identified a composite measure of anthropogenic disturbance (the sum of urban, agricultural, and unmanaged roadside vegetation land cover) within the local watershed as the most important variable, explaining 56 % of the variance in O/E values. Models for individual regions explained between 51 and 84 % of the variance in O/E values. Measures of human disturbance were important in the three coastal regions. In the South Coast and Coastal Chaparral, local watershed measures of urbanization were the most important variables related to biological condition, while in the North Coast the composite measure of human disturbance at the watershed scale was most important. In the two mountain regions, natural gradients were most important, including slope, precipitation, and temperature. The remaining three regions had relatively small sample sizes (n?≤?75 sites) and had models that gave mixed results. Understanding the spatial scale at which land use and land cover affect taxonomic completeness is imperative for sound management. Our results suggest that invertebrate taxonomic completeness is affected by human disturbance at the statewide and regional levels, with some differences among regions in the importance of natural gradients and types of human disturbance. The construction and application of models similar to the ones presented here could be useful in the planning and prioritization of actions for protection and conservation of biodiversity in California streams. 相似文献
278.
279.
Sexual dimorphism has been linked to parasitoid mating structure by several authors. In turn mating structure has an important
influence on predicted sex ratio optima. Here we test the relationship between sexual dimorphism and sex ratio using data
from 19 species of bethylid wasps. Using phylogenetically based comparative methods we confirm the findings of a previous
cross-species analysis that sex ratio (proportion of males) is strongly and negatively correlated with clutch size. Using
cross-species comparisons we show an additional positive correlation of sex ratio and relative male size, as predicted. The
relationship however is not significant when using phylogenetically based methods. The cross-species result is largely due
to differences between two bethylid sub-families: the Epyrinae have relatively large males and relatively high sex ratios,
whereas the Bethylinae have relatively small males and lower sex ratios. Our study illustrates the benefits and drawbacks
of using cross-species versus phylogenetically based comparisons.
Received: 13 May 1997 / Accepted after revision: 12 January 1998 相似文献
280.
Shen L Gewurtz SB Reiner EJ MacPherson KA Kolic TM Helm PA Brindle ID Marvin CH 《Environmental pollution (Barking, Essex : 1987)》2008,156(2):515-525
This study determines spatial trends and congener patterns of 2378-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in surficial sediments of Lakes Erie and Ontario. Sediments are enriched in 2378-PCDFs in Lake Ontario, and the PCDD/F concentrations increased from shallow near-shore sediments towards deep-water depositional zone sediments. In Lake Erie, sediments were dominated by octachlorodibenzo-p-dioxin, and the highest PCDD/F concentrations were observed in the western basin and the southern shoreline of the central basin with a decrease towards the eastern basin and the northern shoreline of the central basin. Principal components analysis revealed that chemical manufacture and disposal of chemical waste along the Niagara River has been a major PCDD/F source to Lake Ontario; while PCDD/Fs in Lake Erie are from multiple sources including industrial sources along the Detroit River, major tributaries along the southern shoreline of the lake, and atmospherically-derived material from the upper lakes and connecting channels. 相似文献