The Emergence of Gated Communities in a West African Context: Evidence From Greater Accra,Ghana     

《Urban geography》2013,34(8):661-683

Since the beginning of the 1990s, the global expansion of gated communities has become an increasingly important part of the residential geography of many cities. The gated community phenomenon has not been researched in West African cities, and the extent of these communities' formation and convergence or divergence with global trends is unknown. This article provides the first-ever analysis of their formation in Greater Accra, Ghana. The analysis suggests that the globalization of real estate markets and Diaspora living are important aspects in the residential geography of Accra. The concept of "transnational houses" is employed to explain aspects of the local property market that are being globalized and differentiated from local housing. Transnational houses add another layer of diversity to the contemporary urban geography of Greater Accra.  相似文献   

Memento Mori: The “Death” of Youngtown     

Kevin E. McHugh  Ann M. Fletchall 《The Professional geographer》2013,65(1):21-35

Youngtown, Arizona, was founded in 1954 as the nation's first retirement community, presaging the original Sun City (1960) and subsequent proliferation of active-adult communities across America. Youngtown, whose attractiveness waned owing to competition from more upscale, amenity-rich communities, suffered a fatal blow in 1998. Legal issues led to the loss of age restrictions, ushering in a swift and dramatic transformation of Youngtown from retirement enclave to working-class community, as Youngtown was overwhelmed by powerful social currents coursing through the Phoenix metropolitan region: explosive population growth, suburban sprawl, Latinization, and voracious demand for affordable housing. We tell the story of the life and death of Youngtown as a retirement haven, including the response of seniors to the loss in community identity: out-migration, anger, depression, and eventual acceptance among older people who linger. Insular, freeze-frame dreams of community identity and stability common among seniors in retirement enclaves ultimately prove chimerical in the face of urban change. The death of Youngtown as retiree haven, viewed in the sweep of shifting cultural attitudes about aging, may be a harbinger, the opening notes in a requiem for de jure retirement communities.  相似文献   

Sediment macrobenthos off eastern Waiheke Island,Hauraki Gulf,New Zealand     

KL Clara Wong  Steve O'Shea 《新西兰海洋与淡水研究杂志》2013,47(3):149-165

Aspects of sea-bed structure and benthic-macroinvertebrate species composition, distribution, richness and diversity in coastal waters off eastern Waiheke Island, Hauraki Gulf, are reported. In contrast to the sole historical account of sea-bed community structure from this same region, no widely distributed assemblages of species are recognised throughout it; no two sites share the exact same complement of species; and almost all sites are less than 80% similar in their taxonomic composition, most considerably so. Species richness and diversity are reported to vary with substratum type and depth, and spatially; species occurring within muds are the least diverse and species rich, followed by those of muddy gravels, and then gravels; many taxa prove common to the three substratum types; and dominance of taxa is recognised to decrease with an increase in substratum complexity, from muds to gravels, and species richness. With the exception of invasive marine species, apparent changes in the composition of assemblages throughout this region over the eight-decade period that data span are considered artefacts of the way in which such assemblages were historically defined. We recommend historical accounts of sea-bed community distributions throughout Hauraki Gulf be interpreted with caution, especially when attempting to use such schematic depictions to determine whether changes have occurred in assemblage composition.  相似文献   

Identifying fisheries dependent communities in EU coastal areas     

《Marine Policy》2013

The importance of local communities relying on fisheries is constantly emphasised in the European Union's Common Fishery Policy. Previous studies have analysed fishery employment for the entire EU based on statistical figures aggregated by administrative units at the regional or provincial level. This paper adopts a geographical approach to identify EU coastal communities relying on fisheries using accessibility analysis, principles at the basis of gravity models and disaggregated population and employment statistics. The dependency on fisheries is calculated comparing estimated employment from fisheries at each port with general employment in the areas of accessibility surrounding the port. By considering spatially disaggregated statistics the importance of fishing activities for specific local communities emerges more clearly in respect of previous studies. The map of fisheries dependent coastal communities identifies in 2010, 388 communities, out of 1697, with dependency ratios above 1%. Around 54% of total fishery employment is estimated in these areas. In terms of policy support, identifying and mapping these local fishing coastal communities is of key importance considering the strong priority assigned by the new European Union's Common Fishery Policy to fishery management at the regional level.  相似文献   

Environmental drivers of megafaunal assemblage composition and biomass distribution over mainland and insular slopes of the Balearic Basin (Western Mediterranean)     

《Deep Sea Research Part I: Oceanographic Research Papers》2013

The influence of mesoscale physical and trophic variables on deep-sea megafauna, a scale of variation often neglected in deep-sea studies, is crucial for understanding their role in the ecosystem. Drivers of megafaunal assemblage composition and biomass distribution have been investigated in two contrasting areas of the Balearic basin in the NW Mediterranean: on the mainland slope (Catalonian coasts) and on the insular slope (North of Mallorca, Balearic Islands). An experimental bottom trawl survey was carried out during summer 2010, at stations in both sub-areas located between 450 and 2200 m water depth. Environmental data were collected simultaneously: near-bottom physical parameters, and the elemental and isotopic composition of sediments. Initially, data were analysed along the whole depth gradient, and then assemblages from the two areas were compared. Analysis of the trawls showed the existence of one group associated with the upper slope (US=450–690 m), another with the middle slope (MS=1000–1300 m) and a third with the lower slope (LS=1400–2200 m). Also, significant differences in the assemblage composition were found between mainland and insular slopes at MS. Dominance by different species was evident when the two areas were compared by SIMPER analysis. The greatest fish biomass was recorded in both areas at 1000–1300 m, a zone linked to minimum temperature and maximum O₂ concentration on the bottom. Near the mainland, fish assemblages were best explained (43% of total variance, DISTLM analysis) by prey availability (gelatinous zooplankton biomass). On the insular slope, trophic webs seemed less complex and were based on vertical input of surface primary production. Decapods, which reached their highest biomass values on the upper slope, were correlated with salinity and temperature in both the areas. However, while hydrographic conditions (temperature and salinity) seemed to be the most important variables over the insular slope, resource availability (gelatinous zooplankton and Calocaris macandreae) predominated and explained 59% of decapod assemblage variation over the mainland slope. Both fish and decapods were linked to net primary production recorded over the mainland 3 months before sampling, while the delay between the input of food from the surface and fish abundance was only 1 month on the insular slope. Our results suggest that trophic relationships over insular slopes probably involve a shorter food chain than over mainland slopes and one that is likely more efficient in terms of energy transfer.  相似文献   

Influence of sample size on ecological status assessment using marine benthic invertebrate‐based indices     

Borut Mavrič  Gorazd Urbanič  Lovrenc Lipej  Nomiki Simboura 《Marine Ecology》2013,34(1):72-79

Routine monitoring of the quality status of water bodies demands the best cost‐benefit relation and sample‐size reduction is therefore welcomed. However, great caution is needed because such reduction affects the accuracy and variation of the results. In the present study we tested the influence of sample size (number of replicate samples) on reference condition values and within‐sample ecological quality ratio (EQR) variability of six commonly used ecological indices (taxa richness, Shannon–Wiener diversity, AMBI, Medocc index, Bentix and M‐AMBI). Analysis of soft‐bottom benthic invertebrate data from Slovenian coastal waters showed that sample size influenced the reference condition values of richness/diversity indices (taxa richness and Shannon–Wiener diversity) but not of the sensitivity/tolerance indices (AMBI, Medocc index, Bentix). Increased sample size decreased the within‐sample EQR variability and, concomitantly, increased the accuracy of site ecological status classification for all indices. The size of EQR variability differed depending on the index used. EQR variability of M‐AMBI, an index composed of metrics with different within‐sample EQR variability, was statistically the same as that of the metric with the lowest within‐sample EQR variability. Whether this is a common principle for multimetric indices remains to be confirmed. Based on these results, the use of at least three replicates is suggested to obtain reliable measures of reference condition and EQR for the assessment of ecological status. This level of replication is particularly necessary in areas with high diversity and environmental patchiness, and when richness/diversity measures and indices that include these measures are used.  相似文献   

Responses of benthic macrofauna and biogeochemical fluxes to various levels of mussel biodeposition: An in situ “benthocosm” experiment     

Myriam D. Callier  Marion Richard  Christopher W. McKindsey  Philippe Archambault 《Marine pollution bulletin》2009,58(10):1544-1553

An in situ experiment was done to evaluate the dose-dependent response of mussel biodeposition on benthic communities and biogeochemical fluxes. Natural benthic communities were exposed to 7 different levels of mussel biodeposition (equivalent to that produced by 0-764 mussels m⁻²) over 50 days. Benthic communities responded as predicted from the Pearson, T.H., Rosenberg, R., 1978. Macrobenthic succession in relation to organic enrichment and pollution of the marine environment. Oceanogr. Mar. Biol. Annu. Rev. 16, 229-311 model of organic enrichment. Total abundance and species richness decreased with increasing biodeposition. The abundance and biomass of opportunistic species (Capitella spp.) increased in the mesocosms subject to the greatest biodeposition. Sensitive species Tellina agilis and Pherusa plumosa tended to decrease in abundance and biomass with increasing biodeposition. The biotic index M-AMBI responded clearly to increased biodeposition and may be a useful tool for assessing the effect of mussel biodeposition on the benthic environment. These results are important for the construction of predictive models for determining environmental carrying capacity for bivalve aquaculture.  相似文献   

Responses of Ruderal Verbascum olympicum Boiss. (Scrophulariaceae) Growing under Cadmium Stress          下载免费PDF全文

Hülya Arslan  Gürcan Güleryüz  Ayşegül Akpınar  Serap Kırmızı  Ümran Seven Erdemir  Şeref Güçer 《洁净——土壤、空气、水》2014,42(6):824-835

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贵州关岭县喀斯特峰丛石漠区苔藓群落生态特征   总被引：8，自引：6，他引：2  

张天汉  代玉  王智慧  张朝晖 《中国岩溶》2014,33(2):192-200

为了了解喀斯特峰丛石漠化区苔藓植物的种类和群落特征,本文选取贵州省安顺市关岭县喀斯特峰丛石漠化区的三种典型生境（裸地、人工植被和自然植被）,对苔藓植物进行样地调查,并利用种间相遇几率（PIE）、生态优势度、Shaanon-Wiener信息指数(衡量生态位宽度)和Morisita-Horn指数(衡量生态位重叠)来分析该区苔藓植物群落的组成、分布规律及生态特征。结果表明:（1）该区苔藓植物共有11科17属22种,真藓科为优势科,苔藓植物群落有19个类型。（2）苔藓群落PIE值与植被覆盖度呈正比,与岩石裸露率呈反比,自然植被生境的苔藓群落PIE值高于人工植被和裸地生境,但研究区苔藓群落PIE总体偏低,反映了喀斯特峰丛地区恶劣的生境条件。（3）研究区内卷叶湿地藓群落(Hyophiletum)、直蒴卷柏藓群落(Racopietum)和皱叶牛舌藓群落(Anomodetum)有着较高的生态优势度和生态位宽度,并且与其它苔藓群落的生态位重叠值很高。表明这三种苔藓群落对不同类型的峰丛石漠化生境都有着较好的适应能力,能够很好地与其它苔藓群落互利共生。   相似文献   

Impact evaluation of a fisheries development project     

《Marine Policy》2017

A number of fisheries development projects are undertaken every year in recognition of the important role fisheries play in many coastal communities. The objectives vary, but typically go beyond a limited focus on fisheries management and the ecosystem. This makes it difficult to evaluate the contribution of a project, particularly in data poor environments such as most developing countries. This paper used the recently developed Fisheries Performance Indicators (FPIs) to evaluate the impact of a World Bank development project in a Liberian coastal community. FPIs are designed to capture economic and social performance of a fisheries system in addition to the management and environmental impacts. The results show improvements in most ecological dimensions, and also in many social and economic dimensions targeted by the project. Hence, the project intervention appears to be positive. However, some indicators, particularly in relation to general governance in Liberia, showed a negative development which was not caused by the project.  相似文献