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941.
INTRODUCTION: The significance of the influence of poor pavement skid resistance values on accident frequency in wet pavement conditions has been the object of many studies over several years. The various investigations have produced very diverse findings. Only seldom, however, has detailed consideration been given to the central question of whether pavement skid resistance is a decisive parameter in the occurrence of local accident "black spots." Until now, the focus has been more on describing a relationship between pavement skid resistance and accident frequency. METHOD AND RESULTS: In the course of the network-wide survey of the states of pavements and of accident occurrence on Switzerland's freeways from 1999 to 2003, it emerged that a relationship with inadequate pavement skid resistance was provable for only a small proportion of accident black spots. These findings were used to frame a guideline for authorities and highway operators about how to treat skid resistance when assessing pavements and accident occurrence on freeways.  相似文献   
942.
This paper reviews recent research into the impact of recreation and tourism in protected areas on plant biodiversity and vegetation communities in Australia. Despite the international significance of the Australian flora and increasing visitation to protected areas there has been limited research on recreational and tourism impacts in Australia. As overseas, there are obvious direct impacts of recreation and tourism such as clearing of vegetation for infrastructure or damage from trampling, horse riding, mountain biking and off road vehicles. As well, there are less obvious but potentially more severe indirect impacts. This includes self-propagating impacts associated with the spread of some weeds from trails and roads. It also includes the severe impact on native vegetation, including many rare and threatened plants, from spread of the root rot fungus Phytopthora cinnamomi. This review highlights the need for more recreational ecology research in Australia.  相似文献   
943.
杨青利 《四川环境》2005,24(3):47-48,51
本文从水、气、固体废物、噪音四个方面详述了临潼区环境污染现状,分析污染产生的原因,结合临潼区社会经济发展,预测该区污染发展趋势,提出控制污染的措施。  相似文献   
944.
中国农村贫困的测度与模拟:1995-2003   总被引:3,自引:0,他引:3  
本文介绍了基予GQ Lorenz曲线的参数方法测度贫困的基本原理,测算了1995—2003年中国农村贫困状况,重点对贫困的变化进行模拟分析。不同贫困线的模拟分析表明:各贫困指标对贫困线较小的移动具有较商的敏感性,其政策涵义是扶贫不应当只注意贫困线以下的家庭。而且也应当注意陷入贫困风险商的家庭。贫困分解的模拟分析表明:不仅收入与贫困发生率有关,而且分配不合理却增加了贫困的深度和强度,其政策涵义是贫困问题的根本解决应将更多的注意力放在贫困人口的收入及其分配上。  相似文献   
945.
Abstract:  An important question in conservation biology is the extent to which the number of taxonomic supraspecific categories can serve as surrogates of species richness. This issue has been little explored in highly diverse areas. We used 113 floristic inventories from throughout Mexico, a megadiverse country, to evaluate the potential of higher-taxon richness for predicting local species richness of vascular plants. This large biodiversity data set includes the main vegetation types found across the country. In all, 247 families, 2,398 genera, and 11,890 species were used for the analysis, representing 99.6%, 90.2%, and 53.2% of the respective totals recorded in the country. We hypothesized that the number of genera and species would be accurately predicted by the richness of the higher taxon. To avoid getting spurious regressions resulting from the logical increase in lower-taxon richness as a higher taxon becomes richer, we calculated new response variables by subtracting from the number of elements in the lower taxon group the number of those in the higher taxon; these variables were "excess species" (number of species minus number of genera or families) and "excess genera" (number of genera minus number of families). Our results indicate that genera provide very effective surrogates for estimation of local species richness ( R 2= 0.85), whereas families have a more limited potential for this purpose ( R 2= 0.64). The predictive capacity of the diversity of higher taxon increased when the analyses were constrained to particular vegetation types (maximum R 2= 0.95 for genera). This surrogate method may be a valuable tool in locating and designing representative systems of protected areas for vascular plant diversity, especially in megadiverse countries, where conservation efforts are hindered by the lack of complete inventories and insufficient resources.  相似文献   
946.
Tendencies in plant cover synanthropization depending on the pattern and intensity of anthropogenic impacts on natural complexes have been revealed in specially protected areas of different classes (a nature reserve and a nature park).  相似文献   
947.
在当前经济全球化日益加速的时代背景下.江苏城市化发展正面临新的发展机遇和挑战.处于快速发展的转型时期。通过对科学发展观在城市化发展中的定位思考,提出城市化发展过程中应注意的五个科学发展原则。在此战略原则的指导下.回顾总结了江苏省城市化进程中存在的粗放式速度增长与内涵式演变的错位、地域不平衡性与城乡差异性的加剧、城市体系的功能发挥失衡、缺乏区域协调与合作、人与生态环境的不和谐五个方面的问题.并以贯彻落实科学发展观思维为视角.从科学制定和实施城乡规划、构筑城市经营效率机制、把握沿江开发契机等措施层面,就全面推进江苏城市化科学发展作出了对策思考。  相似文献   
948.
Abstract:  The deep ocean is home to the largest ecosystems on our planet. This vast realm contains what may be the greatest number of animal species, the greatest biomass, and the greatest number of individual organisms in the living world. Humans have explored the deep ocean for about 150 years, and most of what is known is based on studies of the deep seafloor. In contrast, the water column above the deep seabed comprises more than 90% of the living space, yet less than 1% of this biome has been explored. The deep pelagic biota is the largest and least-known major faunal group on Earth despite its obvious importance at the global scale. Pelagic species represent an incomparable reservoir of biodiversity. Although we have yet to discover and describe the majority of these species, the threats to their continued existence are numerous and growing. Conserving deep pelagic biodiversity is a problem of global proportions that has never been addressed comprehensively. The potential effects of these threats include the extensive restructuring of entire ecosystems, changes in the geographical ranges of many species, large-scale elimination of taxa, and a decline in biodiversity at all scales. This review provides an initial framework of threat assessment for confronting the challenge of conserving deep pelagic biodiversity; and it outlines the need for baseline surveys and protected areas as preliminary policy goals.  相似文献   
949.
Floods are among the world's most devastating natural disasters, causing immense damage and accounting for a large number of deaths world-wide. Good flood management policies play an extremely important role in preventing floods. It is well known that China has more than 5000 years of experience in flood management policy beginning with the reign of DaYu and Gun. Although culturally related, Japanese flood management developed differently from that of China. Under rapid development of civil engineering technology, flood management was achieved primarily through the construction of dams, levees and other structures. These structures were never adequate to stop all floods, and recent climate change driven extreme events are ever more frequently overwhelming such infrastructure. It is important to take a historical perspective of Japanese and Chinese flood management in order to better manage increasingly frequent extreme events and climate change. We present insights taken from an historical overview of Japanese and Chinese flood management policies in order to guide future flood risk management policy.  相似文献   
950.
Biodiversity and Saving the Earth   总被引:1,自引:0,他引:1  
The challenges for reversing course in our stewardship of the earth's ecosystems has never been greater. Biodiversity is in decline on an unprecedented scale and it is tempting to use this as an indicator of the health of the earth's ecosystems. In fact it is one of a number of indicators that collectively provides information on trends in the condition of ecosystems. But the larger problem is the lack of integration between the social and natural sciences. Mainstream scientists continue to reject the notion that solving environmental problems requires an integration of values and processes. A conceptual model shows how these facets may be brought together. A holistic vision requires the integration of natural, social and health sciences. From this perspective the linkage between biodiversity, ecosystem resilience and management options is more clearly articulated.  相似文献   
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