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51.
Will Limits of the Earth's Resources Control Human Numbers? 总被引:1,自引:1,他引:0
David Pimentel O. Bailey P. Kim E. Mullaney J. Calabrese L. Walman F. Nelson X. Yao 《Environment, Development and Sustainability》1999,1(1):19-39
The current world population is 6 billion people. Even if we adopted a worldwide policy resulting in only 2.1 children born per couple, more than 60 years would pass before the world population stabilized at approximately 12 billion. The reason stabilization would take more than 60 years is the population momentum – the young age distribution – of the world population. Natural resources are already severely limited, and there is emerging evidence that natural forces already starting to control human population numbers through malnutrition and other severe diseases. At present, more than 3 billion people worldwide are malnourished; grain production per capita has been declining since 1983; irrigation per capita has declined 12% during the past decade; cropland per capita has declined 20% during the past decade; fish production per capita has declined 7% during the past decade; per capita fertilizer supplies essential for food production have declined 23% during the past decade; loss of food to pests has not decreased below 50% since 1990; and pollution of water, air, and land has increased, resulting in a rapid increase in the number of humans suffering from serious, pollution-related diseases. Clearly, human numbers cannot continue to increase. 相似文献
52.
Graduated licensing has been implemented in many U.S. states to reduce teenage driver crash involvement. The goal is to introduce teenagers gradually to driving before allowing full, unrestricted licensure. Tennessee, one of the states that introduced graduated licensing, implemented a program to influence both driving by teenagers during the learner stage and restrictions imposed by parents after licensure. In addition to a standard welcome letter, booklets and reminder cards were mailed to parents of teenagers who had just obtained their learner's permits. The booklets and cards were designed to assist parents in becoming more actively involved in their children's driving experiences. The effects of three different approaches (welcome letter only, letter plus booklet, and letter plus booklet plus reminder cards) on parental involvement, teenage crashes, and teenage citations were assessed based on telephone interviews with parents. Although the parents said the booklets and reminder cards were helpful and should continue to be sent to other parents, there were no discernible effects on teenage practice driving and reported parental involvement during the learner stage. Nor was there any measurable influence on restrictions imposed by parents after licensure. It is unknown whether the standard welcome letter affected parental involvement, but overall supervised driving exceeded the state requirements by a substantial margin. 相似文献
53.
Abstractions of surface and groundwater for irrigation in Scotland are currently subject to control in only two small catchments. Under the terms of the EU Water Framework Directive, it will be necessary to introduce new legislation to control abstractions elsewhere. To help in the development of appropriate policy for Scotland a study has been carried out to examine the significance of irrigation and the effectiveness of different types of control strategies in terms of the economics of potato cropping and stream hydrology in Scotland. This paper presents the findings of the hydrological study and highlights some of the spatial and temporal issues that need to be considered in the selection of control mechanisms, if they are to be successful in achieving objectives for environmental improvement.The study was focussed on two catchments in the east of Scotland, the Tyne and West Peffer. The effectiveness of several different abstraction control strategies was examined to see how stream flows in the catchment would be modified by their implementation. The results of the study demonstrated that the West Peffer catchment in particular is significantly affected by irrigation abstractions. Control mechanisms based on allowable monthly abstraction volumes and flow-based abstraction bans would be of considerable help in restoring stream flows to their natural levels, but would modify the hydrological regime in slightly different ways. A spatial analysis of stream flows demonstrated that implementation of controls based on a single monitoring point may be ineffective at maintaining acceptable levels of flow throughout the catchment and that this may require a tighter control at the monitoring point. 相似文献
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55.
Donald R. Field Neil H. Cheek 《Journal of the American Water Resources Association》1974,10(6):1218-1227
ABSTRACT: Participation in water-based recreation activities does not arise in random fashion nor simply as a result of having a water resource immediately available. Neither do individuals and groups engage in the same activities or a specific activity in the same way. The purpose of the present paper is to describe an alternative framework whereby differences among recreation users can be identified. Prior to this time, research directed toward understanding participation patterns at a recreational site have emphasized the activities while ignoring the human behavior factors which determine how participation arises. People consider recreation sites to be leisure settings in which the definition of such places has a broader socio-cultural meaning than that the site was designed. These definitions are reflected within the context of the social group and can be observed in the subsequent orientation to leisure and play. When activities are considered in the context of a human group, differences in participation patterns can be discovered. 相似文献
56.
Rhys Worrall David Neil David Brereton David Mulligan 《Journal of Cleaner Production》2009,17(16):1426-1434
Sustainable development practices have become an integral part of most major mining companies’ business activities. However, the history of mining and the negative impacts it has had on the natural and social environment mean future mining activities, rightly or wrongly, will be judged against the legacies of the past and current poor performers. Legacy mine land, defined here as land which has been mined and is now being used for another purpose, or is orphaned, abandoned or derelict and in need of remedial work, is one management challenge that will be judged in the context of sustainable development. Globally, millions of such sites exist. Having criteria against which to measure progress toward or away from sustainable development goals is a key to delivering results. The aim of this research was to develop a sustainability criteria and indicators framework to suit the particular needs of legacy mine land. The resulting framework consists of 14 criteria and 72 indicators. 相似文献
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58.
Abstract: The endangered Hawaiian monk seal breeds at six locations in the northwestern Hawaiian Islands. To determine whether significant genetic differentiation exists among these sites, we used microsatellite loci to examine the monk seal population structure at the five largest breeding colonies. Of 27 loci isolated from other seal species, only 3 were polymorphic in an initial screening of one individual from each breeding site. Only two alleles were found at each of these 3 loci in samples of 46–108 individuals. This extremely low variation is consistent with other measures of genetic variability in this species and is probably the result of a recent severe population bottleneck, combined with a long-term history of small population sizes. Although the smallest monk seal subpopulation in this study ( Kure Atoll) showed some evidence of heterozygote deficit, possibly indicative of inbreeding, the next smallest ( Pearl and Hermes Reef) had an apparent excess of heterozygous individuals. Genetic differentiation was detected between the two subpopulations at extreme ends of the range ( Kure and French Frigate Shoals). This trend was significant only at the microsatellite locus for which we had the largest sample size ( Hg6.3: R ST = 0.206, p = 0.002; allelic goodness of fit G h = 15.412, p < 0.005). French Frigate Shoals is the source population for translocated animals that have been released primarily at Kure Atoll. Differentiation between these sites consisted of allele frequency differences (with the same allele predominant in each location at all three loci), rather than the preservation of alternative alleles. Although the translocations have had positive demographic effects, we recommend continued genetic monitoring of both the source and recipient populations because translocated individuals are now entering the breeding population. 相似文献
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60.
The proboscis extension reflex (PER) is widely used in a classical conditioning (Pavlovian) context to evaluate learning and memory of a variety of insect species. The literature is particularly prodigious for honeybees (Apis mellifera) with more than a thousand publications. Imagination appears to be the only limit to the types of challenges to which researchers subject honeybees, including all the sensory modalities and a broad diversity of environmental treatments. Accordingly, some remarkable insights have been achieved using PER. However, there are several challenges to evaluating the PER literature that warrant a careful and thorough review. We assess here variation in methods that makes interpretation of studies, even those researching the same question, tenuous. We suggest that the numerous variables that might influence experimental outcomes from PER be thoroughly detailed by researchers. Moreover, the influence of individual variables on results needs to carefully evaluated, as well as among two or more variables. Our intent is to encourage investigation of the influence of numerous variables on PER results. 相似文献