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Abstract: Urban planners acquire open space to protect natural areas and provide public access to recreation opportunities. Because of limited budgets and dynamic land markets, acquisitions take place sequentially depending on available funds and sites. To address these planning features, we formulated a two-period site selection model with two objectives: maximize the expected number of species represented in protected sites and maximize the expected number of people with access to protected sites. These objectives were both maximized subject to an upper bound on area protected over two periods. The trade-off between species representation and public access was generated by the weighting method of multiobjective programming. Uncertainty was represented with a set of probabilistic scenarios of site availability in a linear-integer formulation. We used data for 27 rare species in 31 candidate sites in western Lake County, near the city of Chicago, to illustrate the model. Each trade-off curve had a concave shape in which species representation dropped at an increasing rate as public accessibility increased, with the trade-off being smaller at higher levels of the area budget. Several sites were included in optimal solutions regardless of objective function weights, and these core sites had high species richness and public access per unit area. The area protected in period one depended on current site availability and on the probabilities of sites being undeveloped and available in the second period. Although the numerical results are specific for our study, the methodology is general and applicable elsewhere. 相似文献
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China has embarked on major economic and social changes to revitalize the Chinese economy, increase labor productivity, and improve the material standard of living of the Chinese people. This paper assumes that China will achieve its goal of a per capita income of US$800 in 2000, open-door policies will be maintained, and nonfuel mineral commodity consumption will increase as GDP per capita increases. Projections are made of production, trade and consumption of 14 nonfuel minerals for the period 1985–2005. China is projected to increase its net imports to these 14 minerals from about US$5000 million in 1985 to about US$12000 million in constant dollars in 2005. China's investment climate will become more favorable for those multinational companies that bring with them clear comparative advantages in minerals exploration, mining and processing technologies and marketing, and are prepared to develop in-depth Chinese expertise. 相似文献
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Conserving Slow-Growing, Long-Lived Tree Species: Input from the Demography of a Rare Understory Conifer, Taxus floridana 总被引:1,自引:0,他引:1
Abstract: Although land preservation and promotion of successful regeneration are important conservation actions, their ability to increase population growth rates of slow-growing, long-lived trees is limited. We investigated the demography of Taxus floridana Nutt., a rare understory conifer, in three populations in different ravine forests spanning its entire geographic range along the Apalachicola River Bluffs in northern Florida (U.S.A.). We examined spatial and temporal patterns in demographic parameters and projected population growth rates by using four years of data on the recruitment and survival of seedlings and established stems, and on diameter growth from cross-sections of dead stems. All populations experienced a roughly 10-fold increase in seedling recruitment in 1996 compared with other years. The fates of seedlings and stems between 8 and 16 mm differed among populations. The fates of stems in two other size classes (the 2- to 4-mm class and the 4- to 8-mm class) differed among both populations and years. Individual stems in all populations exhibited similarly slow growth rates. Stochastic matrix models projected declines in all populations. Stochastic matrix analysis revealed the high elasticity of a measure of stochastic population growth rate to perturbations in the stasis of large reproductive stems for all populations. Additional analyses also indicated that occasional episodes of high recruitment do not greatly affect population growth rates. Conservation efforts directed at long-lived, slow-growing rare plants like Taxus floridana should both protect established reproductive individuals and further enhance survival of individuals in other life-history stages, such as juveniles, that often do not appear to contribute greatly to population growth rates. 相似文献
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Taxus brevifolia , a subcanopy tree or shrub in forests of the Pacific Northwest, has been harvested intensively in recent years. With management concerns as an impetus, we examined the distribution and population dynamics of Taxus based on data from the mountains of western Oregon and Washington. Surveys of natural forests, long-term studies of forest recovery following logging, and census data on marked trees in forest stands support the hypothesis that Taxus is a widespread but predominantly late-successional species. Sensitive to fire and slow to recover from disturbance on many sites, Taxus attains maximal basal area and adult stem density in old forests. Colonization of Taxus is often slow in potentially suitable habitats. Conservation of Taxus at the landscape level may require large, unmanaged reserves and maintenance of patches of old forest within managed forests. Long rotations (centuries) between harvest events will enhance the long-term viability of the species. Practices designed to accelerate the development of old-growth forest structure will not benefit Taxus and other species requiring long disturbance-free intervals for recovery. 相似文献
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ASTRID J. SCHOLZ CHARLES STEINBACK SARAH A. KRUSE MIKE MERTENS HOWARD SILVERMAN 《Conservation biology》2011,25(3):485-492
Abstract: Social, economic, and ecological criteria contribute to the successful design, implementation, and management of marine protected areas (MPAs). In the context of California's Marine Life Protection Act Initiative, we developed a set of methods for collecting, compiling, and analyzing data about the spatial extent and relative economic importance of commercial and recreational fishing. We interviewed 174 commercial fishers who represented the major fisheries in the initiative's north‐central coast region, which extends from Point Arena south to Pigeon Point. These fishers provided data that we used to map the extent of each of the fishing grounds, to weight the relative importance of areas within the grounds, to characterize the operating costs of each fishery, and to analyze the potential economic losses associated with proposed marine protected areas. A regional stakeholder group used the maps and impact analyses in conjunction with other data sets to iteratively identify economic and ecological trade‐offs in designations of different areas as MPAs at regional, port, and fishery extents. Their final proposed MPA network designated 20% of state waters as MPAs. Potential net economic loss ranged from 1.7% to 14.2% in the first round of network design and totaled 6.3% in the final round of design. This process is a case study in the application of spatial analysis to validate and integrate local stakeholder knowledge in marine planning. 相似文献
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NILS BUNNEFELD CHARLES T. T. EDWARDS ANAGAW ATICKEM FETENE HAILU E. J. MILNER‐GULLAND 《Conservation biology》2013,27(6):1344-1354
Conservation scientists are increasingly focusing on the drivers of human behavior and on the implications of various sources of uncertainty for management decision making. Trophy hunting has been suggested as a conservation tool because it gives economic value to wildlife, but recent examples show that overharvesting is a substantial problem and that data limitations are rife. We use a case study of trophy hunting of an endangered antelope, the mountain nyala (Tragelaphus buxtoni), to explore how uncertainties generated by population monitoring and poaching interact with decision making by 2 key stakeholders: the safari companies and the government. We built a management strategy evaluation model that encompasses the population dynamics of mountain nyala, a monitoring model, and a company decision making model. We investigated scenarios of investment into antipoaching and monitoring by governments and safari companies. Harvest strategy was robust to the uncertainty in the population estimates obtained from monitoring, but poaching had a much stronger effect on quota and sustainability. Hence, reducing poaching is in the interests of companies wishing to increase the profitability of their enterprises, for example by engaging community members as game scouts. There is a threshold level of uncertainty in the population estimates beyond which the year‐to‐year variation in the trophy quota prevented planning by the safari companies. This suggests a role for government in ensuring that a baseline level of population monitoring is carried out such that this level is not exceeded. Our results illustrate the importance of considering the incentives of multiple stakeholders when designing frameworks for resource use and when designing management frameworks to address the particular sources of uncertainty that affect system sustainability most heavily. Incentivando el Monitoreo y el Cumplimiento en la Caza de Trofeos 相似文献
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Workplace romances and sexual harassment are pervasive in today's organizations. However, despite the fact that these two phenomena share a social-sexual component, they have primarily been treated as unrelated organizational issues. We advance an affective link between workplace romances and sexual harassment. Based on this theoretical connection, we discuss conditions under which workplace romances may result in sexual harassment. Finally, we address managerial implications of the romance–harassment link. © 1997 John Wiley & Sons, Ltd. 相似文献
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The paper attempts to examine the coal challenge for the developing countries by examining the potential of coal as an energy source in developing countries by identifying the factors which constrain its expanded use and by discussing the steps needed to develop this potential. The coal experience of several developing countries is examined to create a sense of realism and an agenda for change is presented.
Cet article passe en revue les possibilités offertes par le charbon aux pays en développement. Il considère le potentiel que représente le charbon en tant que source d'énergie pour ces pays. Il prend en compte les facteurs qui empêchent de développer son utilisation en étudie les mesures à prendre pour mettre ce potentiel en valeur. Pour illustrer ce point de vuc. il examine l'expérience de plusieurs pays en développement dans ce domaine. Pour conclure, l'article présente un calendrier des changements possibles.
El artículo examina el potencial del carbón como fuente de energía en los países en desarrollo identifica los factores que restringen su uso más generalizado. Se examina la experiencia concreta de varios paises en desarrollo y se proponen medidas para ampliar la contribución del carbón en el suministro de energía. 相似文献
Cet article passe en revue les possibilités offertes par le charbon aux pays en développement. Il considère le potentiel que représente le charbon en tant que source d'énergie pour ces pays. Il prend en compte les facteurs qui empêchent de développer son utilisation en étudie les mesures à prendre pour mettre ce potentiel en valeur. Pour illustrer ce point de vuc. il examine l'expérience de plusieurs pays en développement dans ce domaine. Pour conclure, l'article présente un calendrier des changements possibles.
El artículo examina el potencial del carbón como fuente de energía en los países en desarrollo identifica los factores que restringen su uso más generalizado. Se examina la experiencia concreta de varios paises en desarrollo y se proponen medidas para ampliar la contribución del carbón en el suministro de energía. 相似文献