Renewable Resources in an Overlapping Generations Economy Without Capital

We incorporate a renewable resource into an overlapping generations model without capital and with quasi-linear preferences. Besides being an input for production the resource serves as a store of value. We characterize the dynamics, efficiency, and stability of the steady-state equilibria. The stability properties are sensitive to the type of resource growth. For constant growth there is only one steady-state equilibrium which is stable and efficient. In the general case of the concave growth function, there are usually at least two steady-state equilibria, one of which is stable and the other one unstable. The unstable steady state is efficient, but the stable one may or may not be. We study the robustness of our results by assuming a logarithmic utility function. We show that for the Cobb–Douglas production function the steady state is unique and stable regardless of whether the equilibrium is efficient or inefficient. Our analytical results are illustrated by numerical calculations.     

The Impact of Landsat Satellite Monitoring on Conservation Biology

Landsat 7s recent malfunctioning will result in significant gaps in long-term satellite monitoring of Earth, affecting not only the research of the Earth science community but also conservation users of these data. To determine whether or how important Landsat monitoring is for conservation and natural resource management, we reviewed the Landsat programs history with special emphasis on the development of user groups. We also conducted a bibliographic search to determine the extent to which conservation research has been based on Landsat data. Conservation biologists were not an early user group of Landsat data because a) biologists lacked technical capacity – computers and software – to analyze these data; b) Landsats 1980s commercialization rendered images too costly for biologists budgets; and c) the broad-scale disciplines of conservation biology and landscape ecology did not develop until the mid-to-late 1980s. All these conditions had changed by the 1990s and Landsat imagery became an important tool for conservation biology. Satellite monitoring and Landsat continuity are mandated by the Land Remote Sensing Act of 1992. This legislation leaves open commercial options. However, past experiments with commercial operations were neither viable nor economical, and severely reduced the quality of monitoring, archiving and data access for academia and the public. Future satellite monitoring programs are essential for conservation and natural resource management, must provide continuity with Landsat, and should be government operated.     

我国淡水水域光合产物的气候生产力探讨

根据太阳辐射在水体中的有效分布、生长季水温和浮游植物光合生态特性等因子,模拟计算了我国大陆东部淡水水域的光合生产力、气候生产力及其季节变化的地理规律。从中得知,这些水域初级产物的年气候生产力主要呈纬向分布,由南向北递减,各地范围在 1.6-24.4gC/m²·a之间,长江以南是>15.0gC/m²·a的高值区,长城以北和四川盆地为<10.0gC/m²·a的低值区,因此,在气候生产力高值区有可能充分利用气候资源优势,开发低成本的自然淡水水域渔业;而在低生产力区,受自然资源的局限其自然捕鱼量需适量控制,因地制宜。     

不可再生资源利用率度量指标研究

通过分析指出不可再生资源利用率是度量可持续发展的一个重要尺度。从产值与不可再生资源消耗相比较的角度出发 ,设置了不可再生资源利用率的度量指标 :单位工业增加值不可再生资源消耗 ,并以中国为例 ,分别以重量与能值为尺度 ,计算以上所设置指标的指标值 ,并对计算结果进行分析与思考。     

微藻对水网藻在水体修复中的胁迫作用研究

通过单独与混合培养实验,结果显示在适宜营养水平下,水网藻对氮、磷有较强的富集吸收能力;而来自微藻生长竞争的压力会促使水网藻对营养物的生态幅变窄,满足其最佳生长所需要的PO43-P从0.085mg/L降低为0.024mg/L;并且其富集磷的能力也大为降低。在利用水网藻进行富营养化水体修复或净化水质时,这种生物之间的抑制现象必须引起重视。     

Fisheries management: integrating societal preference, decision analysis, and ecological risk assessment

Fisheries management is the practice of analyzing and selecting options to maintain or alter the structure, dynamics, and interaction of habitat, aquatic biota, and man to achieve human goals and objectives. The theory of fisheries management is: managers or decision makers attempt to maximize renewable `output' from an aquatic resource by choosing from among a set of decision options and applying a set of actions that generate an array of outputs. Outputs may be defined as a tangible catch, a fishing experience, an existence value, or anything else produced or supported by renewable aquatic resources. Overall output is always a mix of tangible and intangible elements. However defined, management goals and objectives are essential components of fisheries management or any other field of renewable natural resource management. Reaching consensus on management goals and objectives has never been a simple task. Beyond the broad and often conflicting goals of an agency, managers must decide who should set specific management objectives — agency personnel, the public, or a combination of the two. Historically, rhetoric aside, fisheries managers in North America nearly always have consulted with professionals in governmental roles to set management objectives. In a strongly pluralistic society, this often resulted in protracted political and legal conflict. Increasingly, there are calls for use of risk assessment to help solve such ecological policy and management problems commonly encountered in fisheries management. The basic concepts of ecological risk assessment may be simple, but the jargon and details are not. Risk assessment (and similar analytical tools) is a concept that has evoked strong reactions whenever it has been used. In spite of the difficulties of defining problems and setting management objectives for complex ecological policy questions, use of risk assessment to help solve ecological problems is widely supported. Ecological risk assessment will be most useful (and objective) in political deliberations when the policy debate revolves around largely technical concerns. To the extent that risk assessment forces policy debate and disagreement toward fundamental differences rather than superficial ones, it will be useful in decision making.     

区域土地资源承载能力研究模式雏议——以甘肃省定西县为例

本文从土地现实生产力分析和作物潜在生产力估算入手,借助IBM-PC计算机,通过土地资源生产力评价的 MFICA 模式和土地资源优化利用模型的建立,初步框算了定西县1990年、2000年,2025年以及2050年之后的区域农业生产力及其土地资源承载力,进尔阐释了该县土地资源承载力的演变及其土地-粮食-人口关系的可能发展趋势。为区域土地资源承载力研究提供了一条切实可行的途径。     

浅谈内蒙古草原生态环境现状及其保护对策

本文针对当前内蒙古草原生态环境现状以及草原资源利用所面临的问题，从利用制度、管理措施等多方面提出了加强草原保护和合理利用的相应对策。     

浅析元宝山露天矿疏干排水存在的问题

通过对元宝山露天矿疏干水现存问题的探讨 ,对问题成因进行分析 ,找出解决问题的的具体办法 ,为露天疏干水建设提供模型     

浅谈荆马河污水资源化生态工程

遵循可持续发展的原则，针对经济欠发达地区的水环境污染现状，提出了兴建产业化的污水处理生态工程，科学地发展污灌，既有效地改善了京杭运河（徐州段）的水环境质量，又使徐州市城市污水得以资源化利用，对促进环境与社会经济协调发展具有积极意义。