The economic implications of recycling exhaustible natural resources: The case for crude oil

Regardless of whether the bulk of decision-making in an economy is done by a central unit or by decentralized smaller units, the government can act to propose guidelines to individual agents. This is of particular importance when the activities of the latter cause aggregative or social problems which are not directly acted upon by the smaller agents. The purpose of this paper is to set up a model by which a central authority can make choices in the presence of two pressing social problems, namely, a diminishing domestic supply of an exhaustible resource and the contamination of the environment through discharged waste materials.The model itself takes the form of an integer-linear programming problem which runs through discrete time to a finite horizon. Besides the traditional modes of “virgin” exploration and production and/or importation from abroad, society is also given the choice of recycling. Society will choose combinations of the above three to minimize the costs of satisfying fixed (projected) oil product demands in the future. The costs include those for increasing exploration for virgin refineries; for collection, refining and transportation for refineries and for the cost to society of discharges of waste-oil into the environment. The constraints include process flow restrictions, import quotas, capacity limits and discharge restrictions as well as fixed demands.An effort was made to keep the model as general as possible. Although no numerical solution is obtained in this paper, we feel that the policy implications of some presumed solution (possible through the use of a well-known algorithm for mixed variable problems) are worth examining. They revolve around the model itself, citing the potential attractiveness of recycling as the other two alternatives become increasingly expensive, and as development of alternatives to oil progresses at an alarmingly slow rate. Also mentioned are problems relating to the potential demands for recycled versus virgin oil products, balance-of-trade problems, and the mutability of social and economic institutions in the crisis of economic adjustment that much of the world is now facing.     

Interdependence of ecological risk and economic profit in the exploitation of renewable resources

A new stochastic optimal control approach is introduced which quantifies the risk of extinction of a population associated with its optimal exploitation. In addition the maximization of the profit can be performed subject to the constraint that the mentioned risk does not exceed a given limit. As a first example for this general method an exponentially growing population is investigated. The interdependence of the risk and the profit is discussed. This model reveals the possibility of reducing the risk considerably without a substantial decrease of profit.     

The contribution of environmental regulations to the slowdown in productivity growth

The radical slowdown in productivity growth since 1965 is often attributed to environmental regulations. Several studies, varying widely in method, have attempted to assess this contribution. Here, these analyses are reviewed and critiqued, and a summary appraisal of the likely contribution of environmental regulations to the observed decrease in productivity growth is offered.     

Defecation by Salpa thompsoni and its contribution to vertical flux in the Southern Ocean

Measurements of the defecation rate of Salpa thompsoni were made at several stations during two cruises west of the Antarctic Peninsula in 2004 and 2006. Rates were quantified in terms of number of pellets, pigment, carbon and nitrogen for a wide size range of both aggregate and solitary salps. Measured defecation rates were constant over several hours when salps were held at near-surface conditions from which they had been collected. The defecation rate per salp increased with both salp size and the ambient level of particulate organic matter (POM) in the upper water column. The weight-specific defecation rate ranged between 0.5 and 6% day⁻¹ of salp body carbon, depending on the concentration of available particulate matter in the water. Carbon defecation rates were applied to biomass estimates of S. thompsoni to calculate daily carbon defecation rates for the populations sampled during the two cruises. Dense salp populations of over 400 mg C m⁻² were calculated to produce about 20 mg C m⁻² day⁻¹, comparable to other major sources of vertical flux of organic material in the Southern Ocean. Measured sinking rates for salp fecal pellets indicated that the majority of this organic material could reach deep sediments within a few days, providing a fast and direct pathway for carbon to the deep ocean.     

Pastoralists' responses to variation of rangeland resources in time and space.

We explore the response of pastoralists to rangeland resource variation in time and space, focusing on regions where high variation makes it unlikely that an economically viable herd can be maintained on a single management unit. In such regions, the need to move stock to find forage in at least some years has led to the evolution of nomadism and transhumance, and reciprocal grazing agreements among the holders of common-property rangeland. The role of such informal institutions in buffering resource variation is well documented in some Asian and African rangelands, but in societies with formally established private-property regimes, where we focus, such institutions have received little attention. We examine agistment networks, which play an important role in buffering resource variation in modern-day Australia. Agistment is a commercial arrangement between pastoralists who have less forage than they believe they require and pastoralists who believe they have more. Agistment facilitates the movement of livestock via a network based largely on trust. We are concerned exclusively with the link between the characteristics of biophysical variation and human aspects of agistment networks, and we developed a model to test the hypothesis that such a link could exist. Our model builds on game theory literature, which explains cooperation between strangers based on the ability of players to learn whom they can trust. Our game is played on a highly stylized landscape that allows us to control and isolate the degree of spatial variation and spatial covariation. We found that agistment networks are more effective where spatial variation in resource availability is high, and generally more effective when spatial covariation is low. Policy design that seeks to work with existing social networks in rangelands has potential, but this potential varies depending on localized characteristics of the biophysical variability.     

红壤旱地湿沉降氮特征及其对马唐-冬萝卜连作系统氮素平衡的贡献

大气湿沉降作为农田生态系统养分的重要来源却一直没有得到足够的重视。文章通过常规农作条件,采用自动降雨收集器结合田间实验方法,重点研究了红壤旱地牧草马唐(Digitaria ischaemum)和蔬菜冬萝卜(Raphanus sativus)连作期间大气湿沉降氮素特征,估算了湿沉降向该生态系统输入的氮量,讨论了其对该生态系统氮素平衡的贡献。结果发现,该研究区域不同月份大气湿沉降T-N平均质量浓度为3.91mg·L-1,其中NH4 -N、NO3--N的分别为1.21、0.61mg·L-1;试验期间,湿沉降输入马唐-冬萝卜连作系统的T-N为34.34kg·hm-2,其中冬萝卜生长期最多,占67.88%,湿沉降T-N对该系统氮素输入、输出、盈余的贡献分别为12.97%、17.65%、48.90%。湿沉降T-N对马唐生态系统氮素输入、输出、盈余的贡献分别为6.45%、16.54%、10.57%;对冬萝卜生态系统氮素输入、输出的贡献分别为24.86%和18.23%。红壤旱地普遍具有"酸瘦黏板"的特点,氮素作为一种重要的生命物质和作物营养的必需元素,对作物产量和人民生活质量的提高具有重要的意义。研究结果表明,湿沉降对农田生态系统的影响不容忽视。     

The contribution of derelict mineral and industrial sites to the conservation of rare plants in the United Kingdom

The contribution of derelict industrial sites to the conservation of rare plants in the British Isles is reviewed. Many sites have acquired considerable biological interest and have been designated Sites of Special Scientific Interest or nature reserves. In most cases the development of wildlife interest has in the past been fortuitous rather than planned. There is, however, increasing evidence that the deliberate re-development of specific areas of derelict land for wildlife conservation is technical feasible. Whilst the forward planning of new mineral developments must continue to take account of existing wildlife values to minimise potential conflict and losses, nature conservation may, in certain circumstances, be considered as viable an endopoint as the more commonplace objectives of landscape rehabilitation. Further development of this policy could provide a means of compensating for the inevitable losses that will occur in the future, and greater attention must be paid to the potential of derelict industrial sites in this context.     

青檀天然群落土壤成分及其对青檀生长的影响

对湖北省三潭风景区青檀（Pteroceltis tatarinowii）天然群落土壤主要元素进行测定,并通过因子相关分析,探讨了土壤成分与青檀生长指标之间的相关性,研究结果可为青檀野生资源的保护和合理利用提供科学依据。结果表明,土壤水溶性Ca2＋、Mg2＋平均质量分数为3.598和0.176 g·kg-1,速效钾、全氮、有效磷的平均质量分数分别是133.324 mg·kg-1、4.413 g·kg-1和3.569 mg·kg-1,有机质平均质量分数为3.295%。土壤水溶性Ca2＋与青檀生长指标之间无显著相关关系;土壤可溶性Mg2＋与乔木、灌木的丛生植株数量呈显著正相关,当Mg2＋浓度处于0.191~0.221 g·kg-1之间时,青檀的丛生植株数量大;全氮与青檀乔木平均高度、平均胸径呈极显著正相关,与单生植株数量呈显著负相关;有效磷与乔木平均高度和胸径呈显著正相关;速效钾与乔木丛生植株数量及乔木总数量呈显著正相关;有机质灌木冠幅呈显著正相关。按土壤成分可将青檀群落聚成3类,3个聚类组的土壤水溶性Mg2＋、全氮（TN）、速效钾（TK）、有效磷（TP）、有机质以及青檀乔木植株总数量存在着显著差异。     

The natural food of the rabbitfish Siganus oramin and S. striolata

Specimens of juvenile and mature rabbitfish, Siganus oramin and S. striolata, were submitted to stomach analyses. Agarophytes of the genera Gracilaria, Hypnea and Laurencia proved to be the most preferred diet. Small invertebrates were ingested accidentally.     

岷江上游典型村落资源利用与影响动因分析

从耕地占有数量及利用效率、土地资源构成、村落农业生产技术以及村落布局4个方面,研究岷江上游4个典型村落农业资源利用变化特点,认为农业资源禀赋条件、科技进步程度、民族文化和历史因素、制度政策、市场因子以及生态环境状况是形成村落资源利用的基本动因。     

我国自然保护区有效管理现状及其分析

本文在对我国１０多个省（自治区）２ｏ多个自然保护区的实际调查和全国资料的统计分析基础上，从我国自然保护区的管理体制、管理机构建设、资源的保护与适度开发利用、科学研究与宣传教育等方面，全面分析了我国自然保护区有效管理的现状，总结了取得的成绩和存在的问题，并针对存在的主要问题，提出了相应的对策与建议。     

Gray Whales and the Value of Monitoring Data in Implementing the U.S. Endangered Species Act

Abstract: Many scientists lament the absence of data for endangered species and argue that more funds should be spent acquiring basic information about population trends. Using 19 years of abundance estimates for the eastern North Pacific gray whale ( Eschrichtius robustus ), we sampled subsets of the original survey data to identify the number of years of data required to remove the population from the U.S. Endangered Species Act's (ESA) list of endangered and threatened wildlife. For any given duration of monitoring, we selected all possible combinations of consecutive counts. To incorporate variability in growth rates, we extracted a maximum likelihood estimator of growth rate and confidence interval about that growth rate on the assumption that the population changes can be approximated by a simple diffusion process with drift. We then applied a new approach to determine ESA status for each subset of survey data and found that a quantitative decision to delist is unambiguously supported by 11 years of data but is precariously uncertain with fewer than 10 years of data. The data needed to produce an unequivocal decision to delist gray whales cost the National Marine Fisheries Service an estimated U.S. $660,000, a surprisingly modest expense given the fact that delisting can greatly simplify regulatory constraints. This example highlights the value of population monitoring in administering the ESA and provides a compelling example of the utility of such information in identifying both imperiled and recovered species. The economic value of such data is that they provide the foundation for delisting, which could ultimately save much more money than the collection of the data would ever cost.     

The nature of the photosynthate in natural phytoplankton populations in relation to light quality

The relative concentrations of a variety of organic compounds in phytoplankton from different depths of the photic zone of Saanich Inlet and Indian Arm, British Columbia, Canada, were determined. In surface phytoplankton the greatest proportion of ¹⁴C in newly-formed organic compounds was in the ethanol-soluble fraction irrespective of the light intensity. The proportion of the label in the insoluble fraction increased with depth. Within the ethanol-soluble fraction the relative importance of carbohydrates decreased and amino acids increased with depth. Experiments in Indian Arm indicated that these observed changes were in response to light quality rather than intensity. The percentage release of dissolved organic carbon as a percentage of total fixation decreased with depth and was directly related to the size of the ethanol-soluble fraction.     

The roles of nicotine and natural enemies in determining larval feeding site distributions of Manduca sexta L. and Manduca quinquemaculata (Haworth) on tobacco

Summary. Field observations indicated that hornworms select feeding sites non-randomly on tobacco. We tested the hypotheses that differences in feeding site locations of larvae of Manduca sexta L. and Manduca quinquemaculata (Haworth) (Lepidoptera: Sphingidae) on tobacco could be explained by differential nicotine concentrations within plants and leaves, species-specific responses to nicotine, or pressure exerted by natural enemies. Results showed that third-instar larvae of M. sexta fed more proximally and centrally on the leaf, whereas M. quinquemaculata fed more distally. Within-plant selection of leaves did not differ; both species selected leaves in the middle region of the plant. Nicotine concentrations in a high nicotine genotype, NC95, varied within each leaf, increasing 2—3 fold from the basal to apical portion of the leaf, and within each plant, increasing 7—10 fold from the first fully expanded leaf to the twelfth (lowest) leaf. In laboratory bioassays, both Manduca species responded to nicotine as a feeding deterrent. Electrophysiological studies demonstrated that gustatory organs of both species responded to nicotine at concentrations found in tobacco leaves and that M. quinquemaculata generally showed a less vigorous response to nicotine than M. sexta. Field mortality of M. sexta due to parasitism by Cotesia congregata (Say) and to parasitism and predation combined differed among feeding sites; predation alone did not. Results suggest that although nicotine concentration and species specific responses to nicotine play a role in determining feeding site locations, pressure exerted by natural enemies, especially parasitism by C. congregata, is more important. Received 22 February 2000; accepted 20 July 2001.     

The capacity of the filter-feeding bivalve Mya arenaria L. to affect water transport in sandy beds

Benthic filter feeding macrofauna organisms may be an important factor linking sediment and water column. Transport of water and concomitantly of suspended matter is directly related to the size of the benthic filter feeding population. This paper aims to determine the potential for water transport by the bivalve Mya arenaria along a coastal stretch of roughly 100 km length in the southern Baltic Sea. Quantification of population filtration rates specific to the area is based on distribution, abundance and biomass of M. arenaria and calculated according to previously published filtration rate–biomass relations. Calculated rates range up to >8 m³ m^–2 day^–1 (at 5–20 m water depth in sandy sediment) with the potential to locally process a volume of water equivalent to the water column within <1 day. Data from 1991–2002 at one site suggest that the area-specific potential population filtration rate remains remarkably constant in time despite changes in population structure of M. arenaria. The related impact on pore water exchange within the permeable sediment associated with the leakage of water from the gape of M. arenaria valves is discussed.Communicated by L. Hagerman, Helsingør     

Excretion of ammonia by zooplankton and its potential contribution to nitrogen requirements for primary production in the Catalan Sea (NW Mediterranean)

Excretion of ammonia by mesozooplankton (>200 m zooplankton) and its potential contribution to the nitrogen requirement for phytoplankton growth has been estimated for different hydrographical situations along a transect across the Catalan Sea (Northwestern Mediterranean). The nitrogen excreted as ammonia was estimated from mesozooplankton biomass and specific excretion rates. Nitrogen requirements of phytoplankton were estimated by means of carbon fixation rates and C:N ratios of <200 m particulate organic matter. Minimum C:N ratios and maximum primary production, zooplankton biomass, phytoplankton nitrogen requirements, and nitrogen excretion of zooplankton occurred near the Catalan density front. On average, the nitrogen regenerated by the mesozooplankton accounted for 43% of the nitrogen requirements of the phytoplankton. The specific excretion rates of ammonia and the percentage of phytoplanktonnitrogen requirements supplied by excreted nitrogen were higher at coastal stations. In some coastal and frontal stations, the ammonia excreted exceeded the phytoplanktonnitrogen demand. Bacteria competing for nutrient supply and the possible uncoupling between rate processes and standing stocks of phyto- and zooplankton could explain the apparent excess of regenerated ammonia.     

不同活性物种对光催化降解水中邻苯二甲酸二甲酯动力学的贡献研究

采用光催化氧化技术对邻苯二甲酸二甲酯（DMP）进行降解研究,并在基础上考察了催化剂量,溶液pH和溶液初始浓度对降解速率的影响。且采用Langmuir-Hinshelwood动力学模型来描述DMP的光催化降解,研究表明DMP的光催化降解符合假一级动力学。系统研究了光催化降解DMP过程中不同活性物种对光催化反应速率的贡献,实验结果表明：在TiO2光催化降解DMP的过程中,？OH为主要的活性物种,其对DMP的降解速率贡献高于94%,而其它活性物种（ecb-,hvb＋,O2？-和H2O2）对光催化贡献较小。     

美国杏李园主要害虫与天敌类群间相关性分析

应用典范相关分析方法研究了美国杏李园丰要害虫与天敌间的相互关系,在未受干扰的自生园中.害虫亚系统与天敌亚系统间第一典范相关系数达到显著水平,天敌亚系统中瓢虫类、草蛉类与主要害虫蚜虫类,螨类的数量变动规律一致.而蜘蛛类与主要害虫的数最关系不密切,化防园内主要害虫与天敌间的典范相关系数均未达显著永平,这表明未受干扰的自生园和生防园内,害虫与天敌亚系统间存在着有效的数量反馈机制,天敌对害虫具有一定的自然抑制作用,而化防园内,害虫与天敌间的数量反馈机制因农药干扰而失调,生态平衡受破坏.自生园和生防园害虫与天敌主要类群间具正相关关系.害虫亚系统中,蚜虫类贡献最大,其次为山楂叶螨和李小食心虫:天敌亚系统中蜘蛛和瓢虫贡献最大,其次为瓢虫类和草蛉类,草蛉类贡献最小.说明蜘蛛类、瓢虫类与主要害虫的数量变动规律一致.而草蛉类与美国杏李园主要害虫的数量关系不密切.     

The relative contribution of dinoflagellate photosynthesis and stored lipids to the survivorship of symbiotic larvae of the reef-building corals

The long-distance dispersal of larvae provides important linkages between populations of reef-building corals and is a critical part of coral biology. Some coral planulae have symbiotic dinoflagellates (Symbiodinium spp.) that probably provide energy in addition to the lipids provisioned within the egg. However, our understanding of the influence of symbionts on the energy metabolism and survivorship of planulae remains limited. This study examines the relative roles of symbiotic dinoflagellate photosynthesis and stored lipid content in the survivorship of the developing stages of the corals Pocillopora damicornis and Montipora digitata. We found that survivorship decreased under dark conditions (i.e. no photosynthetic activity) for P. damicornis and M. digitata at 31 and 22 days after release/spawning, respectively. The lipid content of P. damicornis and M. digitata planulae showed a significant decrease, at a higher rate, under dark conditions, when compared with light conditions. When converted to energy equivalents, the available energy provided by the depletion of lipids could account for 41.9 and 84.7% of larval metabolism for P. damicornis (by day 31) and 38.4 and 90.1% for M. digitata (by day 21) under light and dark conditions, respectively. This finding indicates that not all energy requirements of the larvae are met by lipids: energy is also sourced from the photosynthetic activities of the symbiotic dinoflagellates within these larvae, especially under light conditions. In addition, the amounts of three main lipid classes (wax esters, triglycerides, and phospholipids) decreased throughout the experiment in the planulae of both species, with the wax ester content decreasing more rapidly under dark conditions than under light conditions. The observations that the planulae of both species derive considerable amounts of energy from wax esters, and that symbiotic dinoflagellates enable larvae to use their stores at lower rates, suggested that symbiotic dinoflagellates have the potential to extend larval life under light conditions.