Relating environmental modeling to policy issues and decisions

This paper describes a linear program-based computer model which has been developed to identify the most effective spending patterns for environmental cleanup based on public preferences and spending limitations. The inputs to the model include the costs of removing each residual studied from its various sources. The objective function is the total “value of removal”. The factor added for each residual consists of a value for the residual multiplied by the quantity or fraction removed.Results of the analysis relate to and support current and projected policy decisions by the U.S. Environmental Protection Agency (EPA) for air and water programs. In addition, the results of the analysis suggest that EPA undertake a redirection of the Nation's resources among residual control programs.     

Measuring values for environmental resources under uncertainty

The relationship between conventional Hicksian measures of the benefits from changes in environmental amenities under certainty, and corresponding measures of valuation when the conditions of access to an uncertain environmental resource are changed, is considered. The analysis utilizes a contingent commodity framework with the assumption of state-dependent preferences. The findings suggest that the valuation of these changes will depend upon the availability of fair markets for diversifying risk. Moreover, conventional measures of compensating or equivalent surplus will not necessarily bound the individual's valuation of a change in access to an uncertain environmental resource.     

Control theory applied to natural and environmental resources an exposition

Four control theory models of natural and environmental resource use, drawn from the existing literature, are developed in a manner to emphasize their technical and decentralized interpretive similarity. Renewable, nonrenewable, and amenity resource use are treated as closely related problems of optimal (biological, earth material, ecological, or environmental) capital allocation over time. Thus nonrenewable resources, and the problem of exhaustion, are just limiting (zero growth) cases of renewable resources, and the problem of species extinction. Just as exhaustion can be optimal, extinction can be optimal. Waste recycling is treated as part of the problem of optimal regeneration of “sclean” environmental capital; wilderness use as a problem of managing the regeneration of ecological capital.     

Modelling plant resource allocation and growth partitioning in response to environmental heterogeneity

Plant morphological adjustment in response to spatial resource heterogeneity is an important factor that determines the outcomes of plant–plant and plant–environment interactions. In this study, a dynamic model of resource allocation and growth partitioning at the whole-plant level is presented. The aim is to suggest a mechanism by which plants are capable of modifying their resource allocation to favour the growth of their growing parts sited in resource-rich patches. In this model, an individual plant is treated as a population of relatively independent subunits competing for internal resources. The growth decision of individual shoot and root subunits depends on their local endogenous nutrient status. The allocation of nutrients to different shoot parts and root parts is determined by the structure of the vascular networks. No specific partitioning functions and driving coefficients are introduced in the model to coordinate resource allocation and growth partitioning at the whole-plant level. Vascular tissues acquire resources from the nutrient flow passing through them to grow and maintain their activities. The simulation results show that, based on simple rules of nutrient supply, transport and utilization, plants are able to integrate activities at the whole-plant level to allocate proportionally more growth to their growing parts in the most favourable positions.     

Flexibility,learning, and irreversibility in environmental decisions: A bayesian approach

The Bayes decision is characterized and studied for a two-period decision problem involving a proposed resource development project. It is assumed that development is irreversible and that expectations about benefits and costs during the second period vary with experiences resulting from the first-period action. The amount and types of learning achieved depend upon the particular action taken during the first period. Flexible sequential decision procedures are compared with fixed once-and-for-all decisions. It is shown that under this specification, optimal development decisions are not necessarily more conservative when a sequential procedure is used. The possibility of reneging on a fixed decision is formally specified and studied.     

Uncertainty analysis on aquatic environmental impacts of urban land use change

Uncertainties hamper the implementation of strategic environmental assessment (SEA). In order to quantitatively characterize the uncertainties of environmental impacts, this paper develops an integrated methodology through uncertainty analysis on land use change, which combines the scenario analysis approach, stochastic simulation technique, and statistics. Dalian city in China was taken as a case study in the present work. The results predict that the Fuzhou River poses the highest environmental pollution risk with a probability of 89.63% for COD in 2020. Furthermore, the Biliu River, Fuzhou River, Zhuang River, and Dasha River have 100% probabilities for NH₃-N. NH₃-N is a more critical pollutant than COD for all rivers. For COD, industry is the critical pollution source for all rivers except the Zhuang River. For NH₃-N, agriculture is the critical pollution source for the Biliu River, Yingna River, and Dasha River, sewage for the Fuzhou River and Zhuang River, and industry for the Dengsha River. This methodology can provide useful information, such as environmental risk, environmental pressure, and extremely environmental impact, especially under considerations of uncertainties. It can also help to ascertain the significance of each pollution source and its priority for control in urban planning.     

Determine the most influencing stressors and the most susceptible resources for environmental integrated assessment

The paper presents a method to determine the most influencing stressors and the most susceptible resources for complex assessment problems involving multiple stressors impacting multiple resources over a region. The method is based on the concept of limiting priorities in a square matrix which capture the transmission of influence along all paths between stressors and resources in the matrix. The proposed method allows the relationship between stressors and resources to be looked at in both univariate and multivariate fashion, taking into account the interactions among the variables. Hypothetical and case study examples are given for illustration purpose. It shows that the proposed method is suitable for the determination of the most important stressors and the most susceptible resources, a common (but often uneasy) task in integrated environmental assessment.     

苔藓植物资源保护利用中的生态环境效应研究进展

苔藓植物资源丰富、种类繁多、分布广泛,是一类以孢子繁殖,由水生向陆生过渡的高等植物。苔藓植物的结构相对简单,对环境变化的反应较为敏感,被广泛应用为环境污染的指示植物。苔藓植物生长与所处的环境有关,而它的生长对土壤结皮形成、水土保持、生态小环境改善等方面又发挥着重要的促进作用。综述了苔藓植物的资源分布、苔藓植物对环境污染的响应、苔藓植物的生态效应等方面的研究进展,但是目前的研究领域及其研究角度还存在着各自的不足。随着经济建设快速发展,世界各地大量的矿山开采、水电开发等工程建设对土地、自然环境的破坏日益严重,非农业建设以及农产品需求不断增加造成了农田的生态结构与功能发生着不断变化。针对各地经济社会发展以及城乡建设现状,积极开展工程建设领域以及农田生态系统苔藓植物的生态环境效应研究是今后值得十分重视的研究方向。     

苔藓植物资源保护利用中的生态环境效应研究进展

苔藓植物资源丰富、种类繁多、分布广泛,是一类以孢子繁殖,由水生向陆生过渡的高等植物。苔藓植物的结构相对简单,对环境变化的反应较为敏感,被广泛应用为环境污染的指示植物。苔藓植物生长与所处的环境有关,而它的生长对土壤结皮形成、水土保持、生态小环境改善等方面又发挥着重要的促进作用。综述了苔藓植物的资源分布、苔藓植物对环境污染的响应、苔藓植物的生态效应等方面的研究进展,但是目前的研究领域及其研究角度还存在着各自的不足。随着经济建设快速发展,世界各地大量的矿山开采、水电开发等工程建设对土地、自然环境的破坏日益严重,非农业建设以及农产品需求不断增加造成了农田的生态结构与功能发生着不断变化。针对各地经济社会发展以及城乡建设现状,积极开展工程建设领域以及农田生态系统苔藓植物的生态环境效应研究是今后值得十分重视的研究方向。     

A goal interval programming model for resource allocation in a marine environmental protection program

A multidimensional “goal programming” model is developed to aid resource allocation decisions in the U. S. Coast Guard's Marine Environmental Protection (MEP) program. It is then extended to a model of “goal interval programming” (GIP ) type where exact values for the indicated goals, as in ordinary goal programming, are replaced by ranges. Deviations outside these ranges are also accommodated by piecewise linear functions with slopes that vary with distance from the goal intervals. Uses and generalizations are discussed in the context of applications to allocating manhours and planning the activities of the Coast Guard's MEP program.     

On costs and decisions in population management

Many populations have a negative impact on their habitat, or upon other species in the environment, if their numbers become too large. For this reason they are often managed using some form of control. The objective is to keep numbers at a sustainable level, while ensuring survival of the population. Here we present models that allow population management programs to be assessed. Two common control regimes will be considered: reduction and suppression. Under the suppression regime the population is maintained close to a particular threshold through near continuous control, while under the reduction regime, control begins once the population reaches a certain threshold and continues until it falls below a lower pre-defined level. We discuss how to best choose the control parameters, and we provide tools that allow population managers to select reduction levels and control rates. Additional tools will be provided to assess the effect of different control regimes, in terms of population persistence and cost. In particular we consider the effects of each regime on the probability of extinction and the expected time to extinction, and compare the control methods in terms of the expected total cost of each regime over the life of the population. The usefulness of our results will be illustrated with reference to the control of a koala population inhabiting Kangaroo Island, Australia.     

Sex allocation and queen-worker conflict in polygynous ants

Summary Sex allocation theory is developed for polygynous eusocial Hymenoptera in which nests recruit their own daughters as new reproductive queens. Such restricted dispersal of females leads to the expectation of male-biased investment ratios. The expectation depends on the parameter q telling what proportion of the total contribution in the gene pool by all new queens is due to those dispersing. Under queen control the expected sex allocation, expressed as the proportion of resources invested in males, is IM =1/(1 + q). Under worker control, IM depends on the relatedness of old queens, on the number of males they have mated with, and on the proportion of males produced by workers. With single mating and no worker reproduction, the approximate predictions for IM are 1/(1 + q) when the nests have many highly related queens, 1/(1 + 2 q) when the old queens are as related as average worker nest mates, and 1/(1 + 3q) when the old queens are not related to each other at all. The observed investment ratios in polygynous ants would, on average, match values of the parameter q between 0.4 and 0.5. Values of q have not been estimated in nature. If q is smaller than 0.4, which may well be true, the observed sex allocation in polygynous ants is in fact more female-biased than predicted by the theory. This indicates that the female bias found in monogynous ants may not be exceptional and could be due to factors other than worker control of sex allocation. Because the value of q is likely to vary among species, testing the predictions of the theory requires thorough single-species studies.     

Encounter rate and task allocation in harvester ants

As conditions change, social insect colonies adjust the numbers of workers engaged in various tasks, such as foraging and nest work. This process of task allocation operates without central control; individuals respond to simple, local cues. This study investigates one such cue, the pattern of an ant's interactions with other workers. We examined how an ant's tendency to perform midden work, carrying objects to and sorting the refuse pile of the colony, is related to the recent history of the ant's brief antennal contacts, in laboratory colonies of the red harvester ant, Pogonomyrmex barbatus. The probability that an ant performed midden work was related to its recent interactions in two ways. First, the time an ant spent performing midden work was positively correlated with the number of midden workers that ant had met while it was away from the midden. Second, ants engaged in a task other than midden work were more likely to begin to do midden work when their rate of encounter per minute with midden workers was high. Cues based on interaction rate may enable ants to respond to changes in worker numbers even though ants cannot count or assess total numbers engaged in a task. Received: 1 July 1998 / Accepted: 15 November 1998     

Use of environmental isotopes and hydrochemistry as indicators for the origin of groundwater resources in El Dabaa area,northwestern coastal zone of Egypt

The EI-Dabaa area is located on the northwestern coastal zone of Egypt and is considered to be one of the most important regions for land reclamation and agriculture. In addition, it has been selected as a potential site for constructing Egypt's first nuclear power plant.In April 1989, 14 groundwater samples were collected from the area as well as collecting samples from the Mediterranean sea and from local rainwater. These samples were subjected to chemical and environmental isotope analyses. The results of the analyses for stable isotopes (oxygen-18 and deuterium) indicate that the main recharge source of the groundwater in El-Dabaa is the local precipitation during the rainy season. Variation of the environmental tritium content as well as in the chemical composition of both major cations (Na,K,Ca,Mg) and major anions (Cl,SO₄,HCO₃) between different groundwaters in the studied area reflect the high degree of inhomogeneity of the aquifer and different recharging conditions due to permeability of the water bearing formation.The chemical water type of the El-Dabaa groundwater is sodium sulphate (Na₂SO₄) and the SAR values illustrate the suitability of these groundwaters for agricultural purposes.     

Uncertainty in epidemiology and health risk and impact assessment

Environmental epidemiology and health risk and impact assessment have long grappled with problems of uncertainty in data and their relationships. These uncertainties have become more challenging because of the complex, systemic nature of many of the risks. A clear framework defining and quantifying uncertainty is needed. Three dimensions characterise uncertainty: its nature, its location and its level. In terms of its nature, uncertainty can be both intrinsic and extrinsic. The former reflects the effects of complexity, sparseness and nonlinearity; the latter arises through inadequacies in available observational data, measurement methods, sampling regimes and models. Uncertainty occurs in three locations: conceptualising the problem, analysis and communicating the results. Most attention has been devoted to characterising and quantifying the analysis—a wide range of statistical methods has been developed to estimate analytical uncertainties and model their propagation through the analysis. In complex systemic risks, larger uncertainties may be associated with conceptualisation of the problem and communication of the analytical results, both of which depend on the perspective and viewpoint of the observer. These imply using more participatory approaches to investigation, and more qualitative measures of uncertainty, not only to define uncertainty more inclusively and completely, but also to help those involved better understand the nature of the uncertainties and their practical implications.     

Uncertainty and the choice of pollution control instruments

This paper compares the relative efficiencies of pollution taxes, pollution standards, and the auctioning of pollution rights when the marginal damage function or marginal control cost are subject to uncertainty. In the first case, we find that all instruments yield the same expected social surplus. In the latter case, the choice of the optimal instrument depends, in general, on the relative elasticities of the marginal damage and marginal expected cost functions, on the way in which uncertainty enters the model, and on the distribution of the error term. Policy conclusions are derived.     

Emissions standards and ambient environmental quality standards with stochastic environmental services

Many important environmental policies involve some combination of emission controls and ambient environmental quality standards, for instance SO₂ emissions are capped under Title IV of the U.S. Clean Air Act Amendments while ambient SO₂ concentrations are limited under National Ambient Air Quality Standards (NAAQS). This paper examines the relative performance of emissions standards and ambient standards when the natural environment provides stochastic environmental services for assimilating pollution. For receiving media characterized by greater dispersion in the distribution of environmental services, the optimal emissions policy becomes more stringent, whereas the optimal ambient policy generally becomes more lax. In terms of economic performance, emissions policies are superior to ambient policies for relatively non-toxic pollutants, whereas ambient standards welfare dominate emissions standards for sufficiently toxic pollutants. In the case of combined policies that jointly implement emissions standards and ambient standards, we show that the optimal level of each standard relaxes relative to its counterpart in a unilateral policy, allowing for greater emissions levels and higher pollution concentrations in the environmental medium.     

Emissions standards and ambient environmental quality standards with stochastic environmental services

Many important environmental policies involve some combination of emission controls and ambient environmental quality standards, for instance SO₂ emissions are capped under Title IV of the U.S. Clean Air Act Amendments while ambient SO₂ concentrations are limited under National Ambient Air Quality Standards (NAAQS). This paper examines the relative performance of emissions standards and ambient standards when the natural environment provides stochastic environmental services for assimilating pollution. For receiving media characterized by greater dispersion in the distribution of environmental services, the optimal emissions policy becomes more stringent, whereas the optimal ambient policy generally becomes more lax. In terms of economic performance, emissions policies are superior to ambient policies for relatively non-toxic pollutants, whereas ambient standards welfare dominate emissions standards for sufficiently toxic pollutants. In the case of combined policies that jointly implement emissions standards and ambient standards, we show that the optimal level of each standard relaxes relative to its counterpart in a unilateral policy, allowing for greater emissions levels and higher pollution concentrations in the environmental medium.     

Foraging decisions of American robins: somatic and reproductive tradeoffs

Summary Breeding units (occupants of a nest including at least one reproductive female) within two free-living populations of the prairie vole, Microtus ochrogaster, were monitored by live-trapping at nest during two 28-h periods each week from October 1980 to March 1984. Data are presented for 281 breeding units from all seasons, at high and low population densities and during breeding and nonbreeding periods. Fifty percent of the breeding units were monogamous (single resident reproductive male and female), 27% consisted of a single reproductive female with no resident adult male and 23% included more than one resident adult male and/or female (complex units). Monogamous units were present in the same proportions during breeding and nonbreeding periods. The number of monogamous units was significantly greater at low population densities than at high densities. During winter there were relatively more complex units and fewer single female units than during the rest of the year. Monogamous pairs remained together for an average of 42 days. Seventy-eight percent of these pairs were disbanded by the death of one or both members. There were few overlaps of the home ranges of adjacent breeding units. Significantly more nests were visited by nonresident males than by females, and the intervals between visits by males were significantly shorter than those for visits by females. Males visited single female units significantly more often than units with one or more resident males. Survival of juveniles was generally very low; 38% and 34% of young males and females, respectively, that were trapped survived until 30 days of age. Of young females remaining at the natal nest at low population densities, only 17.6% were reproductively activated; 77.1% of such females became reproductively activated at high densities. All young females that dispersed from the natal nest became reproductive.