Mapping the economic costs and benefits of conservation

Resources for biodiversity conservation are severely limited, requiring strategic investment. Understanding both the economic benefits and costs of conserving ecosystems will help to allocate scarce dollars most efficiently. However, although cost-benefit analyses are common in many areas of policy, they are not typically used in conservation planning. We conducted a spatial evaluation of the costs and benefits of conservation for a landscape in the Atlantic forests of Paraguay. We considered five ecosystem services (i.e., sustainable bushmeat harvest, sustainable timber harvest, bioprospecting for pharmaceutical products, existence value, and carbon storage in aboveground biomass) and compared them to estimates of the opportunity costs of conservation. We found a high degree of spatial variability in both costs and benefits over this relatively small (~3,000 km²) landscape. Benefits exceeded costs in some areas, with carbon storage dominating the ecosystem service values and swamping opportunity costs. Other benefits associated with conservation were more modest and exceeded costs only in protected areas and indigenous reserves. We used this cost-benefit information to show that one potential corridor between two large forest patches had net benefits that were three times greater than two otherwise similar alternatives. Spatial cost-benefit analysis can powerfully inform conservation planning, even though the availability of relevant data may be limited, as was the case in our study area. It can help us understand the synergies between biodiversity conservation and economic development when the two are indeed aligned and to clearly understand the trade-offs when they are not.     

Models for capacity acquisition decisions considering operational costs

In this article, we study a capacity acquisition problem by considering technology choice and operational factors in a stochastic environment. The motivation for our work comes from developments in modern flexible technologies and a problem encountered in a real industrial setting. We study the impact of operational factors such as setup times, demand patterns, and inventory/back order costs on the decisions of capacity acquisition and technology choice. We consider three alternatives in capacity and technology decisions: (i) a flexible system, (ii) a dedicated system, and (iii) a combination of these two systems. For each system, we develop a model that integrates investment decisions and operational decisions to determine an optimal amount of capacity to purchase and the time and the types of parts to produce. The objective is to minimize the capacity acquisition cost at the beginning of the planning horizon and the total expected operational costs over an infinite planning horizon. To solve the problem in this article, a solution procedure is proposed. Managerial insights are also derived from extensive computational results.     

Optimal traits when there are several costs: the interaction of mortality and energy costs in determining foraging behavior

I analyzed the interaction of different types of costs in determiningoptimal behavior using mathematical models. The analysis concentrateson foraging behavior and asks (1) whether the cost factor thathas the greatest effect on fitness generally has the greatesteffect on optimal trait values and (2) whether increasing thesize of one type of cost makes the optimal behavior absolutelyor relatively more sensitive to that cost. The foraging costsconsidered are energy expenditure, predation risk, and othermortality factors. It is shown that increasing the magnitudeof one cost often decreases the relative and absolute sensitivityof the optimal foraging strategy to that cost. The relativefitness effects of different costs generally differ from therelative sensitivities of the optimal strategies to the costfactors. Researchers should therefore measure the shapes ofcost curves rather than their average magnitudes to determinewhich of several costs can be ignored in cost-benefit analyses.     

Nutrient limitation and stoichiometry of carnivorous plants

The cost-benefit model for the evolution of carnivorous plants posits a trade-off between photosynthetic costs associated with carnivorous structures and photosynthetic benefits accrued through additional nutrient acquisition. The model predicts that carnivory is expected to evolve if its marginal benefits exceed its marginal costs. Further, the model predicts that when nutrients are scarce but neither light nor water is limiting, carnivorous plants should have an energetic advantage in competition with non-carnivorous plants. Since the publication of the cost-benefit model over 20 years ago, marginal photosynthetic costs of carnivory have been demonstrated but marginal photosynthetic benefits have not. A review of published data and results of ongoing research show that nitrogen, phosphorus, and potassium often (co-)limit growth of carnivorous plants and that photosynthetic nutrient use efficiency is 20 - 50 % of that of non-carnivorous plants. Assessments of stoichiometric relationships among limiting nutrients, scaling of leaf mass with photosynthesis and nutrient content, and photosynthetic nutrient use efficiency all suggest that carnivorous plants are at an energetic disadvantage relative to non-carnivorous plants in similar habitats. Overall, current data support some of the predictions of the cost-benefit model, fail to support others, and still others remain untested and merit future research. Rather than being an optimal solution to an adaptive problem, botanical carnivory may represent a set of limited responses constrained by both phylogenetic history and environmental stress.     

MUTUAL MATE CHOICE AND SEX DIFFERENCES IN CHOOSINESS

Sexual competition is associated closely with parental care because the sex providing less care has a higher potential rate of reproduction, and hence more to gain from competing for multiple mates. Sex differences in choosiness are not easily explained, however. The lower-caring sex (often males) has both higher costs of choice, because it is more difficult to find replacement mates, and higher direct benefits, because the sex providing more care (usually females) is likely to exhibit more variation in the quality of contributions to the young. Because both the costs and direct benefits of mate choice increase with increasing parental care by the opposite sex, general predictions about sex difference in choosiness are difficult. Furthermore, the level of choosiness of one sex will be influenced by the choosiness of the other. Here, we present an ESS model of mutual mate choice, which explicitly incorporates differences between males and females in life history traits that determine the costs and benefits of choice, and we illustrate our results with data from species with contrasting forms of parental care. The model demonstrates that sex differences in costs of choice are likely to have a much stronger effect on choosiness than are differences in quality variation, so that the less competitive sex will commonly be more choosy. However, when levels of male and female care are similar, differences in quality variation may lead to higher levels of both choice and competition in the same sex.     

Evolution of cooperation with shared costs and benefits

The quest to determine how cooperation evolves can be based on evolutionary game theory, in spite of the fact that evolutionarily stable strategies (ESS) for most non-zero-sum games are not cooperative. We analyse the evolution of cooperation for a family of evolutionary games involving shared costs and benefits with a continuum of strategies from non-cooperation to total cooperation. This cost-benefit game allows the cooperator to share in the benefit of a cooperative act, and the recipient to be burdened with a share of the cooperator's cost. The cost-benefit game encompasses the Prisoner's Dilemma, Snowdrift game and Partial Altruism. The models produce ESS solutions of total cooperation, partial cooperation, non-cooperation and coexistence between cooperation and non-cooperation. Cooperation emerges from an interplay between the nonlinearities in the cost and benefit functions. If benefits increase at a decelerating rate and costs increase at an accelerating rate with the degree of cooperation, then the ESS has an intermediate level of cooperation. The game also exhibits non-ESS points such as unstable minima, convergent-stable minima and unstable maxima. The emergence of cooperative behaviour in this game represents enlightened self-interest, whereas non-cooperative solutions illustrate the Tragedy of the Commons. Games having either a stable maximum or a stable minimum have the property that small changes in the incentive structure (model parameter values) or culture (starting frequencies of strategies) result in correspondingly small changes in the degree of cooperation. Conversely, with unstable maxima or unstable minima, small changes in the incentive structure or culture can result in a switch from non-cooperation to total cooperation (and vice versa). These solutions identify when human or animal societies have the potential for cooperation and whether cooperation is robust or fragile.     

Batch sizes and lead-time performance in flexible manufacturing systems

Production lead-time performance in flexible manufacturing systems is influenced by several factors which include: machine groupings, demand rates, machine processing rates, product batching, material handling system capacity, and so on. Hence, control of lead-time performance can be affected through the manipulation of one or more of these variables. In this article, we investigate the potential of batch sizing as a control variable for lead-time performance through the use of a queueing network model. We establish a functional relationship between the two variables, and incorporate the relationship in an optimization model to determine the optimal batch size(s) which minimizes the sum of annual work-in-process inventory and final inventory costs. The nonlinear batch sizing problem which results is solved by discrete optimization via marginal analysis. Results show that batch sizing can be a cheap and effective variable for controlling flexible manufacturing system throughput.     

Freight consolidation in intermodal networks with reloads

Intermodal networks offer much flexibility in transport planning, and have the potential to efficiently consolidate goods, even if these goods have distinct pickup locations and destinations. Typically, there is an abundant amount of feasible routes and consolidation opportunities, which makes it challenging to quickly identify good solutions. We propose a planning algorithm for dynamic pickup- and delivery problems in intermodal networks, where freight is consolidated by means of reloads to reduce both costs and emissions. Based on an enumerative arc-expansion procedure, a large number of intermodal routes is generated for each order, of which we store the k best. We subsequently evaluate consolidation opportunities for the k best routes by applying a decision tree structure, taking into account reload operations, timetables, and synchronization of departure windows. Compared to direct road transport, numerical experiments on various virtual problem instances show an average cost saving of 34 %, and an average reduction in \(CO_2\) emissions of 30 %. Furthermore, we test our algorithm on a real-life case of a leading logistics service provider based in the Netherlands, which yields significant benefits as well, both in terms of costs and environmental impact.     

Equilibrium models in multimodal container transport systems

Optimizing the performance of multimodal freight transport networks involves adequately balancing the interplay between costs, volumes, times of departure and arrival, and times of travel. In order to study this interplay, we propose an assignment model that is able to efficiently determine flows and costs in a multimodal network. The model is based on a so-called user equilibrium principle, which is at the basis of Dynamic Traffic Assignment problems. This principle takes into account transport demands to be shipped using vehicles that transport single freight units (such as trucks) or multiple freight units (such as trains and barges, where demand should be bundled to reach efficient operations). Given a particular demand, the proposed model provides an assignment of the demand over the available modes of transport. The outcome of the model, i.e., the equilibrium point, minimizes users’ generalized costs, expressed as a function of mode, travel time and related congestion, and waiting time for bundling sufficient demand in order to fill a vehicle. The model deals with these issues across a doubly-dynamic time scale and in an integrated manner. One dynamic involves a learning dynamic converging towards an equilibrium (day-to-day) situation, reflecting the reaction of the players towards the action of the others. Another dynamic considers the possible departure time that results in minimum expected costs, also due to the fact that players mutually influence each other on the choice of departure times, due to congestion effects and costs for early/late arrival of freight units. This is a choice within a given time horizon such as a day or a week. We present a study on the influence and sensitivity of different model parameters, in order to analyse the implications on strategic decisions, fostering a target modal share for freight transportation. We also study under which conditions the different modes can be substitutes for each other.     

海洋生态修复:概念、类型与实施路径选择

生态修复是我国生态文明建设的重要内容。在对生态修复相关概念梳理的基础上,从公共物品治理视角对海洋生态修复主体、修复标准、修复路径及修复措施保障等关键环节进行论述,研究表明：污染和破坏者作为赔偿型海洋生态修复的主体,可通过自行修复和委托修复等方式,将受损海洋生态修复到破坏前的基线水平;国家作为补偿型海洋生态修复的主体,依据边际成本收益分析法确定最优修复规模,通过政府市场采购和创建市场等经济激励型路径实施生态修复以增加公众福利。未来我国海洋生态修复应重点关注修复的资金保障、监督制度以及生态修复的技术研发和修复完成后的成本收益评估等。     

Active selection for large guppies, Poecilia reticulata, by the pike cichlid, Crenicichla saxatilis

Size-selective predation has been proposed to be one important evolutionary force shaping life-history traits in guppies ( Poecilia reticulata ). Populations living in the presence of the ring-tailed pike cichlid ( Crenicichla saxatilis ) are smaller, mature earlier, allocate more energy to offspring and get more and smaller young than guppies in localities without Crenicichla . We investigated if Crenicichla saxatilis is a size-selective predator, if the selectivity is a result of active choice and if the optimal prey size can be explained according to an optimal foraging model. In single-prey experiments we quantified the predators' pre-capture costs (time), capture success, and post-capture costs (time) for four different prey sizes spanning from 10 to 40 mm total length. To see which of the components of the prey cycle the predator takes into account for its choice, we then predicted prey values and optimal prey size with 6 different models that included one or more of the prey cycle components.
In two multiple prey experiments, the cichlids were given the choice of the two and four different prey sizes simultaneously. Crenicichla saxatilis actively selected the largest guppies in both cases. The three prey-value functions that included handling time (post-capture cost) did not accurately predict the prey choice. Instead the prey-value functions that took into account pre-capture cost (approach and attack time) were able to correctly predict the choice of the largest guppy size, suggesting that pre-capture costs may be more important than post-capture costs for prey choice in Crenicichla saxatilis . The study confirms that Crenicichla saxatilis is a size-selective predator selecting large guppies, while earlier evidence for selectivity for large prey in Crenicichla cichlids has been weak and equivocal. Our result strengthen the possibility that size-selective predation is a mechanism in life-history evolution in guppies.     

Incorporating Science,Technology, Fairness,and Accountability in Environmental,Health, and Safety Decisions

The Precautionary Principle is in sharp political focus today because (1) the nature of scientific uncertainty is changing and (2) there is increasing pressure to base governmental action on more “rational” schemes, such as cost-benefit analysis and quantitative risk assessment, the former being an embodiment of ‘rational choice theory’ promoted by the Chicago school of law and economics. The Precautionary Principle has been criticized as being both too vague and too arbitrary to form a basis for rational decision making. The assumption underlying this criticism is that any scheme not based on cost-benefit analysis and risk assessment is both irrational and without secure foundation in either science or economics. This paper contests that view and makes explicit the rational tenets of the Precautionary Principle within an analytical framework as rigorous as uncertainties permit, and one that mirrors democratic values embodied in regulatory, compensatory, and common law. Unlike other formulations that reject risk assessment, this paper argues that risk assessment can be used within the formalism of tradeoff analysis—a more appropriate alternative to traditional cost-benefit analysis and one that satisfies the need for well-grounded public policy decision making. This paper will argue that the precautionary approach is the most appropriate basis for policy, even when large uncertainties do not exist, especially where the fairness of the distributions of costs and benefits of hazardous activities and products are a concern. Furthermore, it will offer an approach to making decisions within an analytic framework, based on equity and justice, to replace the economic paradigm of utilitarian cost-benefit analysis.     

No Inbreeding Avoidance by Female Burying Beetles Regardless of Whether They Encounter Males Simultaneously or Sequentially

Inbreeding avoidance reduces the probability that an individual will mate with a related partner, thereby lowering the risk that it produces inbred offspring suffering from inbreeding depression. Inbreeding avoidance can occur through several mechanisms, including active mate choice, polyandry and sex‐biased dispersal. Here, we focus on the role of active mate choice as a mechanism for inbreeding avoidance. Recent evidence suggests that the experimental design used in mate choice experiments (i.e. simultaneous versus sequential choice) can have a strong impact on the strength of the reported mating preferences. In this study, we examine whether similar effects of experimental design also apply in the context of inbreeding avoidance. To this end, we designed two experiments on the burying beetle Nicrophorus vespilloides that matched two different contexts under which females encounter potential mates in the wild; that is, when females encounter males simultaneously and sequentially. We found that females were as likely to mate with related and unrelated males regardless of whether they encountered male partners simultaneously or sequentially. Thus, our study provides no evidence for inbreeding avoidance in this species, and suggests that the number of mates present did not influence the degree of inbreeding avoidance. We discuss potential explanations for the lack of inbreeding avoidance through mate choice, including lack of mechanisms for recognizing close relatives, low costs and/or low risks of inbreeding and the presence of other inbreeding avoidance mechanisms, such as sex‐biased dispersal and polyandry coupled with post‐copulatory mate choice.     

The economics of schistosomiasis chemotherapy

The optimal choice o f chemotherapy regime arises in the design o f every schistosomiasis control programme. This choice is o f particular contemporary interest for two reasons. At one extreme the development of effective single-dose oral drugs such as praziquantel and oxamniquine makes mass chemotherapy a practical option. At the other extreme there has been a revival o f advocacy for some form o f selective treatment. But all developing countries that contemplate schistosomiasis control face severe budget constraints, requiring careful analysis o f the economics o f chemotherapy. In this article, Nick Prescott presents a generalized framework For resource allocation in schistosomiasis chemotherapy, demonstrating that the optimal choice o f chemotherapy regime depends critically on the level of budget constraint, the unit costs o f screening and treatment, and rates o f compliance with screening and chemotherapy-all factors which are usually neglected in the choice o f control strategy.     

Integration of order picking and vehicle routing in a B2C e-commerce context

E-commerce sales are increasing every year and customers who buy goods on the Internet have high service level expectations. In order to meet these expectations, a company’s logistics operations need to be performed carefully. Optimizing only internal warehouse processes will often lead to suboptimal solutions. The interrelationship between the order picking process and the delivery process should not be ignored. Therefore, in this study, an order picking problem and a vehicle routing problem with time windows and release dates are solved simultaneously using a single optimization framework. To the best of our knowledge, it is the first time that an order picking problem and a vehicle routing problem are integrated. A mixed integer linear programming formulation for this integrated order picking-vehicle routing problem (OP-VRP) is provided. The integrated OP-VRP is solved for small instances and the results are compared to these of an uncoordinated approach. Computational experiments show that integration can lead to cost savings of 14% on average. Furthermore, higher service levels can be offered by allowing customers to request their orders later and still get delivered within the same time windows.     

A sex-specific trade-off between mating preferences for genetic compatibility and body size in a cichlid fish with mutual mate choice

Mating preferences for genetic compatibility strictly depend on the interplay of the genotypes of potential partners and are therein fundamentally different from directional preferences for ornamental secondary sexual traits. Thus, the most compatible partner is on average not the one with most pronounced ornaments and vice versa. Hence, mating preferences may often conflict. Here, we present a solution to this problem while investigating the interplay of mating preferences for relatedness (a compatibility criterion) and large body size (an ornamental or quality trait). In previous experiments, both sexes of Pelvicachromis taeniatus, a cichlid fish with mutual mate choice, showed preferences for kin and large partners when these criteria were tested separately. In the present study, test fish were given a conflicting choice between two potential mating partners differing in relatedness as well as in body size in such a way that preferences for both criteria could not simultaneously be satisfied. We show that a sex-specific trade-off occurs between mating preferences for body size and relatedness. For females, relatedness gained greater importance than body size, whereas the opposite was true for males. We discuss the potential role of the interplay between mating preferences for relatedness and body size for the evolution of inbreeding preference.     

Optimal control of hepatitis C antiviral treatment programme delivery for prevention amongst a population of injecting drug users

In most developed countries, HCV is primarily transmitted by injecting drug users (IDUs). HCV antiviral treatment is effective, and deemed cost-effective for those with no re-infection risk. However, few active IDUs are currently treated. Previous modelling studies have shown antiviral treatment for active IDUs could reduce HCV prevalence, and there is emerging interest in developing targeted IDU treatment programmes. However, the optimal timing and scale-up of treatment is unknown, given the real-world constraints commonly existing for health programmes. We explore how the optimal programme is affected by a variety of policy objectives, budget constraints, and prevalence settings. We develop a model of HCV transmission and treatment amongst active IDUs, determine the optimal treatment programme strategy over 10 years for two baseline chronic HCV prevalence scenarios (30% and 45%), a range of maximum annual budgets (￡50,000-300,000 per 1,000 IDUs), and a variety of objectives: minimising health service costs and health utility losses; minimising prevalence at 10 years; minimising health service costs and health utility losses with a final time prevalence target; minimising health service costs with a final time prevalence target but neglecting health utility losses. The largest programme allowed for a given budget is the programme which minimises both prevalence at 10 years, and HCV health utility loss and heath service costs, with higher budgets resulting in greater cost-effectiveness (measured by cost per QALY gained compared to no treatment). However, if the objective is to achieve a 20% relative prevalence reduction at 10 years, while minimising both health service costs and losses in health utility, the optimal treatment strategy is an immediate expansion of coverage over 5-8 years, and is less cost-effective. By contrast, if the objective is only to minimise costs to the health service while attaining the 20% prevalence reduction, the programme is deferred until the final years of the decade, and is the least cost-effective of the scenarios.     

Chronic measurement of cardiac output in conscious mice

We describe the feasibility of chronic measurement of cardiac output (CO) in conscious mice. With the use of gas anesthesia, mice >30 g body wt were instrumented either with transit-time flow probes or electromagnetic probes placed on the ascending aorta. Ascending aortic flow values were recorded 6-16 days after surgery when probes had fully grown in. In the first set of experiments, while mice were under ketamine-xylazine anesthesia, estimates of stroke volume (SV) obtained by the transit-time technique were compared with those simultaneously obtained by echocardiography. Transit-time values of SV were similar to those obtained by echocardiography. The average difference +/- SD between the methods was 2 +/- 7 microl. In the second set of studies, transit-time values of CO were compared with those obtained by the electromagnetic flow probes. In conscious resting conditions, estimates +/- SD) of cardiac index (CI) obtained by the transit-time and electromagnetic flow probes were 484 +/- 119 and 531 +/- 103 ml x min(-1) x kg body wt(-1), respectively. Transit-time flow probes were also implanted in mice with a myocardial infarction (MI) induced by ligation of a coronary artery 3 wk before probe implantation. In these MI mice (n = 7), average (+/- SD) resting and stimulated (by volume loading) values of CO were significantly lower than in noninfarcted mice (n = 15) (resting CO 16 +/- 3 vs. 20 +/- 4 ml/min; stimulated CO 20 +/- 5 vs. 26 +/- 6 ml/min). Finally, using transfer function analysis, we found that, in resting conditions for both intact and MI mice, spontaneous variations in CO (> 0.1 Hz) were mainly due to those occurring in SV rather than in heart rate. These data indicate that CO can be measured chronically and reliably in conscious mice, also in conditions of heart failure, and that variations in preload are an important determinant of CO in this species.     

A carbon cost-gain model explains the observed patterns of xylem safety and efficiency

Efficient water transport from the soil to the leaves is essential for plant function, while building and maintaining the water transport structure in the xylem require a major proportion of the assimilated carbon of the tree. Xylem transport also faces additional challenges as water in the xylem is under tension and therefore cavitation cannot be completely avoided. We constructed a model that calculates the xylem structure that maximizes carbon-use efficiency while simultaneously taking into account pit structure in increasing the resistance to water transport and constricting the spreading of embolisms. The optimal xylem structure predicted by the model was found to correspond well to the generally observed trends: xylem conduits grew in size from the apex towards the base while simultaneously decreasing in number, and vulnerability to cavitation increased with conduit size. These trends were caused primarily by the axial water potential gradient in the xylem. The pits have to be less porous near the apex where water potential is lower to restrict the spreading of embolisms, while whole-plant carbon-use efficiency demands that conduit size decreases and conduit number increases simultaneously. The model predictions remained qualitatively the same regardless of the exact optimality criterion used for defining carbon-use efficiency.     

Costs and cost-minimisation analysis.

Whatever kind of economic evaluation you plan to undertake, the costs must be assessed. In health care these are first of all divided into costs borne by the NHS (like drugs), by patients and their families (like travel), and by the rest of society (like health education). Next the costs have to be valued in monetary terms; direct costs, like wages, pose little problem, but indirect costs (like time spent in hospital) have to have values imputed to them. And that is not all: costs must be further subdivided into average, marginal, and joint costs, which help decisions on how much of a service should be provided. Capital costs (investments in plant, buildings, and machinery) are also important, as are discounting and inflation. In this second article in the series Ray Robinson defines the types of costs, their measurement, and how they should be valued in monetary terms.