In cost-benefit analysis, natural resources, like other factors of production, should be costed as a mixture of marginal social cost of exploiting additional resources and lost marginal social benefit of forgone alternative uses, according to the way in which extra resources are made available to a project. For a nonrenewable resource, changes in future marginal social cost and marginal social benefit are likely to add significantly to the immediate elements of cost, as successively less tractable resource stocks are exploited. Of the several reasons given for ignoring these future costs, the most plausible is that technological advance justifies a heavy discount on the future. However, neither historical nor logical arguments demonstrate the inevitability of efficacious technological advance. 相似文献
The paper is concerned with the case whereby the distribution of a firm's productivity shocks changes without the knowledge of the firm. Over time the firm learns about the nature and extent of the change in the distribution of the shock and adjusts, incurring adjustment costs in the process. The long-run loss in profits (±) due to the shift in the distribution we term the equilibrium response. The transitory loss in profits, incurred while the firm is learning about the distribution shift, is termed the adjustment cost. The theory is then applied to the problem of measuring adjustment costs in the face of imperfectly observed climate change in agriculture. The empirical part of the paper involves estimating a restricted profit function for agricultural land in a five-state region of the Midwest US as a function of prices, land characteristics, actual weather realizations and expected weather. We then simulate the effect of an unobserved climate shock, where learning about the climate shock is by observing the weather and updating prior knowledge using Bayes Rule. We find adjustment costs to climate change are 1.4% of annual land rents. 相似文献
Objective: This study aimed to investigate the social and hospital costs of patients treated at a public hospital who were motorcycle crash victims.
Method: This prospective study was on 68 motorcycle riders (drivers or passengers), who were followed up from hospital admission to 6 months after the crash. A questionnaire covering quantitative and qualitative questions was administered.
Results: Motorcycle crash victims were responsible for 12% of the institution's hospital admissions; 54.4% were young (18–28 years of age); 92.6% were the drivers; 91.2% were male; and 50% used their motorcycles as daily means of transportation. Six months afterward, 94.1% needed help from someone; 83.8% had changed their family dynamics; and 73.5% had not returned to their professional activities. Among the injuries, 94.7% had some type of fracture, of which 53.5% were exposed fractures; 35.3% presented temporary sequelae; and 32.4% presented permanent sequelae. They used the surgical center 2.53 times on average, with a mean hospital stay of 18 days. The per capita hospital cost of these victims’ treatment was US$17,481.50.
Conclusion: The social and hospital costs were high, relative to the characteristics of a public institution. Temporary or permanent disability caused changes to family dynamics, as shown by the high numbers of patients who were still away from their professional activities more than 6 months afterward. 相似文献
In this paper we show that plants respond to downstream ambient water quality after controlling for permitted levels of pollution. We find if past water quality declines by one percent, plants reduce current pollution by 0.35 percent. The magnitude of this coefficient is comparable to the coefficient on permitted discharge levels i.e. regulatory stringency itself. Results are consistent with two mechanisms. First, a decline in water quality may lead to more stringent permits that would raise the cost of abatement of a plant significantly. Second, the plant is likely to be subject to increased public pressure in response to poor water quality. Indeed, as expected, the impact of water quality becomes stronger in locations with higher median household income, higher percent carpooling to work, or lower percent of manufacturing employment but surprisingly with lower median age of residents, lower percent with bachelor׳s degree or higher percent of families with children. 相似文献
Among primates, group size is highly variable. The standard ecological model assumes that better predation avoidance as group
size increases favours living in larger groups, whereas increased travel costs and reduced net food intake due to within-group
competition for resources set the upper limit. Folivorous primates, however, tend to defy this generalisation in that some
live in small groups despite low costs of feeding competition. To resolve this ’folivore paradox’, it has been suggested that folivore group size is limited by social factors such as male
harassment or infanticide, or that females can disperse more easily and thus maintain group size near optimum levels. In this
paper, we examine the effects of group size on home range size, day-journey length, activity budget and diet in wild Thomas’s
langurs (Presbytis thomasi), which live in one-male multi-female groups with a limited life cycle. We examined only data from the stable middle tenure
phase when factors such as the strength of the breeding male or the way in which groups were formed did not influence ranging
and activities. During this phase, group size affected day-journey length and home range size, and had a minor effect on diet,
but did not influence time spent feeding or resting, allogrooming or birth rates. Hence the upper limit to group size during
the middle tenure phase in Thomas’s langurs is not set by feeding competition. The folivore paradox is not due to frequent
female dispersal in Thomas’s langurs. The timing of female dispersal is not as expected if it serves to keep group sizes near
the ecological optimum, and groups seem to be below this optimum. Instead, female reproductive success is presumably maximised
in small to mid-sized groups because larger groups show a clear trend to experience higher risk of take-over, often accompanied
by infanticide. Because females can redistribute themselves among nearby groups when groups reorganise each time a new male
starts up a new group, females can keep the group small. Thus, a social factor, risk of infanticide, seems to provide the
selective advantage to small group size in Thomas’s langurs.
Received: 29 July 1999 / Revised: 17 November 1999 / Accepted: 15 October 2000 相似文献
The allocation of land to biological diversity conservation competes with other land uses and the needs of society for development, food, and extraction of natural resources. Trade‐offs between biological diversity conservation and alternative land uses are unavoidable, given the realities of limited conservation resources and the competing demands of society. We developed a conservation‐planning assessment for the South African province of KwaZulu‐Natal, which forms the central component of the Maputaland–Pondoland–Albany biological diversity hotspot. Our objective was to enhance biological diversity protection while promoting sustainable development and providing spatial guidance in the resolution of potential policy conflicts over priority areas for conservation at risk of transformation. The conservation‐planning assessment combined spatial‐distribution models for 646 conservation features, spatial economic‐return models for 28 alternative land uses, and spatial maps for 4 threats. Nature‐based tourism businesses were competitive with other land uses and could provide revenues of >US$60 million/year to local stakeholders and simultaneously help meeting conservation goals for almost half the conservation features in the planning region. Accounting for opportunity costs substantially decreased conflicts between biological diversity, agricultural use, commercial forestry, and mining. Accounting for economic benefits arising from conservation and reducing potential policy conflicts with alternative plans for development can provide opportunities for successful strategies that combine conservation and sustainable development and facilitate conservation action. Negocios de Conservación y Planificación de la Conservación en un Sitio de Importancia para la Biodiversidad 相似文献
Following a period of prolonged drought or intentional lake level drawdown, large littoral areas that once contained submersed
aquatic vegetation (SAV) are reinundated when lake levels rise. A complete assessment of the contribution made by decomposing
SAV to the in-lake phosphorus (P) concentration is important in both the management of Lake Okeechobee and understanding basic
P processes. The P contribution to the open waters of Lake Okeechobee from a rapid inundation of exposed SAV was calculated
by four methods: cores of field-desiccated SAV, cores of lab-desiccated SAV in the presence and absence of sediments, in situ
decomposition, and sequential macrophyte harvesting. P releases, given such an episodic event, were similar among the four
methods, ranging from 116±48 to 384±528 mg/m2 in the absence of sediment. When SAV is in contact with sediment, which is the realistic field situation, the amount of P
released was four times less (30±14 mg/m2) than in the absence of sediment. The calculated P releases would result in total P concentration increases in the lake from
2 to 15 μg/liter (upper 95% CI=2–25 μg/liter) in the absence of sediment; only 1 μg/liter increase was predicted when SAV
released P in contact with sediment. Thus it is unlikely that a significant rise in total P concentrations in the limnetic
zone of the lake would occur from the export of P released during the desiccation of SAV in the littoral-marsh zone during
a drawdown. 相似文献
This paper investigates whether the level of transaction costs of a Swedish agri-environmental policy measure is attributable to technical factors or whether political factors, such as lobby groups and political majorities at the county level, influence the costs. A previous study indicated that political factors may influence the level of transaction costs, but the extreme bounds analysis performed in this paper reveals that those results are fragile. It shows that three of the technical variables are robust with respect to model specifications but that none of the political variables are. Thus, no evidence can be found that political factors influence the level of transaction costs. 相似文献