Time preference,the environment and the interests of future generations

The behavior of individuals currently living will generally have long-term consequences that affect the well-being of those who will come to live in the future. Intergenerational interdependencies of this nature raise difficult moral issues because only the current generation is in a position to decide on actions that will determine the nature of the world in which future generations will live. Although most are willing to attach some weight to the interests of future generations, many would argue that it is not necessary to treat these interests as equivalent to those of the current generation. A common approach in this context is to use a system of discounting to evaluate future benefits and harms. This paper assesses the logic of discounting drawing on the writings of economists and philosophers. Much of the economic literature concerns the choice of an appropriate social discount rate. The social discount rate can be taken to reflect beliefs about the rights of future generations, a subject that has been extensively debated in the phioosophic literature. The writings of both economists and philosophers concerned with the weight to attach to the interests of future generations are reviewed and evaluated in this paper and the implications for environmental policy are discussed.     

Applying knowledge-based methods to design and implement an air quality workshop

In response to protection needs in class I wilderness areas, forest land managers of the USDA Forest Service must provide input to regulatory agencies regarding air pollutant impacts on air quality-related values. Regional workshops have been convened for land managers and scientists to discuss the aspects and extent of wilderness protection needs. Previous experience with a national workshop indicated that a document summarizing workshop discussions will have little operational utility. An alternative is to create a knowledge-based analytical system, in addition to the document, to aid land managers in assessing effects of air pollutants on wilderness. Knowledge-based methods were used to design and conduct regional workshops in the western United States. Extracting knowledge from a large number of workshop participants required careful planning of workshop discussions. Knowledge elicitation methods helped with this task. This knowledge-based approach appears to be effective for focusing group discussions and collecting knowledge from large groups of specialists.     

Disadvantaged consumers — can planning respond?

The development of new forms of retailing has brought material advantage to a majority of the population, in terms of greater choice, comfort and cheapness in shopping. These benefits are greatest in supermarkets and hypermarkets. However, these outlets are not evenly distributed over the urban area when compared to smaller, traditional stores. As a result the population has varying degrees of access to them. As strong disparities in levels of income, and mobility already exist, concern has been expressed over the growing inequalities between the poorer, minority sections of the population, and the rest. This paper identifies groups of consumers who can be described as ‘disadvantaged’ in terms of shopping and looks at the spatial implications of consumer deprivation and examines possible solutions to these problems.     

Developing inventory and monitoring programs based on multiple objectives

Resource inventory and monitoring (I&M) programs in national parks combine multiple objectives in order to create a plan of action over a finite time horizon. Because all program activities are constrained by time and money, it is critical to plan I&M activities that make the best use of available agency resources. However, multiple objectives complicate a relatively straightforward allocation process. The analytic hierarchy process (AHP) offers a structure for multiobjective decision making so that decision-makers’ preferences can be formally incorporated in seeking potential solutions. Within the AHP, inventory and monitoring program objectives and decision criteria are organized into a hierarchy. Pairwise comparisons among decision elements at any level of the hierarchy provide a ratio scale ranking of those elements. The resulting priority values for all projects are used as each project’s contribution to the value of an overall I&M program. These priorities, along with budget and personnel constraints, are formulated as a zero/one integer programming problem that can be solved to select those projects that produce the best program. An extensive example illustrates how this approach is being applied to I&M projects in national parks in the Pacific Northwest region of the United States. The proposed planning process provides an analytical framework for multicriteria decisionmaking that is rational, consistent, explicit, and defensible.     

Better environmental future in Europe through environmental auditing?

environmental auditing must be rejected if the aim is to make companies introduce a specific management concept. Rather, it is preferable to leave the search for effective environmental protection strategies to the competitive system, especially since the criteria for environment-oriented management in the European Community audit proposal are without substance. Environmental auditing can, however, assume a complementary function in the framework of an overall environmental policy if it is designed as an information tool with which companies provide information on the development of environmental problems deriving from their manufacturing processes and products. However, the model required to establish a framework of quantity and evaluation criteria is not available. Further, auditing does not cover products. Similarly, there are no proposals defining the evaluation procedure for ecological resource scarcity. Thus, the attempt of the Commission of the European Communities to create the elementary prerequisites for consistent and verifiable environmental auditing in the corporate sector has failed.     

Decision analysis of polluted sites — a fuzzy set approach

A decision analysis based model (DAPS 1.0, Decision Analysis of Polluted Sites) has been developed to evaluate risks that polluted sites might pose to human health. Pollutants present in soils and sediments can potentially migrate from source to receptor(s), via different pathways. In the developed model, pathways are simulated via transport models (i.e. groundwater transport model, runoff-erosion model, air diffusion model, and sediment diffusion, and resuspension model in water bodies). Humans can be affected by pollutant migration through land and water use. Health risks can arise from ingestion of and dermal contact with polluted water and soil, as well as through inhalation of polluted air. Quantitative estimates of risks are calculated for both carcinogenic and non-carcinogenic pollutants. Being very heterogeneous, soil and sediment systems are characterized by uncertain parameters. Concepts of fuzzy set theory have been adopted to account for uncertainty in the input parameters which are represented by fuzzy numbers. An inference model using fuzzy logic has been constructed for reasoning in the decision analysis.     

Cross-shelf variation in calanoid copepod production during summer 1996 off the Oregon coast, USA

The fecundity of nine species of adult female calanoid copepods, and molting rates for copepodite stages of Calanus marshallae were measured in 24 h shipboard incubations from samples taken during the upwelling season off the Oregon coast. Hydrographic and chlorophyll measurements were made at approximately 300 stations, and living zooplankton were collected at 36 stations on the continental shelf (<150 m depth) and 37 stations offshore of the shelf (>150 m depth) for experimental work. In our experiments, maximum egg production rates (EPR) were observed only for Calanus pacificus and Pseudocalanus mimus, 65.7 and 3.9 eggs fem^-1 day^-1 respectively, about 95% of the maximum rates known from published laboratory observations. EPR of all other copepod species (e.g., C. marshallae, Acartia longiremis and Eucalanus californicus) ranged from 3% to 65% of maximum published rates. Fecundity was not significantly related to body weight or temperature, but was significantly correlated with chlorophyll a concentration for all species except Paracalanus parvus and A. longiremis. Copepod biomass and production in on-shelf waters was dominated by female P. mimus and C. marshallae, accounting for 93% of the adult biomass (3.1 mg C m^-3) and 81% of the adult production (0.19 mg C m^-3 day^-1). Biomass in the off-shelf environment was dominated by female E. californicus, P. mimus, and C. pacificus, accounting for 95% of the adult biomass (2.2 mg C m^-3) and 95% of the adult production (0.08 mg C m^-3 day^-1). Copepodite (C1-C5) production was estimated to be 2.1 mg C m^-3 day^-1 (on-shelf waters) and 1.2 mg C m^-3 day^-1 (off-shelf water). Total adult + juvenile production averaged 2.3 mg C m^-3 day^-1 (on-shelf waters) and 1.3 mg C m^-3 day^-1 (off-shelf waters). We compared our measured female weight-specific growth rates to those predicted from the empirical models of copepod growth rates of Huntley and Lopez [Am Nat (1992) 140:201-242] and Hirst and Lampitt [Mar Biol (1998) 132:247-257]. Most of our measured values were lower than those predicted from the equation of Huntley and Lopez. We found good agreement with Hirst and Lampitt for growth rates <0.10 day^-1 but found that their empirical equations underestimated growth at rates >0.10 day^-1. The mismatch with Hirst and Lampitt resulted because some of our species were growing at maximum rates whereas their composite empirical equations predict "global" averages that do not represent maximum growth rates.     

When r-selection may not predict introduced-species proliferation: predation of a nonnative oyster.

Predicting outcomes of species introductions may be enhanced by integrating life-history theory with results of contained experiments that compare ecological responses of exotic and analogue native species to dominant features of the recipient environment. An Asian oyster under consideration for introduction to the Chesapeake Bay, USA, the rapidly growing Suminoe oyster (Crassostrea ariakensis), may not be as successful an invader as its r-selected life history suggests if the trade-off for rapid growth and maturation is lower investment in defenses against blue crab (Callinectes sapidus) predation than the native Eastern oyster (Crassostrea virginica). In laboratory trials, blue crabs simultaneously offered equal numbers of Suminoe and Eastern oysters consumed more nonnatives, irrespective of whether the crabs had previous experience with Suminoe oysters as prey. Satiated blue crabs consumed nearly three times as many Suminoe oysters as Eastern oysters of 25-mm shell height, and eight times as many of 35-mm shell height. Despite blue crabs consuming small (30 mm) Suminoe oysters at twice the rate of large (40 mm) Suminoe oysters, when 40-mm Suminoe were paired with 30-mm Eastern oysters, seven times as many of the larger (Suminoe) oysters were consumed. The greater susceptibility of C. ariakensis than C. virginica to blue crab predation appears to be based upon the biomechanics of shell strength rather than active selection of a more attractive food. Much less force was required to crush shells of Suminoe than Eastern oysters of similar shell height. Tissue transplant experiments demonstrated greater predation on oyster tissues in weaker C. ariakensis shells independent of tissue identity, and duration of handling time before rejection of C. virginica exceeded the time to crush C. ariakensis. These results, coupled with the present importance of blue crab predation in limiting recovery of native Eastern oysters, imply a role for blue crabs in inhibiting Suminoe oysters, if introduced, from attaining high adult densities required to restore a fishery, provide appreciable reef habitat, and reduce turbidity through filtration. Thus, in high-predation environments, allocation of resources to rapid growth and development rather than to predation defenses reflects a life-history trade-off that may promote early stages of invasion, yet prevent attainment of dense adult populations.