Recycling in the USA : Vision and reality

In 1978 the US Environmental Protection Agency contracted Mathtech Incorporated to identify the impediments to recycling and evaluate their economic effects. The facilities studied represented a cross-section of recycling technologies, ownership types, geographical locations, and recovered products. It was discovered that none of the facilities was economical in the sense of providing the least-cost mode of disposal for municipal solid waste, and all of them suffered net losses in recent operations. Indications were that financial performance would improve slightly. A major deterrent to economical operations was the availability of lower-cost disposal by landfill.     

LAND TREATMENT IN WATERSHED PROGRAM AREAS1

Several types of watershed program areas, principally but not solely those operated under authority of the Watershed Protection and Flood Prevention Act, are greatly altering the American landscape for good. While structural measures tend to be the most spectacular feature of these watersheds, land treatment measures (soil, water, woodland, and wildlife conservation practices) actually are basic to the long term stability and maximum contributions of these watershed programs.     

ROLE OF MODELS IN GROUNDWATER MANAGEMENT1

To answer the difficult question of how to integrate operation of ground and surface water supplies into their management plans, the decision-makers must be able to predict the effects of various alternative modes of operation and meteorological conditions on the groundwater basin. Many types of models have been used for simulating the behavior of groundwater basins under these changes. Analog simulators, analog computers, and digital computers have been employed for model development. To achieve plausible models, detailed hydraulic and hydrologic characteristics are required, such as data on transmissivity, storage, and net deep percolation. These data are used in the equations that form the model. Water quality, which cannot be separated from quantity, deserves equal consideration. Recently, considerable efforts have been made to develop water quality prediction tools through the use of modeling techniques.     

Strong self-limitation promotes the persistence of rare species

Theory has recognized a combination of niche and neutral processes each contributing, with varying importance, to species coexistence. However, long-term persistence of rare species has been difficult to produce in trait-based models of coexistence that incorporate stochastic dynamics, raising questions about how rare species persist despite such variability. Following recent evidence that rare species may experience significantly different population dynamics than dominant species, we use a plant community model to simulate the effect of disproportionately strong negative frequency dependence on the long-term persistence of the rare species in a simulated community. This strong self-limitation produces long persistence times for the rare competitors, which otherwise succumb quickly to stochastic extinction. The results suggest that the mechanism causing species to be rare in this case is the same mechanism allowing those species to persist.     

What does team–member exchange bring to the party? A meta‐analytic review of team and leader social exchange

Both leader–member exchange (LMX) and team–member exchange (TMX) measure the quality of reciprocal exchange among employees in the workplace. Although LMX focuses on supervisor–subordinate relationships while TMX examines the relationships among team members, both have theory‐based and empirically proven relations with workplace outcomes such as job performance, organizational commitment, job satisfaction, and turnover intentions. However, it is not yet known which has more of an impact on such workplace outcomes—specifically, it is not clear if an employee's time is best spent developing vertical relationships among supervisors and subordinates (LMX) or on the horizontal relationships among team members (TMX). Accordingly, this meta‐analysis explores the incremental validity and relative importance of these two social exchange‐based constructs. The theoretical logic underlying LMX and TMX is clarified, and the parameter estimates between LMX, TMX, and work outcomes are reported. Results demonstrate that TMX shows incremental validity above and beyond LMX for some outcomes (organizational commitment and job satisfaction), but not others (job performance and turnover intentions). Also, LMX shows greater relative importance across all four outcomes. In sum, the clarification of the theoretical and empirical landscape lays a foundation for recommendations for future research. Copyright © 2013 John Wiley & Sons, Ltd.     

Impacts of Human Behavioral Heterogeneity on the Benefits of Probabilistic Flood Warnings: An Agent‐Based Modeling Framework

Flood forecasts and warnings are intended to reduce flood‐related property damages and loss of human life. Considerable research has improved flood forecasting accuracy (e.g., more accurate prediction of the occurrence of flood events) and lead time. However, the delivery of improved forecast information alone is not necessarily sufficient to reduce flood damage and loss of life, as people have varying responses and reactions to flood warnings. This study develops an agent‐based modeling framework that evaluates the impacts of heterogeneity in human behaviors (i.e., variation in behaviors in response to flood warnings), as well as residential density, on the benefits of flood warnings. The framework is coupled with a traffic model to simulate evacuation processes within a road network under various flood warning scenarios. The results show the marginal benefit associated with providing better flood warnings is significantly constrained if people behave in a more risk‐tolerant manner, especially in high‐density residential areas. The results also show significant impacts of human behavioral heterogeneity on the benefits of flood warnings, and thus stress the importance of considering human behavioral heterogeneity in simulating flood warning‐response systems. Further study is suggested to more accurately model human responses and behavioral heterogeneity, as well as to include more attributes of residential areas to estimate and improve the benefits of flood warnings.     

Interaction of Population Growth,Industrial Growth and Pollution Control

A model is developed which predicts the level of pollution as a function of time given the rate of waste production and the persistence of the pollutant. In general, waste production is a function of the population density and the degree of industrialization of a society. With pollution control programs it is possible to reduce the per capita waste production for a given degree of industrialization. The model demonstrates that in a growth economy such as that of the United States, pollution control programs by themselves only delay the inevitable increase in pollution levels. In the long run population and industrial growth are incompatible with pollution control.