How much heterogeneity? Flow versus area from a big data perspective

Over the past 10 years, there has been an increased recognition that matrix diffusion processes are a significant factor controlling the success of groundwater remediation. New field techniques and modeling tools have, consequently, been developed to understand how contaminants diffuse into and then out of low‐permeability (“low‐k”) zones and assess the resulting impact on groundwater quality. Matrix diffusion, in turn, is driven by one key factor: geologic heterogeneity. The importance of heterogeneity is being emphasized in the groundwater field by general rules of thumb such as “90% of the mass flux occurs in 10%‐20% of the cross‐sectional area” and conceptual models that show most of the groundwater flow occurs through the aquifer's “mobile porosity” which just a small fraction of commonly used effective porosity values (between 0.02 and 0.10 for mobile porosity vs. 0.25 for effective porosity). For this study, 141 boring logs from 43 groundwater remediation sites were evaluated to develop an empirically based estimate of the groundwater flow versus aquifer cross‐sectional area to confirm or reject the general flow versus area rules of thumb. This study indicated that at these 43 sites, an average of 30% of the cross‐sectional area carried 90% of the groundwater flow. Our flow‐only analysis does provide moderate (but not confirmatory) support for the “mobile porosity” concept with an estimated representative mobile porosity value of about 0.11 at the 43 sites.     

Practicing food justice at Dig Deep Farms & Produce,East Bay Area,California: self-determination as a guiding value and intersections with foodie logics

This article describes Dig Deep Farms & Produce, a food justice organisation and urban farm working to stimulate local economic development, create jobs, and improve the quality and accessibility of food in Ashland and Cherryland in California's Bay Area. Their practices are based on self-determined values although they take a flexible, anti-essentialist approach to foodie logics, which are prominent and problematic in the Bay Area. The case study then examines specific practices and strategies, as well as intersections with foodie logics, in three arenas – values determination, strategic partnerships, and foodways – that help to cultivate food justice and highlights key characteristics of food justice work: emphasising self-determination and working to fundamentally change the economic and social conditions of food apartheid.     

Mixed models for assessing correlation in the presence of replication

The need to assess correlation in settings where multiple measurements are available on each of the variables of interest often arises in environmental science. However, this topic is not covered in introductory statistics texts. Although several ad hoc approaches can be used, they can easily lead to invalid conclusions and to a difficult choice of an appropriate measure of the correlation. Lam et al. approached this problem by using maximum likelihood estimation in cases where the replicate measurements are linked over time, but the method requires specialized software. We reanalyze the data of Lam et al. using PROC MIXED in SAS and show how to obtain the parameter estimates of interest with just a few lines of code. We then extend Lam et al.'s method to settings where the replicate measurements are not linked. Analysis of the unlinked case is illustrated with data from a study designed to assess correlations between indoor and outdoor measurements of benzene concentration in the air.     

Kin discrimination in the spotted hyena (<Emphasis Type="Italic">Crocuta crocuta</Emphasis>): nepotism among siblings

We examined patterns of affiliation, association, and aggression to inquire whether spotted hyenas (Crocuta crocuta) can distinguish among various groups of maternal and paternal siblings. If so, and if these animals conform to predictions of kin selection theory, then behavioral interactions among hyenas should vary with relatedness. We also considered familiarity-based recognition and phenotype matching as mechanisms hyenas might use to recognize kin. Patterns of affiliative behavior indicated that hyenas favored full-sibling littermates over half-sibling littermates or any other group of half-siblings. Rates of dyadic aggression generally did not vary with kinship. Hyenas associated more closely with half-sibling littermates than with non-littermate half-siblings, and hyenas affiliated more with maternal half-siblings than with paternal half-siblings, suggesting that familiarity-based cues might mediate discrimination among these sibling classes. In addition, operation of a phenotype-matching mechanism was suggested by the preference hyenas demonstrated during affiliative interactions for full- over half-sibling littermates, and by their lack of preference in these interactions for half-sibling littermates over non-littermate half-siblings. Phenotype matching was also suggested by our observation that paternal half-siblings cooperated more, and fought less, than did non-kin. Our data indicate that hyenas can discriminate among various types of siblings, that their social behavior conforms to predictions of kin selection theory, and that they recognize kin using mechanisms of both familiarity and phenotype matching.Communicated by S. Alberts     

What does it mean when climate models agree? A case for assessing independence among general circulation models

Climate modelers often use agreement among multiple general circulation models (GCMs) as a source of confidence in the accuracy of model projections. However, the significance of model agreement depends on how independent the models are from one another. The climate science literature does not address this. GCMs are independent of, and interdependent on one another, in different ways and degrees. Addressing the issue of model independence is crucial in explaining why agreement between models should boost confidence that their results have basis in reality.     

Should we be “challenging” employees?: A critical review and meta‐analysis of the challenge‐hindrance model of stress

The challenge‐hindrance model of stress proposes that stressors can be divided into two distinct groups: those that challenge employees and those that hinder employees. This critical review seeks to explain the history of the model and its basic tenets, while succinctly summarizing the findings of existing studies based on the model. A thorough search of the stress literature uncovered 32 studies that specifically examined the relationship between challenge and hindrance stressors and important personal/organizational variables. Results were reviewed and analyzed, specifically by describing past meta‐analyses on the model, looking at the overall pattern of results from primary studies, and meta‐analyzing the relationships presented in those papers. This synthesis suggests that although there are some differential relationships of challenge and hindrance stressors with organizational variables (e.g., performance and engagement), the relationships to other key variables, such as counterproductive work behaviors, psychological strains, and physical health, are consistently negative for both challenge and hindrance stressors. Thus, we propose that stress research move away from the current challenge‐hindrance model in favor of other established models and/or a more appraisal‐based approach.     

Farmers' Motivations for Adopting Conservation Practices along Riparian Zones in a Mid-western Agricultural Watershed

In the agricultural Mid-west, riparian corridors are vital for protecting biodiversity and water quality. The cumulative management decisions of hundreds of private landowners have a tremendous impact on this riparian zone. This study of 268 farmers in a typical Mid-western watershed in Michigan looked at farmer's motivations for adopting conservation practices, their current management practices along their rivers and drains as well as their future management plans. The results of the study showed that farmers are intrinsically motivated to practise conservation by such factors as their attachment to their land, rather than by motivations such as receiving economic compensation. Farmers are also likely to engage in conservation practices that make their farm appear well-managed. Furthermore, those farmers with strong intrinsic motivations were likely to adopt conservation practices that protect streams, such as maintaining a woody vegetative buffer or practicing no-till farming. This study shows that protecting riparian resources in agricultural watersheds requires strategies for conservation that respect farmers' attachment to their land and their desire to practise good stewardship.