On the Issue of Functional Form Choice in Hedonic Price Functions: Further Evidence

/ Historically, researchers applying the hedonic technique devoted little effort to testing alternative functional forms. This study used Box-Cox transformations on a hedonic model examining property value effects of a closed landfill to help select among alternative functional forms. Although this particular application found that a log-log functional form was appropriate, it appears that functional form may vary by problem and case study area selected. Benefit estimates generated using the hedonic technique may be substantial over- or underestimates if the incorrect functional form is chosen. Proximity to the landfill had no significant effect on property values.KEY WORDS: Hedonics; Functional form; Box-Cox; Landfills     

Performance of Greater Sage-Grouse Models for Conservation Assessment in the Interior Columbia Basin, U.S.A.

Abstract: Valid modeling of habitats and populations of Greater Sage-Grouse ( Centrocercus urophasianus) is a critical management need because of increasing concern about population viability. Consequently, we evaluated the performance of two models designed to assess landscape conditions for Greater Sage-Grouse across 13.6 million ha of sagebrush steppe in the interior Columbia Basin and adjacent portions of the Great Basin of the western United States (referred to as the basin). The first model, the environmental index model, predicted conditions at the scale of the subwatershed (mean size of approximately 7800 ha) based on inputs of habitat density, habitat quality, and effects of human disturbance. Predictions ranged on a continuous scale from 0 for lowest environmental index to 2 for optimal environmental index. The second model, the population outcome model, predicted the composite, range-wide conditions for sage grouse based on the contribution of environmental index values from all subwatersheds and measures of range extent and connectivity. Population outcomes were expressed as five classes (A through E) that represented a gradient from continuous, well-distributed populations (outcome A) to sparse, highly isolated populations with a high likelihood of extirpation (outcome E). To evaluate performance, we predicted environmental index values and population outcome classes in areas currently occupied by sage grouse versus areas where extirpation has occurred. Our a priori expectations were that models should predict substantially worse environmental conditions ( lower environmental index) and a substantially higher probability of extirpation ( lower population outcome class) in extirpated areas. Results for both models met these expectations. For example, a population outcome of class E was predicted for extirpated areas, as opposed to class C for occupied areas. These results suggest that our models provided reliable landscape predictions for the conditions tested. This finding is important for conservation planning in the basin, where the models were used to evaluate management of federal lands for sage grouse.     

Colony choice in birds: models based on temporally invariant site quality

We propose two stochastic models to explain how birds choose colonies. In the resource choice model, birds settle at each site at a rate proportional to the total resources the site contains. In the reduced resource choice model, a smaller cohort of birds enters sites at a rate determined by the total resources at each, and the remaining individuals enter sites at a rate that is linearly proportional to the total number of birds already nesting at each site. Thus, a fraction of birds chooses sites based on the resources present, and the remainder are attracted to a site by the presence of other birds. Colony site quality is assumed not to vary between years. Both models result, on average, in an ideal free distribution of colony sizes if the birds' settlement rate is linearly related to the resources in a site, if resources are distributed equally among individuals within sites, and if individuals with equal resources have equal fitness. We applied these models to long-term data on colony sizes and site usage of cliff swallows in south-western Nebraska. A test of the resource choice model suggested that the swallow population as a whole did not choose sites based strictly on site quality or the total resources contained at each site. However, a test of the reduced resource choice model suggested that a smaller fraction of the individuals in each colony may have based their choice of site on local resource availability, with the remaining birds aggregating at those sites based on the number of birds already settled there. Tests of these models may provide insight into how individuals choose colony sites and why colonies vary in size.     

Environmental response to intentional dissemination of Bacillus anthracis spores in the United States–2001

The intentional dissemination of Bacillus anthracis (anthrax) spores at multiple locations in the United States in the fall of 2001 resulted not only in several deaths and illnesses (including psychological effects), but likely changed lifestyles and attitudes, and increased the public's awareness of individual vulnerability. While federal resources had previously been committed to preparing local public health agencies for counter‐terrorism activities and to enhance environmental and medical response, these release episodes have increased the consistency of environmental and medical response activities, and increased government resources for homeland security. This article abstracts current information from many sources that summarize the environmental responses to the anthrax releases. The article discusses the international agreements and the U.S. regulations concerning biological weapons, the characteristics of the anthrax organism, potential exposure pathways, adverse health conditions resulting from inhalation exposure, the environmental response to two specific release episodes, environmental sampling and analytical procedures, recommended personal protective equipment, and the subsequent federal efforts to improve response capabilities. © 2003 Wiley Periodicals, Inc.     

Environmental and health impacts from the introduction of improved wood stoves: evidence from a field experiment in Guatemala

Improved wood-burning stoves offer a possible solution that can simultaneously impact both problems of deforestation and problems of respiratory health in developing countries. We carried out a field experiment in which new fuel-efficient woodstoves were allocated in a Guatemalan village via the use of a lottery. A 2008 baseline survey was carried out on 2,148 individuals in 351 households, and then a follow-up survey was carried out in 2009, 4 months after households received the stoves. We found that households with the new stoves reduced wood consumption by an average of 59.1%. We also found indications of reductions in indoor air related health problems, where point estimates indicate a significant reduction in reported respiratory symptoms by 48.6% among women and 63.3% among children.     

Addressing identity-related barriers to collaboration for conservation through self-affirmation theory and moral foundations theory

The natural resource management literature documents many reasons for pursuing collaborative processes, offering useful insights on how to manage conflict and facilitate productive deliberation in complex multistakeholder collaborative efforts. Moral foundations theory and self-affirmation theory can further help collaborative efforts mitigate conflicts caused by identity threats and the identity-protective reasoning these threats provoke. Moral foundations theory suggests an approach to increase collaboration by minimizing triggering language and helping people appreciate opposing viewpoints. Self-affirmation theory suggests a practical intervention that could be used to increase collaboration by desensitizing people to identity threats and reducing defensiveness. Taken together, these theories can contribute substantially to the understanding and practice of collaboration and conflict management for conservation.     

沉积物毒性鉴别评估技术在一个有着多重污染物输入地点的应用

沉积物毒性鉴别评估用于确定造成沉积物整体毒性测试中观察到有害效果的原因。然而在多污染物的情况下,将总体毒性划分为为不同个体污染物单独造成的毒性的方法存在很多问题。利用一个有着多重输入与相关污染物的站点数据,我们为毒性鉴别评估提出一种通过追踪毒性单位（TUs）来确定是否囊括全部毒性的方法。首先确定出沉积物整体的毒性水平,然后将毒性来源划分至几种污染物大类,例如氨类,金属,非极性有机物等。本文中毒性很大程度上来源于非极性有机物,所以在萃取沉积物之后,将萃取物重新加回稀释水中以检测毒性的复原。每一部分污染物的毒性占比由溶剂梯度测量,并进行毒性检测。目标占比由气相色谱-质谱分析得到,从而鉴定出与特定成分相关的毒性。之后对这些成分相关的毒性单位进行测定以确定可能的原因组合和是否已囊括全部毒性。数据表明毒性既与已有化合物相关,又与新兴污染物相关,而两种污染物对于总体毒性的具体贡献则随实验地点改变。
精选自Howard C. Bailey, Catherine A. Curran, Peter Arth, Bonnie P. Lo, Rich Gossett. Application of Sediment Toxicity Identification Evaluation Techniques to a Site with Multiple-Contaminants. Environmental Toxicology and Chemistry: Volume 35, Issue 10, pages 2456–2465, October 2016. DOI: 10.1002/etc.3488
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.3488/full