Implications of simultaneity in a physical damage function

A modeler must often rely on highly simplified representations of complex physical systems when analyzing associated economic issues. Herein, we consider a management problem in which a bioeconomic system exhibits simultaneity in processes governing productivity and damage. In this case, it may benefit the producer to sacrifice productivity to reduce the costs associated with increased damage. We specify empirically a structural damage relationship that explains the biological process by which an invasive species damages a host and estimate the structural model and its reduced form with an exceptional dataset on infestation of olives by the olive fruit fly. We contrast the results of these models with the approach typically taken in the economic literature, which expresses damage as a function of pest density. The population-based approach introduces significantly greater bias into the individual grower's choice of damage-control inputs than estimates based on the structural model.     

Regional extinction of a conspicuous dorid nudibranch (Mollusca: Gastropoda) in California

Felimare californiensis (=Hypselodoris californiensis) was once common throughout the Southern California Bight (SCB) and California Channel Islands. This well-known shallow-water nudibranch, which specializes on dysideid sponges, has persisted for decades in Mexico, but in California disappeared from its entire range by 1984. Since reappearing in 2003, it has been found only at Santa Catalina Island, plus sightings of single individuals in 2011 at Santa Cruz Island and San Diego. The decline of F. californiensis in California was documented using published historical records, museum collections, unpublished field accounts, and images posted online. The loss of this emblematic species is unique among Californian nudibranchs, including (1) its congener Felimare porterae (=Mexichromis porterae), with which it appears to overlap in diet, and (2) opisthobranch species with similar historical geographic ranges and mode of development. The decline in F. californiensis is not predicted by warming trends and climate variation over the past 40 years, including the strong El Niño events of 1983 and 1998. Coastal pollution from the large human population in southern California may have impacted Dysidea amblia, the primary reported prey of F. californiensis. Historical overcollecting of the nudibranch and habitat loss through the development of major ports likely also contributed to its decline. Sightings since 2003 are consistent with a nascent recovery, as elements of water quality have improved in the SCB in recent decades.     

DOWNSTREAM CHANNEL GEOMETRY FOR USE IN PLANNING-LEVEL MODELS1

ABSTRACT: There is considerable potential for use of channel dimension data in planning-level models for resource and impact assessment. The channel dimension data is used to route flows and sediment through the basin. The cost of obtaining actual surveyed data for large watersheds is typically prohibitive. Predictive equations have been developed based on 674 stations from watersheds across the United States which encompass a wide variety of channel types and sizes. These equations were tested against an independent data set and found to be adequate for use in planning-level models. Future research is advocated which would include data from regions and stream types not included in this study.     

Liquid household hazardous wastes in the United States: Identification,disposal, and management plan

Present methods of disposal of today's hazardous household chemicals in the United States are frequently not acceptable because of pathways to groundwater, surface water, and the atmosphere. This report identifies potentially hazardous liquid waste in the household, notes current disposal practices, and recommends an improved management plan that utilizes consumer education, manufacturer cooperation, and governmental intervention. Laws requiring uniform disposal labeling on packaging are critical. Local, county, and state governments must be encouraged to coordinate the necessary infrastructure. Managing hazardous household wastes now will mitigate potential disposal problems.     

Management practices that concentrate visitor activities: camping impact management at Isle Royale National Park,USA

This study assessed campsite conditions and the effectiveness of campsite impact management strategies at Isle Royale National Park, USA. Protocols for assessing indicators of vegetation and soil conditions were developed and applied to 156 campsites and 88 shelters within 36 backcountry campgrounds. The average site was 68 m2 and 83% of sites lost vegetation over areas less than 47 m2. We believe that management actions implemented to spatially concentrate camping activities and reduce camping disturbance have been highly successful. Comparisons of disturbed area/overnight stay among other protected areas reinforces this assertion. These reductions in area of camping disturbance are attributed to a designated site camping policy, limitation on site numbers, construction of sites in sloping terrain, use of facilities, and an ongoing program of campsite maintenance. Such actions are most appropriate in higher use backcountry and wilderness settings.     

ERODIBILITY OF URBAN BEDROCK AND ALLUVIAL CHANNELS,NORTH TEXAS1

ABSTRACT: Major erosion of urban stream channels is found in smaller basins in the North Texas study area with contributing drainage areas of less than ten square miles. Within these basins, four basic channel types are identified based on bed and bank lithologies: alluvial banks and bottoms, alluvial banks and gravel bottoms, alluvial banks with rock bottoms, and rock banks with rock bottoms. Most channels (75 percent) have alluvial banks with gravel or rock bottoms. Channel slopes are steep (.38 to.76 percent). Rock consists predominantly of shale and limestone. Channel cross sections are divided into the following four zones based on weathering, scour and entrainment mechanisms: soil zone, slake zone, rock zone and bed material zone. Erodibility of the channels is determined using multiple techniques including reach hydraulics and stream power computations, submerged jet testing, slab entrainment thresholds, and slake durability rates. Procedures are based on both empirical and modeled time series estimates of channel erosion. Field and modeled results support rates of erosion of up to four inches per year. Rates are tied to flow regime, climate, and type of channel bed and banks.     

ADJUSTMENT OF STREAM CHANNEL CAPACITY FOLLOWING DAM CLOSURE,YEGUA CREEK,TEXAS1

ABSTRACT: In Yegua Creek, a principal tributary of the Brazos River in Texas, surveys of a 19 km channel reach downstream of Somerville Dam show that channel capacity decreased by an average of 65 percent in a 34 year period following dam closure. The decrease corresponds with an approximately 85 percent reduction in annual flood peaks. Channel depth has changed the most, decreasing by an average of 61 percent. Channel width remained stable with an average decrease of only 9 percent, reflecting cohesive bank materials along with the growth of riparian vegetation resulting from increased low flows during dry summer months. Although large changes in stream channel geometry are not uncommon downstream of dams, such pronounced reductions in channel capacity could have long‐term implications for sediment delivery through the system.     

Evaluating regulatory issues and emission control equipment for air toxics applications

This article describes regulatory issues and emission control equipment for air toxics applications. A brief history of air quality legislation is provided, illustrating the difficulty government has had in implementing air quality statutes; this has contributed to the complexity of air quality regulations. Evaluation methodologies are described for three different emission control technologies: thermal oxidation, catalytic oxidation, and adsorption. Brief case histories are provided that describe the pitfalls and benefits associated with each technology. The benefits of integrating health risk assessment into an air quality program are also discussed.     

The team solution for effective project management

In their new book The TeamNet Factor: Bringing the Power of Boundary Crossing into the Heart of Your Business, authors Jessica Lipnack and Jeffrey Stamps claim that businesses that form teamnets—networks of teams that cross conventional boundaries—will be winners in the twenty-first century global economy. From the smallest to the largest companies, businesses are climbing over their own walls. Customers, competitors, and even people in different industries traverse their traditional limits to work together. When business teams cross boundaries, benefits accrue. Whether three-person shops or multinationals, these companies can achieve something that by themselves would be impossible. By definition, teamnets are on a mission for mutual benefit. Large firms in many industries are using internal teamnets to bridge barriers inside their companies and external teamnets to bridge boundaries with suppliers, customers, and competitors. The following excerpt presents insightful ideas and techniques for quality professionals on how to implement more effective project management through teams.