bluuebunny/crossref_metadata_2025 huggingface dataset:
The Socioeconomic Attainment Patterns of Africans in the United States
Authors: Kollehlon Konia T. , Eule Edward E.
Published: August 2010

Using data from the public use microdata sample of the 1990 U.S. census, we examine the socioeconomic attainment patterns of Africans in the United States, within the context of the assimilation and selectivity perspectives. Three primary findings emerge from this study. First, we find that white African men and men from English-speaking Africa have higher net hourly earnings than their nonwhite and non-English-speaking counterparts. Second, we find that while South African men have higher net hourly earnings than men from a number of selected African countries, there is no statistically significant difference between the net hourly earnings of South African women and women from these selected African countries. Third, we find no statistically significant difference between the net hourly earnings of black African and black American men and women.
Gendering Interprovincial Migration in China
Authors: He Canfei , Gober Patricia
Published: August 2010

Migration is a gendered phenomenon, best understood as a series of relationships between socioeconomic factors and gender. Gender differences in migration efficiencies are investigated using the 1990 Census data in China. Results indicate that, although male migration rates are higher, female migration is more efficient in the sense that it contributes to greater population redistribution than male migration. Reflecting different economic and social roles, women are more likely to state social and family reasons for moving while men indicate economic motivations. In terms of the geography of movement, women are more sensitive than men to perceived and expected regional differences in economic opportunities, especially in rural areas. Job opportunities created in urban areas and by foreign enterprises are more attractive to male migrants. Development of light manufacturing industries and the benefits derived from the presence of previous migrants draw female more than male migrants.
AgJOBS: New Solution or New Problem?
Authors: Martin Philip
Published: August 2010

Over half of the workers employed on U.S. farms are not authorized to work in the United States. An historic compromise between employer and worker advocates in September 2003 would legalize some currently unauthorized workers and make it easier for farmers to obtain guest workers, but is unlikely to change the farm labor market, so that the percentage of unauthorized workers is likely to climb again.
The More Things Change the More They Stay the Same: Mexican Naturalization before and after Welfare Reform
Authors: Balistreri Kelly Stamper , Van Hook Jennifer
Published: August 2010

During the last decade there has been a dramatic increase in the both the number and the rate of Mexican naturalization. Some have interpreted this increase as a response to changes in welfare and immigration policy surrounding the 1996 Personal Responsibility and Work Opportunity Reconciliation Act (PRWORA), which limited public assistance to non-citizens, and the 1996 Illegal Immigration Reform and Immigrant Responsibility Act (IIRIRA), which may have increased the incentive to naturalize by making it more difficult for legal immigrants to sponsor their relatives for entry to the United States. This article uses Current Population Survey data from 1994/95 and 2000/01 to examine how the social and economic determinants of naturalization may have changed in order to provide insight into which explanation for the increase in naturalizations is most relevant. We find that while the proportion of Mexican immigrants who are naturalized increased during the 1990s, their determinants have remained largely the same with the exception that those with noncitizen spouses have become more likely to be naturalized in the post-reform period. This suggests that a more cautious interpretation be taken about the relationship between the increase in naturalizations and welfare and sponsorship restrictions, particularly when regarding Mexican immigrants.
Afro-Caribbeans and Indo-Caribbeans in the Netherlands: Premigration Legacies and Social Mobility
Authors: van Niekerk Mies
Published: August 2010

The social mobility of immigrants depends not just on the opportunity structure of the receiving society, but also on the past experiences and the sociocultural repertoires that immigrants bring with them on arrival. This becomes clear in a comparison of two ethnic groups that migrated from one Caribbean country to the Netherlands: the Afro-Surinamese and Indo-Surinamese. While both groups left Surinam at the same time and settled into very similar conditions in the Netherlands, their premigration histories differed considerably. These different premigration legacies seem crucial to understanding the current differences in the economic and educational performance of these immigrants and their offspring.
The Factors that Make and Unmake Migration Policies
Authors: Castles Stephen
Published: August 2010

Migration policies often fail to achieve their declared objectives or have unintended consequences. This article discusses three sets of reasons for this: factors arising from the social dynamics of the migratory process; factors linked to globalization and transnationalism; and factors within political systems. Effective policies are often hampered by the one-sided explanatory models used to explain migration, as well as by interest conflicts in both domestic and international politics. In many cases this leads to migration policies with contradictory objectives or hidden agendas. The article goes on to discuss some elements of a conceptual framework for improving policy formation and possible components of fairer and more effective migration policies at the national, regional and global levels.
Dual Citizenship as a Path-Dependent Process
Authors: Faist Thomas , Gerdes Jürgen , Rieple Beate
Published: August 2010

Over the last few decades, dual nationalities worldwide have increased rapidly. This is astonishing when one considers that a few decades ago citizenship and political loyalty to a national political community were considered inseparable. Overall, there has been a bumpy-line trend towards increasing tolerance. Yet, the degree to which dual nationality is tolerated by states differs. Based on the findings of postnational and national perspectives, this analysis proposes to view tolerance and resistance towards dual nationality as a path-dependent process. The questions dealt with are: What are the factors encouraging the generally increasing tolerance towards multiple nationalities? How can cross-national differences regarding de jure and de facto tolerance towards dual nationality be explained? The main tendency over the past decades has been the growing emphasis on individual rights vis-à-vis state prerogatives in liberal democracies. The expansion of de jure tolerance towards dual nationality is due partly to inter-, supra- and national-level developments, which are connected to diverse factors such as gender equity, understandings of nationhood, immigrant incorporation and general characteristics of the political systems.
Arab Migration to Europe: Trends and Policies
Authors: Fargues Philippe
Published: August 2010

Growing Arab migration to Europe is a likely scenario for the coming years, poorly prepared for by current policies. The paper examines three reasons for this scenario: new patterns of family-building in Arab countries; aging in Europe; and the emergence of a new demand for migrant labor. While the ongoing establishment of free trade may increase migratory pressures, government policies remain potentially conflicting –on the Arab side, optimizing the economic benefits drawn from emigrants and reviving their sense of belonging to their culture of origin; on the European side, restricting further immigration and integrating former migrants in the host society and culture.
Albanian and Polish Migration to Italy: The Micro-Processes of Policy, Implementation and Immigrant Survival Strategies
Authors: Kosic Ankica , Triandafyllidou Anna
Published: August 2010

This article examines how undocumented immigrants take advantage or react to the windows of opportunity opened to them by immigration policy design and implementation practices in the country of destination. The study concentrates on the case of Albanian and Polish immigrants in Italy. Looking into the policy provisions regarding entry, stay and immigrant employment in Italy, as well as the practices of implementation adopted by the public administration, we study how immigrants prepare and execute their migration plans, how they find employment once in Italy, and how they adapt their plans to the institutional and social environments of the host country as well as their own wishes and needs. We thus highlight the micro-level of the migration phenomenon and the dynamic relationship between policy design, implementation and immigrant strategies.
Transnational Twist: Pecuniary Remittances and the Socioeconomic Integration of Authorized and Unauthorized Mexican Immigrants in Los Angeles County
Authors: Marcelli Enrico A. , Lowell B. Lindsay
Published: August 2010

Annual U.S.-Mexico pecuniary remittances are estimated to have more than doubled recently to at least $10 billion – augmenting interest among policymakers, financial institutions, and transnational migrant communities concerning how relatively poor expatriate Mexicans sustain such large transfers and the impact on immigrant integration in the United States. We employ the 2001 Los Angeles County Mexican Immigrant Residency Status Survey (LAC-MIRSS) to investigate how individual characteristics and social capital traditionally associated with integration, neighborhood context, and various investments in the United States influenced remitting in 2000. Remitting is estimated to have been inversely related to conventional integration metrics and influenced by community context in both sending and receiving areas. Contrary to straight-line assimilation theories and more consistent with a transnational or nonlinear perspective, however, remittances are also estimated to have been positively related to immigrant homeownership in Los Angeles County and negatively associated with having had public health insurance such as Medicaid.
Will They Ever Converge? Earnings of Immigrant and Canadian-born Workers over the Last Two Decades
Authors: Frenette Marc , Morissette René
Published: August 2010

Using Census data covering the 1980–2000 period, this article examines what outcomes would be necessary for today's recent immigrant cohorts to achieve earnings parity with Canadian-born workers. Our results show that today's recent immigrants would have to experience a drastic steepening of their relative age-earnings profile in the near future for their earnings to converge with their Canadian-born counterparts. The reason is simple: the greater relative earnings growth experienced by recent immigrant cohorts has only partially offset the drastic deterioration in their relative earnings at entry.
WELFARE MEASUREMENT AND COST‐BENEFIT ANALYSIS IN NASH AND STACKELBERG DIFFERENTIAL FISH GAMES
Authors: LOFGREN KARL‐GUSTAF
Published: August 2010

ABSTRACT.This paper develops welfare measures and cost‐benefit rules in Nash and Stackelberg differential fish games. The model consists of two fisheries competing on a common fishing ground, but the results are valid in more general settings. Under steady state conditions, the present value of the fisheries' future profit is directly proportional to the current profit plus the value of the net investments in the fish population (the Hamiltonian). Outside the steady state, the rule must, under a Nash game, be modified by adding the present value of the marginal harm done to the fishery by the competitor's future catches to the Hamiltonian. Under a Stackelberg game the present value of the leader's future profit remains proportional to the value of his Hamiltonian.
LOCATIONAL EQUILIBRIUM MODELS FOR PUBLICLY OWNED RESIDENTIAL LAND
Authors: WAN FREDERIC Y.M.
Published: August 2010

ABSTRACT. Perturbation and matched asymptotic expansion methods are shown to be useful to the study of land economics. In the context of residential land management theory, the present study complements a previous analysis of locational equilibrium economic models for residential land in Wan [1977] and extends it beyond absentee ownership to include public ownership and mixed ownership. The dependence of the optimal uniform household utility on the (radial) distribution of land fraction for housing space is delineated.
ASYMPTOTIC METHODS: APPLICATION TO REDUCTION OF MODELS
Authors: KALACHEV LEONID V.
Published: August 2010

ABSTRACT. A survey of results on reduction of models related to problems of natural resource modeling using the boundary function method is presented. Detailed reduction procedures as well as conditions under which the reductions are at all possible are discussed. Particular asymptotic techniques are illustrated by simple examples taken from chemical kinetics, and a realistic example from atmospheric chemistry modeling.
MONOPOLY, POTENTIAL COMPETITION AND PRIVATE STOCK INFORMATION IN EXHAUSTIBLE RESOURCE MARKETS
Authors: AGEE MARK D.
Published: August 2010

ABSTRACT. This paper develops an exhaustible resource model with an incumbent monopolist that faces future potential entry of a single rival or backstop technology. The model is characterized by private stock information in the sense that firms do not know with certainty the size and/or quality of their rival's reserve stock. Results indicate that if such information is private, the strategic response of the monopolist to an entry threat is to extract reserves in the pre‐entry era at a rate faster than would a pure monopolist in an uncontested market, and thus could lead to an improvement in economic welfare relative to the situation where entry is restricted.
A NUMERICAL STUDY OF THE SPRUCE BUDWORM REACTION‐DIFFUSION EQUATION WITH HOSTILE BOUNDARIES
Authors: SINGH MANMOHAN , EASTON ALAN , KOZLOVA IRINA
Published: August 2010

ABSTRACT. One of the interesting single species reaction diffusion problems is the spruce budworm model describing insect dispersal behavior. In an earlier study, Singh et al. [7] considered the two‐dimensional spruce budworm model with density dependent diffusion balanced by an artificial wind equal to the population gradient. Here we extend the model by considering more realistic density dependent diffusion and advection with hostile boundaries. We solve this model using a splitting method in which advection, diffusion and reaction processes are separated. Various hostility conditions have been used at the boundary. The numerical results show that the population moves quickly to a steady state outbreak situation when the advective components due to the density dependent diffusion are included.
ON OPTIMAL ENVIRONMENTAL TAXATION AND ENFORCEMENT: INFORMATION, MONITORING AND EFFICIENCY
Authors: GÓMEZ CARLOS MARIO GÓMEZ
Published: August 2010

ABSTRACT. The purpose of the paper is to contribute to the narrowing of the distance between formal theory and practical environmental policy design. We formulate a general and comprehensive theoretical model in order to take into account the different informational and technological problems which characterize the definition and implementation of environmental taxes in a second best world where there also are distortionary taxes. Having formalized these problems, we present a general model which allows us to discuss the existence of efficient and implementable environmental quality objectives and policy instruments, and to analyze many particular cases.
INCORPORATION AND INFLUENCE OF VARIABILITY IN AN AGGREGATED FOREST MODEL
Authors: LÖFFLER T.J. , LISCHKE H.
Published: August 2010

ABSTRACT. Variability influences ecological processes at various scales and is incorporated in different ways in forest models. The forest model DisCForM scales an individual based, stochastic forest patch model up to a height structured tree population model. To describe the variability arising from stochastic processes in the patch model, DisCForM uses theoretical random dispersions of trees in each height class over all patches. This yields a spatial distribution of light and consequently of light dependent process rates. Three major influences of variability on simulations are examined: site condition, patch to patch, and temporal environmental variability. Simulation studies and comparison with forest compositions from the Swiss National Forest Inventory reveal that these influences affect simulated forest dynamics, species composition, and biodiversity, depending on climatic boundary conditions and hence have to be taken into account in modeling.
SPATIAL PATTERN INDUCED BY ASYMMETRIC COMPETITION: A MODELING APPROACH
Authors: PICARD NICOLAS , BAR‐HEN AVNER , ENGREF ALAIN FRANC
Published: August 2010

ABSTRACT. The paper addresses the question: how does asymmetric competition for light affect the spatial pattern of trees? It is based on an individual‐based spatially explicit model of forest dynamics, whose growth equations are derived from gap models. The model is calibrated on a stand of natural rainforest in French Guiana, where the tree pattern exhibits regularity at short distances (< 10 m) and clustering at medium distances (∼ 30 m). The model reproduces the regularity but not the clustering. As mortality and recruitment have been modeled so as to favor a random pattern, we conclude that regularity emerges from the asymmetric competition in the growth submodel. Also the scale at which regularity appears is linked to the range of interactions between trees.
POPULATION BIOLOGY AND ECOLOGY OF THE SOLE
Authors: HORWOOD JOSEPH
Published: August 2010

ABSTRACT. The sole (Solea solea) is a typical temperate marine flatfish. Population numbers have been significantly reduced, by fishing, before biological sampling was routinely established. There is thus an inadequate description of the demographic processes with changing population density. Nevertheless, it is possible to see some changes in weight, maturity and fecundity of adult sole, although these may well be driven by environmental factors. Sole aggregate in shallow‐water nursery grounds, where there is probably density‐dependent mortality, and a hypothesis that the size of nursery grounds controls average population size is examined. It is argued, however, that the important homeostatic process occurs in the plankton. The dynamics of the sole can then only be understood in the context of the plankton ecology.
EFFECTS OF DOMAIN SIZE ON THE PERSISTENCE OF POPULATIONS IN A DIFFUSIVE FOOD‐CHAIN MODEL WITH BEDDINGTON‐DeANGELIS FUNCTIONAL RESPONSE
Authors: CANTRELL ROBERT STEPHEN , COSNER CHRIS
Published: August 2010

ABSTRACT. A food chain consisting of species at three trophic levels is modeled using Beddington‐DeAngelis functional responses as the links between trophic levels. The dispersal of the species is modeled by diffusion, so the resulting model is a three component reaction‐diffusion system. The behavior of the system is described in terms of predictions of extinction or persistence of the species. Persistence is characterized via permanence, i.e., uniform persistence plus dissi‐pativity. The way that the predictions of extinction or persistence depend on domain size is studied by examining how they vary as the size (but not the shape) of the underlying spatial domain is changed.
SCALE AND EQUITY IN WATER RESOURCE DEVELOPMENT: A NASH BARGAINING MODEL
Authors: DINAR ARIEL
Published: August 2010

ABSTRACT. This paper presents an application of the Nash model to a combined problem of optimal development of a joint facility and related cost‐benefit allocation considerations. Two alternative modifications and a diagrammatic procedure are developed. The conditions for an optimal Nash solution are derived. The procedure is illustrated using an example from a regional water development project that includes determination of the optimal capacity and allocation of costs and water among participants.
SPOTTED OWL PROTECTION, BOOMING HOUSING MARKET, AND LOG PRICE CHANGES IN THE PACIFIC NORTHWEST
Authors: YIN RUNSHENG
Published: August 2010

ABSTRACT. In this paper we assess the impacts of the federal policy shifts and the booming housing market on log price changes in the Pacific Northwest. Our intervention analysis and causality test indicate that both factors have affected the log market dynamics. Our further estimation shows that at least 71% of the log price movements might have been caused by the policy shifts induced by the spotted owl debate, with the remaining caused by lumber price changes driven by the booming housing market. We also discuss the implications of our results for understanding policy decision and market behavior.
TOWARDS A STANDARD FOR THE INDIVIDUAL‐BASED MODELING OF PLANT POPULATIONS: SELF‐THINNING AND THE FIELD‐OF‐NEIGHBORHOOD APPROACH
Authors: BERGER UTA , HILDENBRANDT HANNO , GRIMM VOLKER
Published: August 2010

ABSTRACT.In classical theoretical ecology there are numerous standard models which are simple, generally applicable, and have well‐known properties. These standard models are widely used as building blocks for all kinds of theoretical and applied models. In contrast, there is a total lack of standard individual‐based models (IBM's), even though they are badly needed if the advantages of the individual‐based approach are to be exploited more efficiently. We discuss the recently developed ‘field‐of‐neighborhood’ approach as a possible standard for modeling plant populations. In this approach, a plant is characterized by a circular zone of influence that grows with the plant, and a field of neighborhood that for each point within the zone of influence describes the strength of competition, i.e., growth reduction, on neighboring plants. Local competition is thus described phenomenologically. We show that a model of mangrove forest dynamics, KiWi, which is based on the FON approach, is capable of reproducing self‐thinning trajectories in an almost textbook‐like manner. In addition, we show that the entire biomass‐density trajectory (bdt) can be divided into four sections which are related to the skewness of the stem diameter distributions of the cohort. The skewness shows two zero crossings during the complete development of the population. These zero crossings indicate the beginning and the end of the self‐thinning process. A characteristic decay of the positive skewness accompanies the occurrence of a linearbdtsection, the well‐known self‐thinning line. Although the slope of this line is not fixed, it is confined in two directions, with morphological constraints determining the lower limit and the strength of neighborhood competition exerted by the individuals marking the upper limit.
MODELING THE MOVEMENTS OF COWBIRDS: APPLICATION TOWARDS MANAGEMENT AT THE LANDSCAPE SCALE
Authors: HARPER STEVEN J. , WESTERVELT JAMES D. , SHAPIRO ANN‐MARIE
Published: August 2010

ABSTRACT. Brood parasitism by brown‐headed cowbirds (Molothrus ater) reduces the reproductive success of two endangered bird species at Fort Hood, Texas. A successful management program has focused on trapping cowbirds at feeding locations, grassland areas almost always associated with the presence of cattle. To enhance the efficacy of this effort, we developed an individual‐based model that predicted visitation rates by cowbirds to all potential feeding locations at Fort Hood and the surrounding landscape. Utilizing GRASS‐GIS and SWARM, the model incorporated the spatial arrangement of habitats, daily movements of cattle, and daily movements of cowbirds from their breeding sites to feeding locations. We simulated four types of movements by cow‐birds as they searched for cattle: 1) random walk, 2) direct return to previous locations (i.e., memory), 3) return to previous locations with en route assessment (i.e., memory with limited perception of the current state of the system), and 4) omniscience. Straight‐line distances between breeding and feeding locations for cowbirds that used the memory‐with‐perception rule were similar to independent telemetry results, and total search distances for this movement type approached those of omniscience. Both movement distance measures were inversely related to perception distance. Maps of cowbird visits to feeding areas differed among movement rules but were not strongly affected by the density of breeding cow‐birds. Maps also identified locations where trapping efforts could reduce parasitism within specific areas known to support endangered species. While it seems plausible that cowbirds are able to remember foraging locations and to perceive their surroundings as they travel, additional studies are needed to document their cognitive abilities. By simulating movements of individual cowbirds across a dynamic landscape, model results may help to strengthen ongoing cowbird control efforts.
A CLASS OF MODELS DESCRIBING AGE STRUCTURE DYNAMICS IN A NATURAL FOREST
Authors: KRAEMER MICHAEL A. , KALACHEV LEONID V. , COBLE DEAN W.
Published: August 2010

ABSTRACT.The age dynamics of a natural forest is modeled by the von‐Foerster partial differential equation for the age density, while the seedling density is obtained as a solution of an integro‐differential equation. This seedling density equation contains a small parameter, the ratio of seedling re‐establishment time and the life span of an average tree in the forest. Several models are introduced that take into account various mortality curves and growth functions of trees, the dependence of seedlings carrying capacity on forest size, and different types of seedlings re‐establishment. Asymptotic, analytic and numerical methods are used to solve typical example problems.
A TWO‐STAGE INFORMATION‐THEORETIC APPROACH TO MODELING LANDSCAPE‐LEVEL ATTRIBUTES AND MAXIMUM RECRUITMENT OF CHINOOK SALMON IN THE COLUMBIA RIVER BASIN
Authors: THOMPSON WILLIAM L. , LEE DANNY C.
Published: August 2010

ABSTRACT. Many anadromous salmonid stocks in the Pacific Northwest are at their lowest recorded levels, which has raised questions regarding their long‐term persistence under current conditions. There are a number of factors, such as freshwater spawning and rearing habitat, that could potentially influence their numbers. Therefore, we used the latest advances in information‐theoretic methods in a two‐stage modeling process to investigate relationships between landscape‐level habitat attributes and maximum recruitment of 25 index stocks of chinook salmon (Onocorhynchus tshawy‐tscha) in the Columbia River basin. Our first‐stage model selection results indicated that the Ricker‐type, stock recruitment model with a constant Ricker a, i.e., recruits‐per‐spawner at low numbers of fish) across stocks was the only plausible one given these data, which contrasted with previous unpublished findings. Our second‐stage results revealed that maximum recruitment of chinook salmon had a strongly negative relationship with percentage of surrounding subwatersheds categorized as predominantly containing U.S.

Forest Service and private moderate‐high impact managed forest. That is, our model predicted that average maximum recruitment of chinook salmon would decrease by at least 247 fish for every increase of 33% in surrounding subwatersheds categorized as predominantly containing U.S. Forest Service and privately managed forest. Conversely, mean annual air temperature had a positive relationship with salmon maximum recruitment, with an average increase of at least 179 fish for every increase in 2°C mean annual air temperature.
THE IMPACTS OF MARINE RESERVES ON LIMITED‐ENTRY FISHERIES
Authors: SANCHIRICO JAMES N. , WILEN JAMES E.
Published: August 2010

ABSTRACT. We utilize a spatial bioeconomic model to investigate the impacts of creating reserves on limited‐entry fisheries. We find that reserve creation can produce win‐win situations where aggregate biomass and the common license (lease) price increase. These situations arise in biological systems where dispersal processes are prevalent and the fishery prior to reserve creation is operating at effort levels in a neighborhood of open‐access levels. We also illustrate that using strictly biological criteria for siting reserves (e.g., setting aside the most biological productive areas) will likely induce the most vociferous objections from the fishing industry. In general, we find that the dispersal rate and the degree the patches are connected play a significant role on the net impacts on the fishing sector.
FISHERY BENEFITS OF FULLY PROTECTED MARINE RESERVES: WHY HABITAT AND BEHAVIOR ARE IMPORTANT
Authors: ROBERTS CALLUM M. , SARGANT HELEN
Published: August 2010

ABSTRACT. Fully protected marine reserves, areas that are closed to all fishing, have attracted great interest for their potential to benefit fisheries. A wide range of models suggest reserves will be most effective for species that are relatively sedentary as adults but produce offspring that disperse widely. Adult spawning stocks will be secure from capture in reserves, while their offspring disperse freely into fishing grounds. Such species include animals like reef fish, mollusks and echino‐derms, and models typically indicate that when they are over‐fished, catches will be higher with reserves than without. By contrast, the same models suggest that reserves will be ineffective for animals that are mobile as adults species like cod, tuna or sharks. They remain vulnerable to fishing whenever they move outside reserves. Unfortunately, most models lack sufficient realism to effectively gauge reserve effects on migratory species. They usually assume that individuals are homogeneously distributed in a uniform sea and move randomly. They also assume that fishers hunt at random. Neither is true. For centuries, fishers have targeted places and times when their quarry are most vulnerable to capture. Protecting these sites could have disproportionately large effects on stocks. Furthermore, models rarely take into account possible benefits from improvements in habitat within reserves. Such changes, like increased biomass and complexity of bottom‐living organisms, could alter fish movement patterns and reduce natural mortality rates in ways that enhance reserve benefits. We present a simple model of reserve effects on a migratory fish species. The model incorporates spatial variation in vulnerability to capture and shows that strategically placed reserves can offer benefits in the form of increased spawning stock and catch, especially when fishing intensities are high. We need to develop a new generation of models that incorporate habitat and behaviour to better explore the utility of reserves for mobile species. Migratory behavior does not preclude reserves from benefiting a species, but it demands that we apply different principles in designing them. We must identify critical sites to species and develop reserve networks that focus protection on those places.
THE EFFECT OF INFORMATION ON A STOCHASTIC, SPATIALLY DISTRIBUTED FISHERY
Authors: CRIPE GREG
Published: August 2010

ABSTRACT. Survival rates and carrying capacities in a fishery may be strongly affected by variations in climatic factors. When the stock is under the control of a single manager, information about the stochastic growth parameters leads to improved economic returns. However, when the stock is transboundary, additional information concerning the stochastic parameters can lead to over harvesting and in turn to lower economic returns. When the harvests are taken sequentially by more than one fleet, additional information will benefit the first harvester while harming those who follow.
DESIGNING FISHERY MODELS: A PERSONAL ADVENTURE
Authors: SCHNUTE JON T.
Published: August 2010

ABSTRACT. This paper describes my experiences designing fishery models, starting from a mathematical background in the differential equations of theoretical physics. Three examples from my early research, cited by Quinn in the lead article for this issue, illustrate a historical approach to model design. Although such analytical results provide useful tools for thought, they sometimes gloss over important assumptions and limitations. I describe the series of questions that led me from simple models to a more complete statistical framework, involving state space models and Bayes statistics. Modern fishery models often grow into complex structures that depend on numerous arbitrary choices about underlying deterministic processes, process error, and measurement error. Given this inherent ambiguity and uncertainty, I discuss scientific limits to quantitative fishery models and future prospects for devising robust management algorithms.
FROM THE GOLDEN AGE TO THE NEW INDUSTRIAL AGE: FISHERY MODELING IN THE EARLY 21ST CENTURY
Authors: PRAGER MICHAEL H. , WILLIAMS ERIK H.
Published: August 2010

ABSTRACT. If the Golden Age of fishery modeling is over, the New Industrial Age is beginning. In this new age (the early decades of the 21st century), we1 expect to see increasing use of high‐level modeling tools, assessments closely tailored to each stock and its data, more multi‐agency collaboration, wider use of multiple‐model assessments, and extensive peer review of stock assessments. We hope that fishery management, as well, will be seen as a proper object of peer review, from which it should benefit substantially. We believe that increasing attention will be paid to financial efficiency, both in shaping data collection programs and in specifying what information must be modeled to effect management. If presently depleted stocks start to recover, analysts will be required to examine in more detail the dynamics of increasing stocks. That would constitute a pleasant duty, and one that may yield new insights in population biology.
FOREST ROTATIONS AND STAND INTERDEPENDENCY: OWNERSHIP STRUCTURE AND TIMING OF DECISIONS
Authors: AMACHER GREGORY S. , KOSKELA ERKKI , OLLIKAINEN MARKKU
Published: August 2010

ABSTRACT.This paper extends the Hartman model to study the optimal rotation age of two interdependent stands at the steady state, when the rotation ages of the two stands are equal and the stream of amenities produced from the two stands may be complements or substitutes, both in space and over time. In the presence of stand interdependence both the ownership structure and the sequence of decision making matters. Rotation age choices are examined and compared under a variety of equilibria, including Nash, Stackelberg and sole owner cases. We show that the sole owner's rotation age is longer than the rotation age under both Nash and Stackelberg assumptions if the stands are spatial complements but shorter if they are spatial substitutes. The precise relationship between the Nash and Stackelberg rotation ages and the qualitative properties of rotation ages in terms of timber prices, regeneration costs and interest rates also depend on how spatial substitutability and complementarity between stands evolves through time.
VIABILITY MODEL OF TROPHIC INTERACTIONS IN MARINE ECOSYSTEMS
Authors: MULLON CHRISTIAN , CURY PHILIPPE , SHANNON LYNNE
Published: August 2010

ABSTRACT. An attempt to use viability models for studying marine ecosystems is proposed as a possible alternative to classical ecosystem modeling. Viability models do not consider optimal solutions but instead define all possible evolutions of a dynamical system under given constraints. Applied to marine ecosystems, a viability model is formulated based on the trophic coefficients of a mass‐balanced model. This requires relatively few assumptions about the processes involved and can integrate uncertainty associated with the required estimates of input parameters. An iterative algorithm is proposed to calculate the viability kernel, i.e., the envelope of all viable trajectories of the ecosystem. An application to the Benguela ecosystem is presented, considering interactions between detritus, phytoplankton, zooplankton, pelagic fish, demersal fish and fisheries. Results show how a viability kernel could be used to better define the healthy states of a marine ecosystem, by defining what states should be avoided. The paper discusses how viability models of trophic interactions could help to define a new ecosystem‐based indicator for fisheries management. It then discusses how this approach can potentially contribute to a paradigm shift that is emerging in the management of renewable resources.
BIOECONOMIC INTERACTIONS IN AN ESTABLISHED FISHING EXCLUSION ZONE: THE GULF OF CASTELLAMMARE, NW SICILY
Authors: MARDLE S. , JAMES C. , PIPITONE C. , KIENZLE M.
Published: August 2010

ABSTRACT. Fishing exclusion zones have become a key management tool for habitat protection and species conservation within fisheries. In many instances, where overfishing or habitat destruction is taking place, they are being promoted strongly. For fisheries management, their use is widespread and their popularity growing. It is clear that in some cases marine protected areas may be crucial to sustaining resources. Most research to date has considered the biological or ecological effects of such reserves. However, little real analysis has been published that takes into account the links between the biology and the economics of the fisheries involved, making the economic benefits to fisheries less clear. This paper considers an exclusion zone which was implemented in 1990 in the Gulf of Castellammare, Sicily in the form of a trawl ban, modeling the potential effects of future policy in this area. The success of the trawl ban has far exceeded expectations, and it is simulated that it may be advantageous, under strict conditions, to relax the ban in part for some of the year.
POPULATION EXTINCTION IN DETERMINISTICAND STOCHASTIC DISCRETE‐TIME EPIDEMIC MODELS WITH PERIODIC COEFFICIENTS WITH APPLICATIONS TO AMPHIBIAN POPULATIONS
Authors: EMMERT KEITH E. , ALLEN LINDA J.S.
Published: August 2010

ABSTRACT. Discrete‐time deterministic and stochastic epidemic models are formulated for the spread of disease in a structured host population. The models have applications to a fungal pathogen affecting amphibian populations. The host population is structured according to two developmental stages, juveniles and adults. The juvenile stage is a post‐metamorphic, nonreproductive stage, whereas the adult stage is reproductive. Each developmental stage is further subdivided according to disease status, either susceptible or infected. There is no recovery from disease. Each year is divided into a fixed number of periods, the first period represents a time of births and the remaining time periods there are no births, only survival within a stage, transition to another stage or transmission of infection. Conditions are derived for population extinction and for local stability of the disease‐free equilibrium and the endemic equilibrium. It is shown that high transmission rates can destabilize the disease‐free equilibrium and low survival probabilities can lead to population extinction. Numerical simulations illustrate the dynamics of the deterministic and stochastic models.
COALITION FORMATION IN A GLOBAL WARMING GAME: HOW THE DESIGN OF PROTOCOLS AFFECTS THE SUCCESS OF ENVIRONMENTAL TREATY‐MAKING
Authors: EYCKMANS JOHAN , FINUS MICHAEL
Published: August 2010

ABSTRACT.We combine new concepts of noncooperative coalition theory with an integrated assessment model on climate change to analyze the impact of different protocol designs on the success of coalition formation. We analyze the role of “single versus multiple coalitions,”“open versus exclusive membership,”“no, weak and strong consensus about membership” and “no transfers versus transfers.” First, we want to find out whether and how modifications of the standard assumptions affect results that are associated with the widely applied cartel formation game in the noncooperative game theoretic analysis of international environmental agreements. Second, we discuss normative policy conclusions that emerge from the various modifications. Third, we confront our results with evidence on past international environmental treaties and derive an agenda for future research.
THE VALUE OF SHORT‐RUN CLIMATE FORECASTS IN MANAGING THE COASTAL COHO SALMON (ONCORHYNCHUS KISUTCH) FISHERY IN WASHINGTON STATE
Authors: KAJE JANNE H. , HUPPERT DANIEL D.
Published: August 2010

ABSTRACT. . In recent years our understanding of the intricate connections between climate variability, marine and freshwater environmental conditions and the responses of fish stocks has improved considerably. With predictable relationships between the environment and stock abundance, fishery managers should be able to forecast variation in stock survival and recruitment. Such forecasts present an opportunity for increasing the economic value of fisheries and for achieving other management objectives, such as stock conservation and maintenance of population diversity. After describing a 4‐step framework for addressing the question ‘What is a forecast worth?’ in a fishery decision‐making context, we introduce the management system for Washington's coastal coho salmon (Oncorhynchus kisutch) fishery. Then we apply the 4‐step framework to estimate the value of improved run size forecasts in the annual harvest management of coho salmon in Washington State. Our principal analytical tool is a stochastic simulation model that incorporates the main characteristics of the fishery. The paper concludes with a discussion of opportunities and constraints to the use of climate‐based forecasts in fishery management on various spatial and temporal scales, and we consider the challenges associated with forecasting variations in fish stock size caused by shifts in climate and related ocean conditions.
HUMAN FERTILITY DECISIONS AND COMMON PROPERTY RESOURCES: A DYNAMIC ANALYSIS
Authors: RUSESKI GORAZD , QUINN JOHN
Published: August 2010

ABSTRACT. In rural areas of developing countries, parental decisions on number of offspring may be made on the basis of the role of children in harvesting local common property renewable resources. It has been argued that this may lead to a cycle of human over‐population and resource over‐exploitation. To investigate the plausibility of this argument, we present a discrete dynamic model with two state variables representing human population level N and resource stock level S. The model is similar to one given by Nerlove and Meyer but differs in several important respects. It is assumed that, in each over‐lapping generation of parents and children, parents decide how many children to have based on their resulting share of the local resource harvest and the costs associated with child‐rearing. Using simulation and analytical methods, the long term steady state population and resource stock levels for this dynamic noncooperative game are contrasted with the steady state when parental fertility decisions are made in a cooperative manner.
ACCOUNTING FOR TEMPERATURE IN PREDATOR FUNCTIONAL RESPONSES
Authors: LOGAN J. DAVID , WOLESENSKY WILLIAM
Published: August 2010

ABSTRACT. A rational mechanism that integrates temperature‐mediated activity cycles into standard predator functional responses is presented. Daily temperature variations strongly influence times that predators can search for prey, and they affect the activity periods of prey, thereby modifying their detection by predators. Thus, key parameters in the functional response, the search time and the detection, become temperature‐dependent. These temperature mediated responses are included in discrete‐time population growth models, and it is shown how environmental temperature variations, such as those that may occur under global climate change, can affect population levels. As an illustration, a logistic growth model with a stochastic, temperature‐dependent predation term is examined, and the response to both average temperature levels and temperature variability is quantified. We infer, through simulations, that predation and prey abundance are strongly affected by mean temperature, temperature amplitudes, and increasing uncertainty in predicting temperature levels and variation, thus confirming many qualitative conclusions in the ecological literature. In particular, we show that increased temperature variability increases oscillations in the system and leads to increased probability of extinction of the prey.
AN INDIVIDUAL‐BASED MODEL FOR TRADITIONAL FORAGING BEHAVIOR: INVESTIGATING EFFECTS OF ENVIRONMENTAL FLUCTUATION
Authors: KANAREK ANDREW R. , LAMBERSON ROLAND H. , BLACK JEFFREY M.
Published: August 2010

AbstractWe present an individual‐based model to simulate the evolution of traditional foraging strategies in a fluctuating environment. The parameters and procedures are based on observed behavior of barnacle geese,Branta leucopsis, during spring staging off the coast of Helgeland, Norway. Within a temporally and spatially heterogeneous environment, goose movement is modeled according to state‐dependent site selection decisions that maximize food intake. The aim of each individual is to optimize fitness (survival and reproduction) by gaining enough food (energy reserves) during 3 weeks of foraging to meet a threshold of energy necessary for successful reproduction. The geese return to the same islands each year and on a daily basis choose unoccupied sites according to their rank in the population‐structured dominance hierarchy, memories of previously visited sites (tradition), past reproductive success, inherited genetic influence towards site faithfulness and/or site quality, and knowledge of the available biomass density. It is assumed that with each subsequent return to a specific location, increased familiarity of the area will benefit an individual through greater food acquisition by more efficient foraging practices. In the event of variable environmental conditions, geese are faced with a critical decision to return to previously visited sites or abandon tradition to explore for something better. It is shown that habitat quality plays an integral role in population dynamics. Beyond the scope of this paper, the evolution of foraging strategies that directly affect reproductive potential is shown to inevitably determine the resilience of the population over time (Kanarek [2006]). Further experiments are required for detailed results and analysis of specific circumstances that provoke the adaptation of certain behaviors. In general, this modeling approach has the potential to reveal significant insight into the emergence of stable responses to environmental disturbance.
OPTIMAL DISCOUNTING OF BENEFITS FROM CLEANUP AT WASTE SITES
Authors: LYON KENNETH S. , CALIENDO FRANK
Published: August 2010

AbstractThis paper uses a general equilibrium optimal growth model to discuss the role of optimal discounting of future benefits from cleanup at high‐level toxic waste sites. Cleanup simultaneously generates two streams of benefits. One of these is directly from utility and the other is indirectly from the added productivity of workers. We note that the optimal discount rate is different for these two types of benefits. Along the optimal path, the former are discounted at the rate of time preference and the latter at the market rate of interest. We achieve this by identifying four components of the shadow value of the stock of toxic waste. These are the utility, productivity, cost, and abundance effects.

The distinction between discount rates appears to have been overlooked in the literature but has significant implications for environmental cost‐benefit analysis due to the growing interest in applying zero time preference to environmental problems, (like waste cleanup) whose consequences extend many generations into the future. A numerical example is included to illustrate these concepts.