The purpose of this study was to examine the effects on the Swedish moose populationof a new moose management system introduced in 2012. To this end, the size of thepopulation had to be measured. The methodology used was an empirical version of theGordon–Schaefer bioeconomic model previously employed to estimate Sweden’s wildboar population. The Effort variable for the model was modified in that traffic accidentsrelative to traffic density served as a proxy for it. The study investigated years for whichdata was available, namely 2004–2017. Nineteen out of Sweden’s 21 Counties wereincluded in the study. The result produced extremely high population estimates,suggesting that the model could not be directly transferred from wild boar to moose.Nonetheless, although the study’s population estimates in absolute terms are unrealistic,their relative sizes indicate that moose populations were somewhat smaller in 2017 thanin 2012 – the latter year being when the new management system was introduced.However, the trend line shows that, over a longer period, the moose population hasincreased in Sweden, and 2017 may just be a temporary deviation from that trend. Itappears, therefore, that Sweden’s latest moose management system does not have thedesired effect on its moose population.

Master of Science / Entomology / Brian McCornack / Several lepidopteran species infest developing panicles. Larval identification is challenging and time intensive, so current recommendations are often simplified by treating all larvae equally across species. Consequently, the yield-loss model developed for corn earworm (Helicoverpa zea) by Buckley and Burkhardt (1962) has been the foundation for management recommendations in modern sorghum Integrated Pest Management (IPM) programs for the last 49 years. Additionally, although pest populations primarily include both fall armyworm (Spodoptera frugiperda) and corn earworm, only a single species damage estimate is used in economic threshold (ET) and economic injury level (EIL) calculations despite multi-species infestations. This research demonstrates both the validation of current management recommendations for corn earworm and the verification of previously assumed damage potentials for fall armyworm feeding in developing sorghum panicles. These results have important implications for sorghum producers faced with making a management decision for multi-species infestations.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The goal of this study is to develop Density Management Diagrams for Eucalyptus grandis W. Hill, which will serve as auxiliary models to establish the variation of appropriate density, and the management group, to conduct settlements with the economic evaluation of management employees schemes. To study area were used stands in full density in reduced spacing, located in Rio-grandense Eastern center and Porto Alegre metropolitan in Rio Grande do Su states mesoregions. Of the density models tested, Tang showed good accuracy, with adjusted coefficient of determination of 0,74 and 3,17% coefficient of variation, which served as the base model for determining the population density rates, competition areas, construction of Management Density Diagrams and the size of the average diameter at the time that starts self-thinning for trees planted per hectare density. It was shown that the value of the slope calculated for the model of Tang, was different from that proposed by the author, worth -3/2 of self-thinning law. It was observed that the average diameter size at the time of the start self-thinning occurs with the removal of the population individuals varies considerably with the tree planting density. Preferably, you should lead the development trajectory of the density of trees per hectare below the line of maximum density, where the line of imminent mortality occurs. With reference to the standard diameter of 25 cm was obtained 5 Settlement density index curves describing curves between them proportional exponentially decreasing trends of frequency individuals per hectare with the diameter increment. Management density diagrams with the variables mean diameter, basal area, volume stand density index provided good volumetric estimates per hectare in relation to actual volumes with efficiency of 0,95, indicating good precision. The tested probability distributions, the Weibull function 2 parameters described accurately the frequency of diameters in time, and the re-estimation of its parameters, allowed frequency distributions by diameter class and therefore real development of the stand. The selected trunk shape function was to Hradetzky with determination coefficient of 0,98 and 8.43% coefficient of variation, generating through its integration the estimated volume of the whole stem and parts of it. The Net Present Value of R$ 12.372,35 ha-1 was determined for the management regime with three thinning, at 52,8; 85,4; 121,8 months and last cut at 185,1, higher than the other simulated systems. The Equivalent Annual Value was good and viable economically for all tested systems, the most attractive was the regime where there were two thinnings to 52,8; 85,4 months and last cut at 121,8 months with Equivalent Annual Value of R$1.550,78 ha-1. The internal rate of return was attractive in any of the simulated management regimes, ranging from 6,48% by year in stands without thinning and final cut at 52,8 months at 25,31% by year in stands managed with thinnings at 52,8; 85,4 months and last cut at 121,8 months. The biggest reason benefit on costs was 3.15, obtained in the management regime with two thinning, at 52,8; 85,4 months and last cut at 121,8 confirming the Equivalent Annual Value and Internal rate or return criteria. / O objetivo do presente estudo é elaborar Diagramas de Manejo da Densidade para Eucalyptus grandis W. Hill, que servirão de modelos auxiliares para estabelecer a variação de densidade adequada, e a faixa de manejo, para condução de povoamentos juntamente com a avaliação econômica dos regimes de manejo empregados. Para área de estudo foram utilizados povoamentos em densidade completa em espaçamentos reduzidos, localizados nas mesorregiões Centro Oriental Rio-grandense e Metropolitana de Porto Alegre do Estado do Rio Grande do Sul. Dos modelos de densidade testados, o de Tang apresentou boa precisão, com coeficiente de determinação ajustado de 0,74 e coeficiente de variação de 3,17%, que serviu de modelo base para determinação dos índices de densidade do povoamento, zonas de concorrência, construção dos Diagramas de Manejo da Densidade e a dimensão do diâmetro médio no momento que inicia o autodesbaste para uma densidade de árvores implantadas por hectare. Comprovou-se que o valor do coeficiente angular calculado para o modelo de Tang, foi diferente do proposto por este autor, com valor de -3/2 da lei de autodesbaste. Observou-se que a dimensão de diâmetro médio no momento em que ocorre o início do autodesbaste, com a supressão de indivíduos da população, varia, consideravelmente com a densidade de árvores de plantio. Preferencialmente, deve-se conduzir a trajetória de desenvolvimento da densidade de árvores por hectare logo abaixo a linha de máxima densidade, onde ocorre a linha de iminente mortalidade. Tendo como referência o diâmetro padrão de 25 cm obtiveram-se 5 curvas de Índices de Densidade do Povoamento que descreveram curvas proporcionais entre si com tendências de decréscimo exponencial das frequências de indivíduos por hectare com o incremento diamétrico. Os diagramas de manejo da densidade com as variáveis diâmetro médio, área basal, volume por índice de densidade do povoamento permitiram boas estimativas volumétricas por hectare em relação aos volumes reais com eficiência de 0,95, indicando boa precisão. Das distribuições de probabilidade testadas, a função de Weibull 2 parâmetros descreveu com acurácia a frequência dos diâmetros no tempo, e a reestimativa dos seus parâmetros, permitiu as distribuições de frequência por classe diamétrica e por conseguinte desenvolvimento real do povoamento. A função de forma de tronco selecionada foi a de Hradetzky com coeficiente de determinação ajustado de 0,98 e coeficiente de variação de 8,43%, gerando por meio de sua integração os volume estimados de todo o fuste e de partes dele. O Valor Presente Líquido de R$ 12.372,35 ha-1 foi determinado para o regime de manejo com três desbastes, aos 52,8; 85,4 e 121,8 meses e corte raso aos 185,1 meses, superior aos demais regimes simulados. O Valor Anual Equivalente foi positivo e viável economicamente para todos os regimes testados, o mais atrativo foi o regime onde ocorreram dois desbastes aos 52,8; 85,4 meses e corte raso aos 121,8 meses com Valor Anual Equivalente de R$1.550,78 ha-1. A taxa interna de retorno foi atrativa em qualquer dos regimes de manejo simulados, variando de 6,48 % a.a. em povoamentos sem desbaste e corte raso aos 52,8 meses a 25,31 % a.a. em povoamentos manejados com desbastes aos 52,8; 85,4 meses e corte raso aos 121,8 meses. A maior razão benefício sobre os custos foi de 3,15, obtida no regime de manejo com dois desbastes, aos 52,8; 85,4 meses e corte final aos 121,8 corroborando com os critérios Valor Anual Equivalente e Taxa Interna de Retorno.

Whale-watching provides economic opportunities worldwide and particularly proliferates in developing countries, such as the Philippines. The sustainability of whale-watching is increasingly debated as these activities also negatively impact cetaceans through changes in behavior, communication, habitat use, morbidity, mortality, and life-history parameters. This study evaluated the total annual cost, revenue, and profit of whale-watching operators in Bais, Philippines, and predicted the changes in the population for spinner dolphin Stenella longirostris with varying levels of whale-watching effort. Total revenue was 3,805,077 PHP ($92,478 USD) while total cost was 5,649,094 PHP ($137,294 USD) with a discount rate of ten percent. The total annual profit of whale-watching in Bais was – 1,844,017 PHP (– $44,817 USD). On average, each operator in Bais lost 160,350 PHP ($3,897 USD) per year from whale-watching. Through time, the spinner dolphin population decreased as it was exposed to more vessels, causing effort to increase, and thus decreased profit for operators. Under current whale-watching effort, the spinner dolphin population was predicted to decrease by 94 percent in 25 years. If Bais reduced effort in their operations to only three vessels whale-watching per day, the spinner dolphin population increased to 80 percent of its initial population size. This was the first study to predict the spinner dolphin population and estimate the total annual profit from whale-watching in Bais, Philippines. It provided data to locals for efficient, profitable, and sustainable decisions in whale-watching operations.

Orientador: Guilherme Wolff Bueno / Resumo: O aumento exponencial da população em nível mundial tem crescido a demanda por proteínas de qualidade. Com isto, muitos produtores rurais têm migrado da atividade agrícola para a aquicultura, surgindo propriedades com diferentes níveis de produção de pescado. No entanto, com o desconhecimento das especificidades econômicas e zootécnicas, vários empreendimentos se tornaram insustentáveis economicamente, gerando endividamentos e falência dos negócios. Neste contexto, o objetivo desta pesquisa consistiu em realizar uma modelagem financeira e avaliar o risco econômico da produção comercial de tilápia (Oreochromis niloticus) em sistema de tanques-rede instalados em um reservatório tropical. O estudo é apresentado em dois capítulos, no primeiro avaliamos o risco financeiro e cenários econômicos de fazendas com grandes volumes de produção (VP), áreas aquícolas de 10 a 600 mil m³. No segundo capitulo, a partir das informações obtidas inicialmente desenvolvemos um modelo matemático de predição financeira (MMPF) integrado com o modelo matemático do coeficiente de crescimento térmico (TGC) o qual considerou variáveis de desempenho dos peixes e fatores econômicos da produção. Verificamos que os tanques-rede com volumes superiores a 51 mil m³ apresentam 38,67% de probabilidade de risco financeiro e econômico, com um Payback acima de 10 anos e podem atingir um Valor Presente Líquido (VPL) maior que zero com uma taxa interna de retorno (TIR) menor que 8,67%. Enquanto, fazendas com área infe... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The exponential increase in population worldwide has been growing the demand for quality proteins. As a result, many farmers have migrated their agricultural to aquaculture, in this scenario the fish farms have different levels of scale production. However, the lack of knowledge of fish production and economic conditions, was promoted enterprises economically unsustainable, generating indebtedness and business failure. In this context, the objective of research was to perform a financial modeling and evaluate the economic risk of commercial production Nile tilapia (Oreochromis niloticus) in the cages installed in a tropical reservoir. The study is presented in two chapters. In the first chapter we assess the financial risk and economic scenarios of fish farms with large production volumes (VP), aquaculture areas from 10 to 600 thousand m³. In a second chapter, we used the information obtained from 1th chapter for developed a mathematical model for financial prediction (MMPF) integrated with the thermal growth coefficient mathematical model (TGC) considered fish performance variables and economic factors to tilapia production. We verified that cages with volumes over 51,000 m³ have a 38.67% probability to lower financial and economic risk, obtain a payback over 10 years and result a net present value (NPV) greater than zero with an internal rate of return (IRR) of less than 8.67%. Likewise, fish farms with area of less 50,000 m³ have a 51.17% the probability of financial failu... (Complete abstract click electronic access below) / Mestre

Au cours des dernières décennies, la détérioration de la santé des forêts a entraîné des épidémies fréquentes des ravageurs et pathogènes. Ces phénomènes menacent la capacité des forêts à fournir des biens et services écosystémiques à la société. Il est donc nécessaire de maintenir la santé des arbres et de réduire les effets des parasites et des agents pathogènes. Cette thèse considère trois problèmes de gestion du point de vue économique : l'invasion actuelle, l'invasion attendue d'un agent pathogène, et les attaques d'un parasite endémique. À partir de ces trois problèmes de gestion, la thèse vise à évaluer les impacts des ravageurs et des pathogènes forestiers et à informer sur la manière dont les ressources peuvent être réparties de façon optimale pour assurer la fourniture de biens et de services par la forêt à long terme.Les invasions biotiques ont un impact sur les prix des produits du bois du fait des chocs d'approvisionnement qui, à leur tour, influencent les choix de gestion forestière. Ceci permet d'introduire des effets de réaction entre les dynamiques écologiques et de marché. Le premier article vise à évaluer ces impacts en combinant un modèle d’équilibre partiel avec des modèles de diffusion spatiale et de mortalité, calibrés pour représenter le dépérissement du Frêne en France (causé par le pathogène Hymenoscyphus fraxineus). Les résultats montrent que les impacts dépendent généralement de la distribution des ressources, de la propagation du pathogène et de la structure du marché. On observe que les choix d’adaptation des gestionnaires forestiers (c'est-à-dire les choix de régénération et de récolte) sont une composante non négligeable de la perte de volume totale.Le deuxième article est axé sur la surveillance et le contrôle d’une invasion attendue. La surveillance et la détection précoce des espèces envahissantes sont importantes pour atténuer les dommages et réduire les coûts de contrôle. Dans le cas où plusieurs propriétaires sont concernés, l’effort de surveillance des propriétaires plus proches du point d'introduction n’est pas optimal, car il ne prend pas en compte les effets négatifs de l'invasion dans les propriétés voisines. Grâce à un jeu différentiel, combiné à un modèle épidémiologique, nous avons calculé la solution non coopérative et coopérative. Nous avons conçu un paiement monétaire pour soutenir la coopération en fonction d'une décomposition intertemporelle du système de négociation de Nash. Les résultats nous montrent que ce paiement garantit que l’accord entre les deux propriétaires est crédible et incitatif. Le modèle est calibré pour l’éventuelle invasion du nématode du pin (Bursaphelenchus xylophilus) dans le Massif Landais.L'objectif principal du troisième article est d'adapter la gestion forestière aux perturbations biotiques et abiotiques. On combine le modèle classique de Faustmann avec un modèle dynamique de population de ravageurs et un modèle de tempête pour calculer l'âge de coupe optimale et le bénéfice actualisé en séquence infinie (BASI) pour différents scénarios de perturbations. Le modèle est appliqué aux dégâts de la chenille processionnaire du pin (Thaumetopoea pityocampa) dans les Landes. Nos résultats ont montré que les tempêtes ont tendance à réduire l'âge optimal de la récolte, alors que le parasite tend à l'augmenter. Les éclaircies augmentent la rentabilité et constituent une stratégie de couverture efficace contre les deux risques. Dans le troisième article, nous avons introduit une règle de décision cut-or-keep pour modéliser le problème du propriétaire forestier après une tempête. Ces implications en termes de gestion sont étudiées plus en détail dans le quatrième article. Notre règle de décision conduit à des gains plus élevés (dans environ 75% des cas) qu’en suivant la règle, généralement utilisée en économie, qui consiste à couper et à replanter les arbres survivants indépendamment du niveau de dégâts. / In recent decades, the deterioration of forest health resulted in frequent pests’ outbreaks and the diffuse pathogens’ presence. These phenomena threaten forests’ ability to supply ecosystem goods and services to the society. It is therefore necessary to maintain tree health and reduce pest’s and pathogen’s impacts. This thesis approaches three management problems from an economic perspective such as the current invasion and the incumbent invasion of a forest pathogen as well as the outbreaks of a native pest. Starting from these three pest and pathogen management problems, the thesis aims at assessing the impacts of forest pests and pathogens and, secondly, informing how resources can be optimally allocated for assuring the long-term provision of good and services.Pest and pathogens invasions have an impact on the prices of wood products via supply shocks, which, in turn, influence forest management choices, thus introducing feedback effects between market and ecological dynamics at a large scale. The first paper aims at evaluating these impacts by combining a recursive partial equilibrium model with spatial-explicit pathogen-spread and pathogen-induced mortality models calibrated to represent the ash dieback in France (caused by the pathogen Hymenoscyphus fraxineus). Results showed that impacts are not homogeneous across regions and generally depend on the resource distribution, pathogen spread and market structure. We observed that the behavioural adaptation of forest managers (i.e., regeneration and harvesting choices) is a non-negligible component of the total standing volume loss.The second paper focusses on monitoring and control of an incumbent invasion. Monitoring and early detection of invasive species is important to mitigate the damages and reduce the control costs. However, when multiple decision-makers are involved, the monitoring effort of frontier landowners (landowners closer to the introduction point) is suboptimal because it does not consider the negative impacts of the invasion spreading to neighbouring properties. Through a two-player differential game combined with an epidemiological compartmental model, we computed the non-cooperative and the cooperative solution. We designed a monetary payment to sustain cooperation based on an intertemporal decomposition of the Nash bargaining scheme. We showed that this payment assured time-consistent outcomes, meaning that the ex-ante agreement between the two landowners was credible and self-enforcing. The model was calibrated for the possible invasion of the pine wilt nematode (Bursaphelenchus xylophilus) in south-western France.In the last two papers, the analysis is downscaled from the landscape level to the stand level and concentrates on a native defoliator pest. The main objective of the third paper is to adapt forest management to biotic and abiotic disturbances. The classic Faustmann model was combined with a pest population model and a windstorm model to compute the optimal rotation age and the land expectation value (LEV) for different disturbances scenarios. The model was calibrated for maritime pine (Pinus pinaster) plantations in south-western France and Pine Processionary Moth (PPM, Thaumetopoea pityocampa) cyclical outbreaks. Our results showed that storms tend to reduce the optimal harvest age, whereas PPM tends to increase it. Overall, the impact of PPM on the rotation length prevails and, here, risks increase rather than decrease the optimal rotation length. Thinnings increased profitability and constitute an effective hedging strategy against both risks. In the third paper, we introduced a cut-or-keep decision rule to model the forest owner problem after a storm event. Its economic and management implications are further investigated in the fourth paper. Unlike previous economic studies which assumed clearing and replanting regardless of the level of damages, the cut-or-keep condition led to higher payoffs in roughly 75% of the cases.

Este trabalho aborda um método de otimização dinâmica baseado em modelos bioeconômicos estabelecidos na teoria do controle ótimo, que visa modelar o resultado econômico-financeiro relacionado à atividade de extração dos recursos naturais, de modo que a otimização do resultado financeiro seja controlada por uma extração sustentável desse recurso. Mais especificamente, consideramos a exploração de madeira florestal restrita a uma série de vínculos econômicos e operacionais, bem como à dinâmica de crescimento natural da floresta. Avaliando o uso efetivo dessa metodologia aplicada ao planejamento das concessões florestais e procurando contribuir com o debate a respeito da viabilidade da forma de gestão florestal baseada em concessões florestais no Brasil. / This work addresses a dynamic optimization method based on bioeconomics models established in optimal control theory, which aims to model the economic-financial result related to the activity of extraction of natural resources, so that the optimization of the financial result is controlled by a sustainable extraction of this resources. More specifically, we consider the exploration of forest wood restricted to a series of economic and operational linkages, as well as the dynamics of natural forest growth. Assessing the effective use of this methodology applied to the planning of forest concessions and seeking to contribute to the debate about the viability of forest management form based on forest concessions in Brazil.

Este trabalho aborda um método de otimização dinâmica baseado em modelos bioeconômicos estabelecidos na teoria do controle ótimo, que visa modelar o resultado econômico-financeiro relacionado à atividade de extração dos recursos naturais, de modo que a otimização do resultado financeiro seja controlada por uma extração sustentável desse recurso. Mais especificamente, consideramos a exploração de madeira florestal restrita a uma série de vínculos econômicos e operacionais, bem como à dinâmica de crescimento natural da floresta. Avaliando o uso efetivo dessa metodologia aplicada ao planejamento das concessões florestais e procurando contribuir com o debate a respeito da viabilidade da forma de gestão florestal baseada em concessões florestais no Brasil. / This work addresses a dynamic optimization method based on bioeconomics models established in optimal control theory, which aims to model the economic-financial result related to the activity of extraction of natural resources, so that the optimization of the financial result is controlled by a sustainable extraction of this resources. More specifically, we consider the exploration of forest wood restricted to a series of economic and operational linkages, as well as the dynamics of natural forest growth. Assessing the effective use of this methodology applied to the planning of forest concessions and seeking to contribute to the debate about the viability of forest management form based on forest concessions in Brazil.

The thesis describes various modifications of the predator-prey model. The modifications are considering several harvesting methods. At the beginning a solution and a sensitivity analysis of the basic model are provided. The first modification is the percentage harvesting model, which could be easily converted to the basic model. Secondly a constant harvesting including a linearization is derived. A significant part is devoted to regulation models with special a focus on environmental applications and the stability of the system. Optimization algorithms for one and both species harvesting are derived and back-tested. One species harvesting is based on econometrical tools; the core of two species harvesting is the modified Newton's method. The economic applications of the model in macroeconomics and oligopoly theory are expanded using the methods derived in the thesis.

The paper is focused on the Predator-Prey model modified in the case of harvesting one or both populations. Firstly there is given a short description of the basic model and the sensitivity analysis. The first essential modification is percentage harvesting. This model could be easily converted to the basic one using a substitution. The next modification is constant harvesting. Solving this system requires linearization, which was properly done and brought valuable results applicable even for the basic or the percentage harvesting model. The next chapter describes regulation models, which could be used especially in applying environmental policies. All reasonable regulation models are shown after distinguishing between discrete and continuous harvesting. The last chapter contains an algorithm for maximizing the profit of a harvester using econometrical modelling tools.