565 research outputs found
Innovative approaches to integrated global change modelling
No full textIntegrated models are important tools to investigate the interactions between planetary processes and the growing impacts of human populations - in short: global change. Current models still have significant shortcomings, notably in their representation of socio-economic processes and the feedbacks between these and the environmental system. They are also often not designed with sufficient transparency to enable participation of interested parties or effective communication with stakeholders and policy makers. These deficiencies are discussed and possible directions for improvement are identified. This Thematic Issue provides a collection of papers that offer a number of innovative ideas for remedying these shortcomings using novel methods and approaches
Supporting Landscape-Level Risk Assessment and Decision-Making in Managed Ecosystems Using Novel Modeling Methods
No full textThe process of translating fundamental environmental research into evidence-based policies meant to protect and manage our ecosystems has long fallen short of expectations. Policymakers’ desires for straightforward solutions with short-term, certain outcomes are constantly at odds with the nature of uncertainty in environmental research and decision modeling. The current methodologies of bridging the science-policy gap by encouraging researchers to communicate the uncertainties more clearly in their models and relate the results of individual studies to the entirety of complex decision-making frameworks are inadequate. Through this thesis, I explore the role of research within the boundary of science and policy and the ways in which we might increase the translation from research to evidence-based policy. Three different model frameworks employ three methodologies to reach this goal (1) Contextualize model outputs in previously existing policy frameworks; (2) Utilize environmental indicators as model outputs that are known to resonate with policy-makers and the public; and, (3) Collaboratively construct model structures to match to the pre-existing mental models of policy and decisionmakers. By understanding the balance between model complexity, uncertainty, and interpretability researchers can better understand how to integrate across research, social, and political boundaries to effectively inform policy.</p
America’s Evolving Relationship with Trees: A Statistical Analysis of Social, Economic, and Environmental Drivers of Forest Management
No full textIn the spirit of American individualism, the majority of the United States’ forested landscape is controlled by private landowners, who make autonomous decisions that impact a shared wealth of biodiversity and ecosystem services. It is important to understand not only the forest management decisions made by private landowners, but also the motivations that incentivize these consequential actions. Furthermore, it is useful to have the capacity to infer such insights using publicly available data, and by employing transparent, flexible, and scalable statistical frameworks. This dissertation seeks to elucidate the motivations and actions of private landowners in the United States using a variety of data sources, including Zillow home estimates, the American Community Survey, satellite remote sensing imagery, and the Forest Inventory and Analysis database, and by implementing interpretable modeling frameworks, such as the hedonic pricing method and structural equation modeling. I uncover nuanced insights about human-environmental systems, including (1) a positive feedback loop between affluence and tree-shading in metropolitan areas; (2) the dominance of normative pressures on forest owners’ harvest intentions; and (3) a causal link between invasive insects and the quantity and sizes of harvested trees. Understanding such relationships benefits policymakers, forest managers, and urban planners tasked with optimizing human-natural systems. </p
Essays on Theoretical Methods for Environmental and Developmental Economics Policy Analysis
No full textThis dissertation contributes to the fields of environmental, natural resource and development economics. It contains three essays, each tackling related but different sets of questions by developing theoretical, analytical and econometric methods for policy relevant analysis. In the first essay I develop theoretical models to discuss how fossil fuel firms may respond to anticipated climate friendly policies by intensifying resource extraction from existing reserve bases (green paradox) and/or by reducing investments in expansion of the pool of extractable reserves. In the second essay I construct theoretical models to discuss the design of institutions for regulation of novel climate altering geoengineering technologies by first exploring the dangers of a lack of carbon policy commitment and then suggesting institutional solutions that draw from the monetary policy literature. Finally in the third essay, I consider the design of a multiple cut-off regression discontinuity design and show how it can be used to answer policy relevant questions in development economics in situations involving multiple treatments and treatment conditions. Collectively, the studies involve theoretical ideas and concepts that help understand the impact of policy uncertainty, think about the design of institutions for policy governance and estimate the impacts of past implemented policies.</p
Mechanisms of Dissolved Heavy Metal Removal in a Freshwater Wetland and the Potential for Remobilization
No full textNeuse River Estuary Modeling and Monitoring Project Stage 1: An Examination of Long Term Nutrient Data in the Neuse River Watershed
No full textSelecting among five common modelling approaches for integrated environmental assessment and management
No full textThe design and implementation of effective environmental policies need to be informed by a holistic understanding of the system processes (biophysical, social and economic), their complex interactions, and how they respond to various changes. Models, integrating different system processes into a unified framework, are seen as useful tools to help analyse alternatives with stakeholders, assess their outcomes, and communicate results in a transparent way. This paper reviews five common approaches or model types that have the capacity to integrate knowledge by developing models that can accommodate multiple issues, values, scales and uncertainty considerations, as well as facilitate stakeholder engagement. The approaches considered are: systems dynamics, Bayesian networks, coupled component models, agent-based models and knowledge-based models (also referred to as expert systems). We start by discussing several considerations in model development, such as the purpose of model building, the availability of qualitative versus quantitative data for model specification, the level of spatio-temporal detail required, and treatment of uncertainty. These considerations and a review of applications are then used to develop a framework that aims to assist modellers and model users in the choice of an appropriate modelling approach for their integrated assessment applications and that enables more effective learning in interdisciplinary settings. © 2013 Elsevier Ltd.Rebecca A. Kelly (Letcher), Anthony J. Jakeman, Olivier Barreteau, Mark E. Borsuk, Sondoss ElSawah, Serena H. Hamilton, Hans Jørgen Henriksen, Sakari Kuikka, Holger R. Maier, Andrea Emilio Rizzoli, Hedwig van Delden and Alexey A. Voino
Índice de Yang e teoremas generalizados
No full textWe work with T-spaces (X; T), where X is a Hausdor_ compact space and T : X ! X is a continuous involution without _xed points. Considering the sphere Sn with the antipodal map, we highlight three classical theorems relating to the T-space Sn;A): Borsuk-Ulam's theorem, Kakutani-Yamabe-Yujobô's theorem and Dyson's theorem. This dissertation consists of a detailed study of the article fo C. T. Yang (Annals of Math. 60, no. 2 (1954), 262-282) where the author introduces a concept of the index and presents, in a sense homological, generalizations of the three theorems cited above, considering any T-space. Beyond the generalizations itself, we build examples of the index calculation of some T-spaces and, still, we explore a concept of orthogonality in T-spaces.Universidade Federal de Sao CarlosTrabalhamos com T-espaços (X; T), em que X é um espaço compacto e Hausdor _ e T : X ! X é uma involução contínua sem pontos _xos. Considerando a esfera Sn com a aplicação antipodal, destacamos três teoremas clássicos relativos ao T-espaço (Sn;A): teorema de Borsuk-Ulam, teorema de Kakutani-Yamabe-Yujobô e teorema de Dyson. Esta dissertação consiste em um estudo detalhado do artigo de C. T. Yang (Annals of Math. 60, no. 2 (1954), 262-282) em que o autor introduz um conceito de índice e apresenta, em certo sentido homológico, generalizações dos três teoremas citados acima, considerando T-espaços quaisquer. Além das generalizações em si, construímos exemplos de cálculo de índice de alguns T-espaços e, ainda, exploramos um conceito de ortogonalidade em T-espaços
Improving Structure MCMC for Bayesian Networks through Markov Blanket Resampling
No full textAlgorithms for inferring the structure of Bayesian networks from data have become an increasingly popular method for uncovering the direct and indirect influences among variables in complex systems. A Bayesian approach to structure learning uses posterior probabilities to quantify the strength with which the data and prior knowledge jointly support each possible graph feature. Existing Markov Chain Monte Carlo (MCMC) algorithms for estimating these posterior probabilities are slow in mixing and convergence, especially for large networks. We present a novel Markov blanket resampling (MBR) scheme that intermittently reconstructs the Markov blanket of nodes, thus allowing the sampler to more effectively traverse low-probability regions between local maxima. As we can derive the complementary forward and backward directions of the MBR proposal distribution, the Metropolis-Hastings algorithm can be used to account for any asymmetries in these proposals. Experiments across a range of network sizes show that the MBR scheme outperforms other state-of-the-art algorithms, both in terms of learning performance and convergence rate. In particular, MBR achieves better learning performance than the other algorithms when the number of observations is relatively small and faster convergence when the number of variables in the network is large
A quantitative program for Hadwiger's covering conjecture
No full textIn 1957, Hadwiger made a conjecture that every n-dimensional convex body can be covered by 2(n) translates of its interior. Up to now, this conjecture is still open for all n >= 3. In 1933, Borsuk made a conjecture that every n-dimensional bounded set can be divided into n + 1 subsets of smaller diameters. Up to now, this conjecture is open for 4 <= n <= 297. In this article we encode the two conjectures into continuous functions defined on the spaces of convex bodies, propose a four-step program to attack them, and obtain some partial results.Mathematics, AppliedMathematicsSCI(E)2ARTICLE92551-25605
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