Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item DEVELOPMENT AND EVALUATION OF SPATIALLY-EXPLICIT POPULATION MODELS FOR ESTIMATING THE ABUNDANCE OF CHESAPEAKE BAY FISHES(2024) Nehemiah, Samara; Wilberg, Michael J.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Although fish populations typically experience spatially varying abundance and fishing mortality, stock assessments that inform management decisions commonly model a population that is assumed to be well-mixed with homogenous mortality rates. When assumptions about population mixing are not met, these models can result in biased estimates. Spatial population estimates are particularly beneficial to the Chesapeake Bay because this region faces unique challenges as a result of climate change and fishing pressure. However, use of spatial population models for fisheries management relies on models that can provide more accurate estimates of biological parameters than non-spatial models. Objectives for this research were to 1) develop and implement a multi-stock, spatially-explicit population model for Striped Bass (Morone saxatilis) to estimate abundance and fishing mortality in the Chesapeake Bay and along the Atlantic coast; 2) assess the performance of spatially-explicit models compared to spatially-implicit models (i.e., fleets-as-areas) to estimate abundance, determine how improved data quality (e.g., stock composition) affects model performance, and determine the effect of aging error on model accuracy; and 3) determine how spatial model performance is affected by potential changes in population dynamics resulting from climate change (e.g., time-varying natural mortality). The population model was a two-stock model with two sub-annual time-steps and two regions with stock and age-specific occupancy probabilities representing movement into and out of the Chesapeake Bay. Fishing mortality was estimated to be higher in the Ocean than the Chesapeake Bay, and abundance increased during 1982-2004 for both stocks before declining slightly until 2017. Simulations were conducted to test the ability of models to estimate abundance and fishing mortality under alternative scenarios of data availability and quality. Spatially-explicit estimates were approximately unbiased when they closely matched the assumptions of the data generating model. Models that ignored potential aging bias in datasets resulted in highly biased estimates of abundance and fishing mortality. Although the performance of all models degraded under most climate change scenarios, spatially-explicit models produced the most accurate model estimates compared to fleets-as-areas models. This research highlights the potential benefits of implementing spatially-explicit population models for Striped Bass and ecologically valuable fish species in the Chesapeake Bay.Item The Economics of Spruce Budworm Monitoring and Management in Eastern Canada(2024) Holm Perrault, Alexandre Ismaël Eliot; Olson, Lars J; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation uses techniques that were developed for renewable natural resource and invasive pest management to describe the two principal challenges of eastern spruce budworm (SBW) monitoring and management in Eastern Canada, with a specific focus on the province of Quebec. The primary empirical components of this dissertation can be found in Chapters 2 and 3. Chapter 1 provides the necessary historic, entomological, ecological and policy context to understand Chapters 2 and 3. Chapter 4 provides a conclusion to this dissertation by proposing extensions that would make the models presented in Chapters 2 and 3 more readily applicable to real-world spruce budworm management. These extensions involve making the models spatially explicit, as the models presented in Chapters 2 and 3 are spatially crude for the sake of tractability. Chapter 2 describes the management of an endemic irruptive forest pest and, using the spruce budworm-balsam fir forest interaction, proposes an optimization model that determines optimal pest treatment and forest harvest levels for a single, dimensionless forest stand that is currently undergoing an active budworm outbreak. Budworms cause both growth reductions and mortality on the forest biomass stock, and increasing forest biomass will provide budworms with more prey, causing their growth rate to increase. Treatment decisions are limited to three discrete possibilities (0, 1 or 2 on the landscape) that impose mortality on budworms, while harvests remove a proportion of the forest biomass. Using a numerical solution algorithm, we find that the optimal policy is generally to apply treatments over budworms and to harvest the forest at a sustainable rate, which confirms that the current management programs used in Eastern Canada are welfare-improving relative to letting an outbreak run its course. The time path for our baseline scenario indicates that budworms can be treated down to endemic levels quickly. Sensitivity analysis describes scenarios where budworm levels will rebound every year as well as scenarios where the optimal policy is to clearcut the forest as quickly as possible. Chapter 3 considers the pre-outbreak monitoring phase for spruce budworm management. This context is informed by the Early Intervention Strategy, a management practice that is currently being successfully employed in New Brunswick and other Maritime provinces. EIS requires extensive monitoring and proactive treatment. As such, we adapt a model known as CESAT to determine the locations for which EIS would yield positive net benefits in eastern Quebec. Under our baseline scenario, we find that EIS is optimal in some zones bordering New Brunswick, which indicates that EIS is unlikely to be welfare-improving over current management practices used in Quebec. Under different assumptions, however, we find that EIS is optimal across a much larger landscape, yielding millions of CAD net benefits over a thirty year horizon.Item DESIGNING AN ACCESSIBLE AGRICULTURAL GARDEN: CONNECTING SOLIDARITY & AGROECOLOGY(2024) Boyle, Patrick Robert; Ruggeri, Deni; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis explores the potential of agroecology as a transformative framework for guiding the transition of Bergamo's agricultural landscape toward sustainability, resilience, and community well-being. Grounded in the evolution of agroecology from farm-scale design to regional planning, the research investigates how this approach can integrate ecological methodologies and participatory action research in design to implement sustainable farming practices, rehabilitate landscapes, and cultivate solidarity-driven producer-consumer relationships. By emphasizing the interconnectedness of ecology, economy, and society, the study addresses whether agroecology can shape a district into a resilient landscape that enhances people's lives and promotes health and well-being.Through an interdisciplinary lens, the thesis also delves into the broader concept of landscape, highlighting its role in social well-being and advocating for the protection and responsible management of landscapes as a fundamental human right. It explores the principles of landscape democracy and solidarity, aiming to empower communities to reconnect with their environments and promote ecological restoration through collective action and ethical practices. Ultimately, the research strives to contribute to the discourse on agroecology and landscape planning, offering proposals and strategies for actionable change in regenerative and organic agricultural systems that prioritize the needs and values of local communities.Item EFFECTS OF ENVIRONMENTAL VARIABLES AND CHANGES IN SEASONAL PATTERNS ON SPATIAL DISTRIBUTIONS OF JONAH CRABS (CANCER BOREALIS) AND ATLANTIC ROCK CRABS (CANCER IRRORATUS) IN GEORGES BANK AND THE MID-ATLANTIC BIGHT, USA(2023) Wade, Kaitlynn Jean; Wilberg, Michael J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The economic and commercial importance of Jonah crabs (Cancer borealis) and Atlantic rock crabs (Cancer irroratus) has increased greatly in the USA. The objectives of my research were to determine spatial distributions, habitat preferences, and potential seasonal movements of both species. Data were obtained from the offshore Northeast Fishery Science Center bottom trawl surveys. Analyses included kernel density estimates, generalized additive models, empirical cumulative distribution functions, and ANOVAs. The spatial distributions of Jonah and Atlantic rock crabs changed over time during the 1970s – 2000s. Compared to Atlantic rock crabs, Jonah crabs preferred slightly warmer temperatures, deeper depths, and muddier sediments. Seasonally, Jonah crabs were found farther offshore in the winter and closer to shore in the fall and spring. Atlantic rock crabs were found closer inshore in the winter and spring and more offshore in the fall. Both species were found to have different seasonal patterns in the Mid-Atlantic BightItem Investigating the Utility of Environmental DNA Analysis for the Monitoring and Management of Mid-Atlantic Alosine Fishes(2023) Fowler, Chelsea; Plough, Louis V; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Environmental DNA (eDNA) tools can address gaps in fish assessment data while reducing the cost and the impact of sampling on threatened anadromous alosine fishes in Chesapeake Bay. Here, I tested the ability of high-frequency eDNA sampling of river herring to predict fish abundances from sonar-based fish counts on the Choptank River and developed and validated novel species-specific eDNA assays for American and hickory shads. River herring eDNA concentrations from daily eDNA sampling were highly correlated to sonar-based fish counts (Spearman’s Rho = 0.84). This relationship informed a model that could accurately predict fish count from eDNA and relevant covariates (R2 = 0.88). The two new shad assays are highly specific and quantitative, and field testing validated detections in Delaware, Maryland, and North Carolina. This work provides a set of eDNA monitoring tools for the Mid-Atlantic alosines and highlights the capacity for eDNA data to generate quantitative metrics of fish abundance.Item LEVERAGING FINE-SCALE GEOSPATIAL DATA TO ADVANCE BIODIVERSITY SENSITIVE URBAN PLANNING, WILDLIFE MANAGEMENT, AND GREEN CORRIDOR DESIGN: APPLICATION TO THE DISTRICT OF COLUMBIA(2023) Spivy, Annette Leah; Mullinax, Jennifer; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Typically, urban wildlife communities are made up of generalist species that are adept at utilizing human resources. However, many wildlife species struggle in the face of extensive urbanization and would benefit from increased conservation of urban green space, increased urban landscape connectivity, and proactive wildlife population management strategies. Unfortunately, maintaining and/or increasing the availability of quality habitat for biodiversity conservation in urban areas can be challenging as these conservation efforts are often influenced by the decreasing availability of critical resources and the challenges in allocating those resources among competing socioeconomic and environmental needs. Therefore, to improve the management and conservation of urban wildlife, accurate measurements of potential trade-offs between the environmental, economic, and social goals and management actions of a city’s sustainable development plan are needed. Until now, much of the effort in wildlife habitat modeling and biodiversity mapping has been across large geographic areas or broad spatial scales. Those efforts have provided valuable insights into overall biodiversity patterns, identifying key hotspots, and understanding large-scale ecological processes. However, in urban environments, the dynamics of wildlife, habitat availability, and ecosystem services operate differently than in natural or rural landscapes. As urbanization continues to expand, there is a growing need to focus on fine-scale factors to address specific conservation challenges in urban systems. This research seeks to address some of these challenges and demonstrates how new and traditional species-relevant geospatial datasets can be leveraged in urban planning and design to drive local-scale conservation decisions that put biodiversity in the forefront. This work links long-term, multi-taxon, wildlife survey data and high-resolution land use and land cover datasets (1m) to determine where high-quality, well-connected habitats exist, or could most easily be justified and acquired, within the District of Columbia. This work also evaluates the spatial patterns of ecosystem service provisions across the urban landscape to identify “win-win” areas for conservation or restoration that will benefit both biodiversity and human wellbeing. Finally, the work evaluates a local translocation effort of the vulnerable eastern box turtle (Terrapene carolina carolina) to inform mitigation strategies when a sudden loss of habitat in an urban environment is inevitable. This research is particularly relevant to wildlife managers and urban planners in highly urbanized areas, where large parcels of land with suitable habitat are minimal and municipal environmental departments are often under-resourced. Local policymakers interested in incentivizing conservation efforts to meet state or national goals can use this information for strategic urban conservation initiatives.Item Expanding the Fisheries Management Tackle Box: A Multiple-Model Approach to Support Better Decisions(2023) Hayes, Christopher Glenn; Wainger, Lisa; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Marine fisheries provide critical ecosystem services but face an array of stressors like climate change and overfishing. Managing fisheries is challenging due to limited information and the need to make complex tradeoffs among ecological and social objectives. Decision processes that include integrated social-ecological models and equitable stakeholder engagement are increasingly recognized as approaches to improve the likelihood of achieving management goals compared to those that rely solely on stock assessment models with limited stakeholder input. Additionally, advanced technologies offer new opportunities to understand marine ecosystem dynamics, including human behavior. This research adds two examples of underutilized tools: multi-criteria decision analysis (MCDA) and agent-based models (ABMs). In the first case, I compared management recommendations for the Chesapeake Bay oyster fishery arising from A) stakeholder engagement using group negotiations and B) preferences elicited from individuals using an MCDA approach. The recommendations were consistent across methods, suggesting that group effects did not bias group negotiation outcomes. The second case investigated New England groundfish reporting behavior based on stock dynamics, quota markets, and fishery observer coverage. First, having an observer onboard was found to significantly reduce the probability and magnitude of reporting error (ie., an observer effect) using a linear mixed effects model of data from vessel trip reports and remote vessel monitoring systems. Next, an ABM was used to explore emergent responses to policy changes - varying levels of observer coverage and the strength of the observer effects - on fish catch, reporting error, and profit outcomes, given fisher interactions and responses to fish population dynamics. Scenarios with strong observer effects resulted in increasing marginal improvements in reporting accuracy at high levels of observer coverage. MCDA and ABM can contribute to a multiple-model approach by allowing fisheries managers to integrate diverse stakeholder perspectives and use additional data sources that could lead to better fishery outcomes.Item TOOL DEVELOPMENT TO CONSTRAIN AND OPTIMIZE SHELLFISH AQUACULTURE GEAR PERFORMANCE(2022) Campbell, Brendan; Gray, Matthew W; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)To produce virginica cultured Crassostrea more efficiently, current grow out techniques require better understanding to allow for more consistent growth and quality. While the basic physical conditions that influence shellfish growth have been well researched, there are limited studies that consider how physical conditions (i.e. water flow and wave motion) influence shellfish growth within the context of an off-bottom aquaculture farm. Since oysters are suspension feeders, they require food to be delivered to their siphons through ambient processes. Changes in water flow can influence the overall survival, growth rate, and quality of oysters. Additionally, the motion, or jostling, of cages are thought to cause chipping on the outer portion of oyster shells, influencing the overall shape and growth of oysters. There are many techniques and equipment that have the potential to influence the water delivery and movement of oysters in containerized culture; however, little research has addressed how culture practices influence physical forcing surrounding cultured oysters and what impact those changes have on oyster performance. The biophysical relationship occurring in shellfish aquaculture is not being properly characterized partially due to a lack of affordable tools capable of monitoring physical forces in constrained spaces. This dissertation summarizes the current understanding of how culture practices influence oyster aquaculture production and demonstrates the novel use of affordable and commonly available tools that can be utilized in shellfish aquaculture research across multiple operational scales. The development of a novel clod card method and predictive model was attempted for use in characterizing mass transfer rate of water. The clod card, along with accelerometer loggers were utilized to understand the effects of physical forcing on the production of off-bottom cultured oysters when exposed to a range of biofouling mitigation treatments, grown using different culture methods, and spatially across an active shellfish aquaculture lease. These experiments validated the value in characterizing physical forcing in shellfish aquaculture and identified trade-offs between oyster shell growth and market quality that are linked to changes in the physical environment, which were produced by changing culture practices. Additionally, these validation experiments determined that variability in oyster growth and performance can change over small spatial scales, smaller than the typical grow-out shellfish aquaculture lease, which can influence water movement inside cages, water quality, and the efficiency of a commercial shellfish operation. By considering the local physical environment, growers can strategically employ culture practices that optimize the water flow through and movement of oysters to enhance farm profitability.Item FOREST CHANGE AND OIL PALM EXPANSION IN INDONESIA: BIOPHYSICAL AND SOCIOECONOMIC ANALYSIS(2022) Xin, Yu; Sun, Laixiang; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Palm oil is the world's most widely used edible oil, and Indonesia has been the largest producer since 2007 and now makes up around 58% of the global market. The oil palm production has benefited the economic growth and lifted the living standards of local people in Indonesia, but this gain is often at the cost of replacing tropical forest, destructing peatland, inducing greenhouse gas (GHG) emissions, and reducing biodiversity. The expansion of oil palm plantation in Indonesia is bound to increase as the global demands continue to grow. The challenge of meeting the increased demand for oil palm products while effectively protecting tropical forest and its ecosystem services is an important tradeoff issue for both scientists and policymakers. However, little is known on the expansion patterns of oil palm in Indonesia, especially the underlying drivers with temporal and spatial details. To effectively address the knowledge gaps and deal with the challenges, this dissertation aims to first characterize the historical patterns driven by the variations in the benefits and costs of oil palm expansion across space and over time. It then projects the possible future spatial patterns and estimates the potential loss of land with high environmental values in order to meet the future global demand for oil palm products. This dissertation consists of three principle essays. The first essay identifies the major land sources of oil palm expansion in Indonesia with temporal details, and reveals the joint role of biophysical and socioeconomic drivers in shaping the spatial patterns of oil palm expansion by employing spatial panel models at the regency level. The second essay focuses on the temporal dynamics of the biophysical and socioeconomic drivers and the timing of estate crop (mainly oil palm) expansion by using Cox proportional hazard models (CPHMs) and their extensions with time-variant effects at the 1km × 1km grid level. It also explores the role of land use and land cover change (LCLUC) trajectory hopping in estate crop expansion into natural forest by introducing multi-state survival analysis to land-use science. The third essay projects the export demand for oil palm products from Indonesia by 2050 under different global trade scenarios with generalized geo-economic gravity models, and quantifies the possible tradeoffs between oil palm expansion and environmental conservation by allocating the projected demand to 1km × 1km grids across Indonesia applying parametric survival analysis. This study indicates that oil palm expansion in Indonesia has been strongly stimulated by the export value of oil palm products and prefers land with good biophysical suitability and infrastructure accessibility. As land resources become more limited, the effects of socioeconomic factors decrease following the ‘pecking order’ sequence, and the plantation expands into remote but fertile areas with high conversion costs or legal barriers. The degraded land surpassed natural forest and became the major direct land source of oil palm expansion in recent years, but degraded land had increasingly served as a land banking mechanism and a clearing-up tactic. This LCLUC trajectory hopping mechanism has made the protected area (PA) designations and sustainable development requirements become less and less effective in protecting tropical natural forest. Lowland secondary forest and peatland are the high-environmental-value (HEV) areas with the highest risks of conversion to oil palm plantation. To cope with the LCLUC trajectory hopping mechanism, Indonesia needs to have well-designed and fully enforced policies which limit/ban expansion into protected areas, peatland conversion, and deforestation of both primary and secondary forest. The country also needs more effective economic compensation mechanisms to promote more environment-friendly oil palm plantation. In this way, it is possible for Indonesia to maintain its leading position in oil palm production and exportation, while enhancing its role in environmental protection, such as climate change mitigation and biodiversity conservation. This dissertation improves our understanding of oil palm expansion in Indonesia by integrating economic science theory, advanced econometric techniques, and the best available remote-sensing data. It adds to the existing literature on analyzing the impacts of human behaviors on LCLUC at various spatial and temporal scales, especially from a longitudinal perspective.Item STAKEHOLDER CHALLENGES AND OPPORTUNITIES: APPLYING A SOCIO- ECOLOGICAL FRAMEWORK TO INTEGRATE HUMAN DIMENSIONS WITH U.S. WILDLIFE MANAGEMENT(2021) Gedeon, Taylor Marie; Shaffer, L. Jen; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Wildlife practitioners face growing pressures to work at the interface of ecological and social issues yet the model they use in the United States, the North American Model of Wildlife Conservation (NAMWC), relies heavily on natural sciences. Inclusion of social science perspectives is needed to provide a consistent methodology to assess the current and desired conditions of both wildlife and humans. Current state wildlife practitioners offer a unique perspective into the challenges that exist barring this integration. Through semi-structured interviews with wildlife managers in Maryland and Florida, this research explores current definitions of the term stakeholder, stakeholder role, agency role, and the applicability of a socio- ecological approach for native versus nonnative species. Interviews revealed inherent issues with the NAMWC, and challenges and opportunities for the integration of human dimensions. By understanding existing challenges and opportunities, agencies can begin to develop holistic solutions for the increasing demands of human-wildlife conflict.