UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

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ESSAYS ON THE DESIGN AND EVALUATION OF PAYMENTS FOR ECOSYSTEM SERVICES PROGRAMS
(2024) Kim, Youngho; Lichtenberg, Erik; Newburn, David; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Nature-based solutions for climate change mitigation and adaptation emphasize the restoration of natural infrastructure and the adoption of conservation practices in agriculture. Payment for ecosystem services (PES) programs play a key role in these efforts by offering financial incentives to farmers and landowners who adopt land use or management activities that provide environmental amenities and services for society. This dissertation consists of three chapters that examine the optimal design of PES programs and evaluate their performance in the context of climate change and environmental protection. The first chapter investigates whether PES programs contribute to climate change adaptation by reducing economic losses from extreme weather events. I evaluate the cost-effectiveness of the Conservation Reserve Enhancement Program (CREP) in the United States in mitigating flooded crop losses through the restoration of riparian buffers and wetlands. By leveraging variation in the timing of program introduction across counties in the Mississippi River Basin, I find that the introduction of CREP reduced both the number of flooded acres and the extent of damage on those acres. CREP also generated financial spillover effects on the federal crop insurance program, reducing indemnity payouts that would have otherwise been allocated to insured farmers. This study enhances our understanding of how PES programs promote sustainable agriculture and facilitate nature-based solutions for climate change adaptation. The second chapter examines the cost-effective structure of payments and penalties in PES programs, in collaboration with Erik Lichtenberg and David Newburn. The sustainability of ecosystem services programs is contingent on landowners’ compliance with the signed contracts after their initial participation. However, premature contract terminations are not uncommon, particularly when unexpected increases in crop prices lead to the removal of established conservation cover on agricultural land. In such cases, PES programs typically require participants to repay all payments received up to the date of contract termination (e.g., those in the US, the EU, Costa Rica, Mexico, Australia, and many other countries). This standard penalty structure is inefficient because it directly couples penalties with payments, increasing monotonically during the contract period. This study is the first to derive the optimal penalty structure that equals net environmental benefits for the remaining contract period, which decouples penalties from payments. A numerical policy simulation using integrated assessment models shows that the U.S. federal PES programs can substantially increase the environmental benefits by restructuring the current standard penalty. Importantly, the optimal penalty tends to decrease gradually during the contract period, providing credit to farmers for the ecosystem services generated prior to the contract termination. This finding has broad implications for restructuring PES programs in the U.S. and globally, and the study has been published in the Journal of Environmental Economics and Management. The third chapter examines the influence of U.S. federal agricultural conservation programs on the performance of emissions trading programs in promoting afforestation activities on agricultural land, in collaboration with Erik Lichtenberg, David Newburn, Haoluan Wang, and Derek Wietelman. Emissions trading programs, which pay for performance, have been advocated as flexible and efficient tools for achieving pollution reduction goals when evaluated in isolation. However, these programs often operate within a policy landscape dominated by conservation subsidy programs that pay for effort. We find that current federal conservation subsidies are so generous that they significantly crowd out water trading programs when both are in competition, although water trading programs would be effective in isolation. In addition, current carbon market payments for offsets are insufficient to make emissions trading programs more attractive compared to longstanding agricultural conservation subsidy programs. While prior studies have attributed low farmer participation in emissions trading programs to transaction costs and market uncertainty, our analysis suggests that even if these impediments are removed, competition with existing pay-for-effort programs would remain a significant barrier to expansion of emissions trading among agricultural producers. Therefore, the attractiveness and effectiveness of emissions trading programs for afforestation depend heavily on the presence and generosity of longstanding federal agricultural conservation subsidies.
CLIMATE CHANGE RELATED EXTREME EVENTS AND ADVERSE HEALTH OUTCOMES AMONG HEMODIALYSIS PATIENTS
(2024) Song, Hyeonjin; Sapkota, Amir AS; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The increased frequency and intensity of extreme heat events (EHEs) and wildfires due to climate change are posing significant threats to vulnerable communicates including end-stage kidney disease (ESKD) patients. The specific aims of this dissertation are to Aim 1) Examine the association between EHEs exposure and serum concentrations of sodium and potassium among hemodialysis patients in the Western U.S. (2008-2018), Aim 2) Quantify the mortality and hospitalization risk associated with exposure to 2023 Canadian wildfire-related air pollution in the Eastern U.S., and Aim 3) Investigate how EHEs modify the association between wildfire-related air pollution exposure and the risk of mortality and hospitalization among hemodialysis patients in the Western U.S. (2010-2018). We analyzed health records of patients who receiving hemodialysis treatment at Fresenius Kidney Care clinics. We used the 10°C increase in daily average temperature and daily extreme heat events (EHEs) of each county as the primary exposures. The presence of wildfire smoke plume and wildfire fine particulate matter (PM2.5) concentrations for each clinic were measured using satellite-derived smoke polygons (Hazard Mapping System) and ground-based PM2.5 monitors (Air Quality System). We estimated mean serum sodium and potassium change per 10 °C increase in daily average ambient temperature using random intercepts linear mixed-effects models. We employed a time-stratified case-crossover analysis with conditional quasi-Poisson model to investigate the risks of mortality and hospitalization associated with exposure to wildfire-related air pollution and EHEs. In the first study, a 10°C increase in daily average temperature was associated with 0.43 mEq/L (95% Confidence Interval [CI]: 0.47, 0.59) increase in serum sodium during July-August. The serum sodium was 0.15 mEq/L (95% CI: 0.10, 0.20) higher during EHE days compared to non-EHE days. The serum potassium level did not show a significant change. In the second study, during June-July 2023, the presence of wildfire smoke plume was associated with an 18% increase in all-cause mortality risk (Rate Ratio [RR]:1.18; 95% CI: 1.13, 1.24) and a 3% increase in all-cause hospitalization risk (RR:1.03; 95% CI: 1.00, 1.07). A 10-μg/m3 increase in wildfire-related PM2.5 was associated with a 139% increase in all-cause mortality (RR: 2.39; 95% CI: 1.79, 3.18) and a 33% increase in all-cause hospitalization (RR:1.33; 95% CI: 1.10, 1.62). In the third study, we observed significant interactions between EHEs and wildfire smoke plume for mortality RRs among the hemodialysis patients in the Western U.S. Mortality risk was considerably higher when hemodialysis patients were simultaneously exposed to wildfire smoke plume and EHE compared to wildfire smoke plume alone (RR: 1.52; 95% CI: 1.25, 1.86 vs. RR: 1.15; 95% CI: 1.08, 1.23). We did not observe a significant interaction for all-cause hospitalization. Our findings underscore the need to revise operational and care protocols to prepare for such potential join exposures to extreme events that are exacerbated by ongoing climate change. Future work should focus on developing early warning systems to enhance resilience against such threats.
BREAKWATER – Breaking the Cycle
(2024) Mora, Adrian Bernard Teneza; Gabrielli, Julie; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
How can ecological design principles prevent the erosion of the physical and social framework of low-income coastal communities? A significant portion of the world’s population is concentrated along coastlines. Direct access to the water provides access to a longstanding source of economic prosperity and a psychological connection to natural environments. However, human-influenced climate change has produced hazardous environmental conditions that threaten coastal populations, including many poor, vulnerable communities. Disparities in investment for public services, maintenance, and upkeep increases the vulnerability of these disenfranchised groups that cannot protect themselves. The built and natural environment within this diverse boundary zone between the land and sea must be redeveloped as a self-resilient ecosystem that can protect its inhabitants from climate-induced hazards. This renewal will require holistic approaches that can mitigate contemporary impacts to protect current populations at risk and adapt the built environment to better respond in the future.
ATMOSPHERIC ORGANIC AEROSOLS: THE EFFECT OF PHYSIOCHEMICAL PROPERTIES ON HYGROSCOPICITY
(2023) Malek, Kotiba; Asa-Awuku, Akua; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Aerosols, tiny solid or liquid particles, are ubiquitous in the atmosphere yet their impact on climate remains poorly understood. One prominent way aerosols are able to impact the climate is through their ability to uptake water and form clouds. The chemical diversity and aerosol interactions in the atmosphere can greatly complicate the investigation of aerosol-cloud interactions. This complexity is expressed with a large uncertainty associated with aerosols’ role on climate change. This dissertation investigates the aerosol-cloud interaction by measuring the water uptake of atmospherically relevant aerosols. Our results highlight the importance of accounting for various physiochemical properties when exploring the water uptake of atmospheric aerosols. One such property is liquid-liquid phase separation (LLPS) in ternary mixtures. Our work offers new evidence, insight, and a paradigm shift to the contribution of LLPS to supersaturated droplet activation. We complemented this finding with a theoretical model, that incorporates solubility, O:C ratio, and LLPS, for predicting κ-hygroscopicity of ternary mixtures. Another physiochemical property that was shown to play a key role in droplet activation of polymeric aerosols is chemical structure. Our study shows that polycatechol is more hygroscopic than polyguaiacol and the difference in hygroscopicity is attributed to the density of hydroxyl groups in both structures. Polycatechol has a higher density of hydroxyl groups than polyguaiacol, resulting in polycatechol having stronger water uptake affinity than polyguaiacol. When maintaining the same structural makeup by investigating the water uptake of two isomeric compounds, we discovered that solubility was the driving force in water uptake. The more soluble isomer o-aminophenol was more hygroscopic than p-aminophenol. Hence, a small change in the position of functional groups can impact solubility which in turn influence hygroscopicity. Lastly, we explored the presence of gas-phase organics on the water uptake of isomers with a wide range of solubilities. Our work highlights that gas-phase organics, specifically ethanol, can influence the water uptake of aerosols. Ethanol was shown to increase water uptake efficiencies based on solubility, with the least soluble compound showing stronger affinity to water uptake. Overall, this thesis advances our knowledge and understanding of aerosol-cloud interactions and its implications on climate change.
EXAMINATION OF TROPOSPHERIC OZONE AND ITS PRECURSORS WITHIN AN AIR QUALITY MODEL AND IMPLICATIONS FOR AIR QUALITY AND CLIMATE
(2021) Hembeck, Linda; Salawitch, Ross J; Canty, Timothy P; Atmospheric and Oceanic Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Elevated levels of tropospheric ozone (O3) caused by emissions of NOx and VOCs negatively impact human health, crops, and ecosystems. Even if precursor emissions are reduced below current levels, predicted higher temperatures due to increased greenhouse gas emissions could impede resulting air quality benefits. Air quality models simulate the complex relationships that form O3 and are used to guide policy decisions directed at improving O3. The body of this work encompasses three projects related to improvements in the representation of O3 and precursors in air quality models. First, I examine the role of O3 and its precursors in air quality and climate change by evaluating ozone production efficiency (OPE) and O3 precursors within models. I modified a chemical mechanism and the emissions of NOx to accurately represent NOx, the reactivity of NOx with peroxy radicals, HCHO, isoprene, as well as organic and inorganic NOy reservoir species. Implementation of these modifications increased confidence in model simulations. Results indicate accepted inventories overestimated NOx emissions but underestimate total VOC reactivity and OPE. Second, I examined the dependence of surface O3 on temperature (climate penalty factor (CPF)) throughout a period of 11 years within an air quality model and measurements. Future increases in temperature could offset benefits from future reductions in the emission of O3 precursors. Determining and understanding the CPF is critical to formulating effective strategies to reduce future exceedances. I have demonstrated that the model can reproduce O3 sensitivity to temperature reasonably well. By controlling emissions specifically of NOx mankind has reduced its vulnerability. Third, I compare satellite-observed and modeled ammonia (NH3) under varying chemical environments over East Asia. Regulation of O3 precursor concentrations in the atmosphere has an indirect effect on NH3 concentrations. Air quality policy to reduce NOx and through that also nitric acid (HNO3) in the atmosphere can result in an increase in the concentration of NH3 because of its neutralizing ability. Therefore, a less acidic atmosphere sequesters less NH3. This preliminary work exposes different areas that need to be addressed to gain greater insight into NH3 emissions and chemistry.
Discerning the roles of ocean acidification, eutrophication, and river alkalization in driving long-term pH trends in the Chesapeake Bay
(2022) Guo, Yijun; Li, Ming; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Rising anthropogenic CO2 in the atmosphere and oceanic uptake of CO2 have led to a gradual decrease in seawater pH and ocean acidification, but pH changes in estuaries and coastal systems are more complicated due to a multitude of global and regional environmental drivers. Increasing global fertilizer use due to agricultural production has led to a doubling of riverine nutrient loading since the 1950s, leading to widespread eutrophication in estuarine and coastal waters. Excessive nutrient loading stimulates primary production in the surface euphotic layer, which consumes CO2 and elevates pH, but unassimilated organic matter sinks and decomposes in bottom waters, producing CO2 and reducing pH. In the meantime, human-accelerated chemical weathering, such as acid rain and mining, has resulted in rising alkalinity in many rivers and basification in estuarine and coastal waters. To discern how these environmental drivers influence long-term pH trends in coastal waters, a coupled hydrodynamic-biogeochemical-carbonate chemistry model was used to conduct hindcast simulations of the Chesapeake Bay between 1951 and 2010. The model reproduced the observed chlorophyll increase and hypoxia expansion due to the increased nutrient loading. In contrast, low-pH bottom waters and acidic volume shrank from 1950 to 1980. GAM analysis of long-term pH trends in different regions of Chesapeake Bay revealed increasing pH in the upper Bay driven by the river alkalinization, a peak pH in the mid-Bay in the 1980s coincident with the peak nutrient loading and decreasing pH in the lower Bay driven by ocean acidification. Four scenario runs were performed to assess the individual effects of rising pCO2, river alkalinization, riverine nutrient loading, and climate change (warming and sea-level rise) on long-term pH changes in the Chesapeake Bay. The model results suggested that river alkalinization was more important than ocean acidification in driving the long-term pH changes in the estuary.
QUANTIFYING THE EMISSIONS OF CARBON DIOXIDE (CO2), CARBON MONOXIDE (CO), AND NITROGEN OXIDES (NOx) FROM HUMAN ACTIVITIES: TOP-DOWN AND BOTTOM-UP APPROACHES
(2021) Ahn, Doyeon; Salawitch, Ross J.; Dickerson, Russell R.; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This dissertation encompasses three projects that quantify the emissions of greenhouse gases and air pollutants from human activities. In the first project, we use the aircraft-based mass balance (MB) approach to quantify the emission of CO2 from the Baltimore, MD-Washington, D.C. (Balt-Wash) area during winter 2015. Based on analysis of aircraft observations using the MB-based top-down approach, we estimate the emission of 1.9 ± 0.3 million metric tons (MtC) of CO2 due to the combustion of fossil fuels (FFCO2) from the Balt-Wash region February 2015. Our value is 14% lower than the 2.2 ± 0.3 MtC mean estimate of FFCO2 from four bottom-up inventories often used to drive climate policy. In the second project, we investigate the declines in the emissions of CO2 and CO from the Balt-Wash area during the COVID-19 pandemic. We estimate using the MB approach applied to aircraft data that the emission of CO2 and CO declined by 29–32% and by 27–37%, respectively, from February 2020 (prior to COVID-19 lockdowns) to April – May 2020 (in the midst of COVID-19 pandemic). We show that for February 2020, two bottom-up emission inventories (EDGARv50 and the state of Maryland inventory) underestimate CO2 emissions by 13–18%, whereas two bottom-up inventories (EDGARv50 and NEI2017) overestimate the emission of CO by 54–66%. We show that the major contributor to the overestimation of the emission of CO in the bottom-up inventory is due to the mobile (i.e., cars and trucks) sector. The third project examines the emissions of CO2 and NOx from the U.S. power sector. We quantify reductions in the emissions due to the following two factors: the direct impact of COVID-19; changes in the fuel-mix profile during 2015-2020 (i.e., switching from coal to natural gas). For the contiguous U.S., we estimate the impact of COVID-19 in April 2020 to be the decline of 18±4% on the emission of CO2 and 22± 5% on the emission of NOx. For the same month, we estimate the impact of the fuel-mix transition to be declines of 26% on the emission of CO2 and 42% on the emission of NOx.
Quantification of the Past and Future Anthropogenic Effect on Climate Change Using the Empirical Model of Global Climate, an Energy Balance Multiple Linear Regression Model
(2020) Hope, Austin Patrick; Salawitch, Ross J; Canty, Timothy P; Atmospheric and Oceanic Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The current episode of global warming is one of, if not the, biggest challenge to modern society as the world moves into the 21st century. Rising global temperatures due to anthropogenic emissions of greenhouse gases are causing sea level rise, extreme heat waves, droughts and floods, and other major social and economic disruptions. To prepare for and potentially reverse this warming trend, the causes of climate change must not only be understood, but thoroughly quantified so that we can attempt to make reasonable predictions of the future rise in global temperature and its associated consequences. The project described in this dissertation seeks to use a simple model of global climate, utilizing an energy balance and multiple linear regression approach, to provide a quantification of historical temperature trends and use that knowledge to provide probabilistic projections of future temperature. By considering many different greenhouse gas and aerosol emissions scenarios along with multiple possibilities for the role of the ocean in the climate system and the extent of climate feedbacks, I have determined that there is a 50% probability of keeping global warming beneath 2 °C if society can keep future emissions on the pathway suggested by the RCP 4.5 scenario, which includes moderately ambitious emissions reductions policies, and a 67% probability of keeping global warming beneath 1.5 °C if society can keep emissions in line with the very ambitious RCP 2.6 scenario. These probabilities are higher, e.g. more optimistic, than similar probabilities for the same scenarios given by the most recent IPCC assessment report. Similarly, we find larger carbon budgets than those from GCM analyses for any warming limitation target and confidence level, e.g. the EM-GC predicts a total carbon budget of 710 GtC for limiting global warming to 1.5 °C with 95% confidence. The results from our simple climate model suggest that the difference in future temperatures is related to an overestimation of recent warming by the IPCC global climate models. We postulate that this difference is partially due to an overestimation of cloud feedback processes in the global climate models. Importantly, though, I also reaffirm the consensus that anthropogenic emissions are driving current warming trends, and discuss both the effects of shifting the energy sector toward increase methane emissions and the timeline we have for emitting the remainder of our carbon budget – less than a decade if we wish to prevent global warming from exceeding the 1.5 °C threshold with 95% certainty.
Extreme Precipitation Projections in a Changing Climate
(2019) Hu, Huiling; Ayyub, Bilal M.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Global climate is changing at an alarming rate, with an increase in heat waves, wildfires, extreme weather events, and rising sea levels, which could cost the United States billions of dollars in lost labor, reduced crop yields, flooding, health problems, and crumbling infrastructure. Reports by hundreds of US climate scientists from 13 federal agencies in the Fourth National Climate Assessment (2018) predict that the US economy will shrink by as much as 10% by the end of the century if global warming continues with current trends. Extreme precipitation, in particular, has led to significant damage through flooding, bridge scouring, land-slides, etc.; therefore, it is critical to develop accurate and reliable methods for future extreme precipitation projection. This dissertation proposes new methods of improved projections of such extremes by appropriately accounting for a changing climate. First, this dissertation studies how to model extreme precipitation using Markov Chains and dynamic optimization. By incorporating day-to-day serial dependency and dynamic optimization, the model improves the accuracy of extreme precipitation analysis significantly. The dissertation also examines future projections of extreme precipitation. State-of-the-art methods for future precipitation projections are based on downscaled Global Climate Models (GCMs), which are not always accurate for extreme precipitation projection. This work studies accuracy when using downscaled GCMs for extreme precipitation and designed new methods based on copulas to improve the accuracy. Finally, the above methods are applied to the analysis of future trends of intensity-duration-frequency (IDF) curves, which, in turn, have extensive applications in designing drainage systems. To incorporate geographic influence on local areas, a machine-learning-based solution is proposed and validated. The results show that the gradient boosting tree can be used to accurately project future IDF curves for short durations. It is also projected that short-duration intensity will increase up to 23% for the selected representative stations in this century. In summary, this dissertation systemically studies different aspects of improvements and applications of extreme precipitation projection. By using mathematical models, such as copula and Markov Chains as well as various machine-learning models (i.e., gradient boosting tree), extreme precipitation projection can be made significantly more reliable for use.
Situational Perspectives of Maritime Piracy
(2019) Jiang, Bo; LaFree, Gary D; Criminology and Criminal Justice; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The emergence of maritime piracy has caused a great deal of concerns among various dimensions of our society. However, with few exceptions prior research has been hampered by a lack of theoretical underpinning and access to the most appropriate statistical methods. While there are nuances of piracy that can be considered quite unique, in general it can be situated within a broader framework of offending based on outcomes that seemingly share many of the same qualities. My dissertation attempts to improve our understanding of the crime by testing three core tenets of situational perspectives in the context of piracy. Three research questions motivated by LaFree and Birbeck (1991)’s conceptualization of a situation are examined – 1) To what extent does the study of maritime piracy support the central tenets of environmental criminology and crime and harm concentration at places; 2) How do offender motivation, target suitability and the absence of capable guardians and their convergence impact the instantaneous risk of piracy in South East Asia; and 3) To what extent do economic conditions of fishermen impact the instantaneous risk of piracy in East Africa and South East Asia. I rely on the IMO-GISIS database from 1995 to 2014, as well as auxiliary data from various organizations to tackle these questions. First, exploiting spatial econometrics methods, I find that there is statistically significant spatiotemporal patterns of concentration of hot spots and harm spots. Second, results from survival analyses indicate that the hazard ratios of the measures of high motivation, absence of capable guardians, suitable targets and their convergence are greater than 1 and significant in both the Malacca Strait and South China Sea. The series of robustness tests based on both frequentist and Bayesian statistics provide similar conclusions. Third, using a two-stage semiparametric approach, I find that there is statistically significant evidence to show that economic conditions of the fisherman-pirate adversely impact the instantaneous risk of ships being attacked in East Africa and the Malacca Strait and South China Sea. A robustness check based on an alternative specification supports the finding. I conclude with the implications of the research for theory, social policy and future research.

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