Nitrate management in agricultural systems is becoming increasingly important for farmers in the United States as they wrestle with the challenges of trying to increase yields per acre and decreasing their environmental impact. In the Mississippi River, the Lower Basin contributes a fraction of the nitrogen flux of that of the Upper and Central Basins. While this disparity in nitrogen flux can be attributed partly to agricultural practices such as tile drainage and the fertilizer requirements of the dominant crops in the regions, denitrification is the most likely mechanism functioning to remove nitrate (NO3-) from the system. However, in the Lower Mississippi River Basin, denitrification has not been extensively studied, and previous research has only focused on denitrification in deep groundwater. In this study, we examine the shallow surface soils in the Mississippi Delta to identify denitrification fingerprints in shallow surface soil. Using a quantitative polymerase chain reaction (qPCR), nitrate concentration measurements, and isotopic fractionation, we found strong evidence for denitrification in the shallow surface soils. High concentrations of nitrous oxide reductase (nosZ) fragments, low [NO3-] suggesting NO3- removal, isotope signatures of d15N and d18O indicative of denitrification, and trace N2O emissions all support the hypothesis that denitrification occurs in shallow surface soils in the Mississippi Delta.
Evidence from marine carbonates, evaporites, and fossil echinoderms has conclusively shown that seawater composition varied considerably during the Phanerozoic. Seawater has oscillated on 100- to 200-million-year cycles between “calcite seas,” periods with predominant carbonate formation of low-Mg calcite and Mg/Ca ratios as low as 1, and “aragonite seas,” periods with predominantly aragonite formation and Mg/Ca ratios of up to 5. Proposed explanations for the oscillations between calcite and aragonite seas include changes in the rate of Mg uptake at mid-ocean ridges and variations in shallow-water dolomitization rates. This study is the first to analyze the validity of these proposed explanations using direct measurements of seawater magnesium isotope ratios within evaporites. d26Mg values of Phanerozoic seawater were obtained by developing a new method for analysis of brine inclusions trapped within ancient marine halite. Dissolution of fluid-inclusion-rich halite followed by magnesium separation using ion chromatography and isotope ratio analysis using an MC-ICP MS led to highly reproducible d26Mg values for modern, Messinian, and Silurian-age seawater samples. Silurian and modern samples showed similar d26Mg values, suggesting that similar processes may drive seawater composition during the two time periods. Further adjustments to the methodology and additional sample analysis can achieve a more complete dataset for seawater d26Mg values and a better understanding of the processes that have controlled the chemistry of seawater throughout the Phanerozoic.
As the world rapidly urbanizes, humanity and society are also rapidly digitizing. What will the confluence of the two look like? The mass urbanization of humanity will create uniquely urban problems that policymakers must address. Of the myriad of tools which policymakers possess to address these problems, urban infrastructure stands out as one of the best. How can the digital revolution positively benefit urban infrastructure? How can it help cities connect to the information and knowledge economy? This question has spawned two potential urbanisms of the future: the Smart City and the Gigabit City.
The Smart City uses ubiquitous computing to create efficiencies in urban management. Nowhere is this more apparent than in South Korea’s u-cities, the crown jewel of which is New Songdo City. But smart cities pose numerous problems and nations may be overinvesting in their hyperbolic promises. Overall, the technologies are too nascent while the theory has left important questions about privacy, democracy, and cyber security unanswered.
The Gigabit City, on the other hand, promises economic growth through fiber to the premise (FTTP) and gigabit/second speeds. Google’s program in the Kansas City metro area has shown promises of growth to a once stagnating metro area. Policy makers can take interest as Chattanooga’s municipally funded and run fiber system has also led to economic growth. FTTP promises to make once industrial cities into gigabit cities that can connect to the knowledge economy.
These new technologies promise an urbanism of the future that can lead to overall better quality of life and let cities thrive in the current global economic order.
Changes in land uses are often cited as having great detrimental effects on biodiversity because of their negative impacts on habitat availability. Existing work in urban ecology focuses on growth and sprawl. However, the field largely overlooks deindustrializing cities, which present opportunities for conservation because of their large amounts of abandoned space. This thesis investigated the role of certain landscape variables in determining bird richness, abundance, and community composition in Duisburg, a city with a strong industrial history. Bird observations from Duisburg and the surrounding region, North Rhine-Westphalia, were used to evaluate how spatial scale affected those metrics. Four land use types and two locational factors were tested using generalized linear mixed models, concluding that the amount of natural land was most important for both richness and abundance locally. Regionally, however, the amount of urban land was the strongest predictor for richness, affecting it negatively and both urban land and natural land had inverse relationships with abundance. Not only did increasing development reduce richness locally and regionally, but it also caused biotic homogenization on both scales. Omnivores and building dwellers dominated the community in urban and industrial areas while the presence of insectivores and ground and shrub nesters decreased. Duisburg and the wider region could benefit from spatially condensing urban areas and re-greening the remaining perforated spaces, increasing richness and allowing more heterogeneity in bird communities.
Nuclear weapons have been an international reality for almost seventy years and will continue to be part of international relations for many years to come. Examination of the factors that lead states to pursue nuclear weapons is critical for successful nuclear negotiation and for preventing further proliferation. Prestige is a recognized component of nuclear decision-making, but there is little analysis of when prestige becomes a leading cause of proliferation.
This thesis contributes to prestige nuclear theory through in-depth case study analysis, the comparative testing of three theories of proliferation, and an examination of the conditions under which prestige becomes an important proliferation factor. Drawing mainly on public statements by national leaders and nuclear officials, I hypothesize that prestige becomes a prevalent nuclear justification when a state does not face an imminent security threat, when a state seeks to expand regional influence, and when a state attempts to frame national identity. Using France, Iran, and Pakistan as case studies, I compare the role of prestige to the national security and domestic politics explanations for nuclear weapons pursuit, and I test my three prestige hypotheses.
My analysis reveals prestige to be a real and prevalent factor in nuclear decision-making, and it generally supports my three prestige hypotheses. I argue that the salience of prestige in nuclear decision-making indicates the importance of maintaining a nonproliferation regime. Finally, I argue that an understanding of prestige in nuclear decision-making will help determine which nuclear negotiation strategies will be most effective.
Red (Lutjanus campechanus) and vermilion (Rhomboplites aurorubens) snapper are two of the dominant species in the northern Gulf of Mexico (GOM) reef fish complex. These two species share similar habitats and diets, but little is known about the way that they interact. It is widely believed among local fishermen that red snapper feed more aggressively than sympatric predators and competitively exclude them from both prey and baits. Thus, there is public concern that the growing red snapper stocks will negatively affect vermilion snapper as well as other species. In this thesis I (1) examined the extent of spatial and dietary overlap between red and vermilion snapper, (2) experimentally compared the feeding behavior of the two species and examined the effects of their feeding interactions, and (3) compared the catchability of the two species. Red and vermilion snapper frequently cohabited reefs in the northern GOM and their diets overlapped with marginal significance despite a lack of samples from smaller red snapper. The experiment results show that red snapper are the dominant forager of the two species, as red snapper fed at a higher rate and more successfully than vermilion snapper. These findings indicate that red and vermilion snapper do compete for prey resources and that increasing red snapper abundance could affect vermilion snapper. Lastly, comparisons of red and vermilion snapper abundance measured using video surveys and catch data revealed that red snapper are indeed more catchable than red snapper. This difference in catchability has immediate implications for catch-based stock assessments.
Sustainable biofuels can serve as an alternative to petroleum-derived transportation fuels. These synfuels can be integrated with conventional gasoline and diesel without altering current infrastructure in the transportation sector. Depending on the conversion process, biofuels can have a low or net negative carbon footprint, providing a means of reducing atmospheric carbon dioxide levels.
Pyrolysis is a thermochemical conversion pathway involving the degradation of cellulose, hemicellulose, and lignin components of biomass. Biomass pyrolysis products include non-condensable gases, condensable vapors (both hydrocarbon and aqueous), and solid char. The condensed hydrocarbon liquid, called pyrolysis-oil, is the desired product for transportation fuel production, but high oxygen content (~ 40 wt%) prevents direct use in motor vehicles. Upgrading processes can reduce oxygen levels, but in general cannot produce the high quality fuels required to replace gasoline and diesel. Advanced pyrolysis techniques, which directly integrate traditional upgrading processes into the pyrolysis reactor, on the other hand, can produce high quality transportation fuels. KiOR has recently commercialized one such pathway.
Researchers at Gas Technology Institute (GTI) have developed a particularly interesting pilot scale catalytic pyrolysis pathway, which integrates catalytic hydrotreatment with thermal pyrolysis. Process designs based around GTI’s Integrated Hydropyrolysis and Hydroconversion (IH2) pathway were evaluated to determine technical and economic feasibility of producing liquid transportation fuels. The techno- economic analyses of configurations that co-process natural gas with and without electricity generation, both yield a levelized cost of fuel of $2.41/gal. Both of these processes have significantly lower lifecycle carbon footprints than corresponding petroleum-derived fuels. Liquid fuel and electricity coproduction achieves net negative lifecycle carbon emissions per MJLHV of liquid fuel. When carbon capture and storage is added to both process designs, carbon footprint is further reduced at a cost ranging from $28-59/tCO2 avoided. Ultimately, processes modeled on GTI’s IH2 system can provide a renewable, low carbon liquid transportation fuel.
Coral recruitment and juvenile growth are essential processes for coral population maintenance and recovery, especially after disturbances such as climate change impacts, overexploitation and disease outbreaks. A growing body of research has evaluated the influence of reef microstructure on successful coral recruitment and post-settlement survival, suggesting that micro-crevices and cryptic spaces within the reef substratum enhance recruit survivorship. These studies have evaluated recruit morality from competition with macroalgae and from predation by grazing organisms, but few studies have focused specifically on early-life survival from predation by corallivorous piscine species and even fewer studies have evaluated the influence of microstructure on juvenile coral survival from corallivory. Since corals in the juvenile phase (~1-2 cm3 in size or 1-2 years old) still experience high mortality rates, there is a need to better understand the factors that facilitate successful juvenile survival. This study examined whether refugia provided by micro-crevices enhance juvenile coral survival from corallivory. Juvenile corals from two different functional groups, the slow-growing massive Porites lobata and fast-growing branching Pocillopora damicornis, were attached to experimental tiles with micro-crevices and placed on a fore-reef of Palau’s eastern reefs. Coral from both taxa had significantly higher survival rates in micro-crevices than coral in non-crevice locations. These results suggest at the importance of reef microstructure for juvenile coral survival, following early post-settlement recruitment bottlenecks. If reef microstructure is a limiting factor in this regard, it may influence the resilience and the recovery potential of coral communities by facilitating recruitment. This is an important consideration for conservation of coral reef ecosystems, as crevice abundance may be a mechanism for reef bistability.
Water scarcity is Kenya is becoming a greater concern as a result of climate change and population increase. In the Timau River Basin, a small catchment within the Upper Ewaso Ng’iro North River Basin, northwest of Mt. Kenya, substantial agricultural water use is attributed to both small-scale and commercial farms. With a relatively recent influx of immigrants to the lush mountain slopes, a highly productive region for agriculture, increased upstream water abstraction from the Timau River and others has left riverbeds to run dry in the more arid downstream areas. Commercial flower farms also use groundwater, but the resource is not significantly exploited among small-scale water users.
Data from boreholes in and around the Timau River Basin were investigated and analyzed in order to assess the hydrological characteristics of the catchment. Static water levels were used to establish a potentiometric water surface, which generally follows the contours of the land surface. Pumping logs were utilized to calculate the hydraulic properties of the aquifers. These properties, along with other characteristics of the aquifer and the regional climate, were used to create a simple groundwater flow model using MODFLOW-2005 and Groundwater Vistas.
Results from the model indicate that the region has significant potential for increased groundwater use, with maximum pumping potential nearing six times current rates. However, the model depicts some negative effects on streamflow due to greater groundwater abstraction. Thus, this study demonstrates that development of groundwater should by highly considered by water governance institutions in Kenya, though should undoubtedly involve further research.
This study analyzes the role that different aspects of liberal democratic institutions – namely, popular political accountability, civil liberties, and governmental restraint – play in accelerating the passage of policies promoting renewable energy investments, research and deployment, as well as the role they play in accelerating the expansion of renewable energy capacity and innovation directly. Using a combination of literature review, categorical data analysis, and panel data analysis, this study finds that, while theoretically, liberal democracies ought to implement and act upon more policies favorable to renewable energy investment based on the incentives they face to provide public good resources as well as their indirect capacity to foment economic growth, their actual impacts are much more nuanced.
Democratic institutions do pass a significantly greater variety of policies favorable to renewable energy investments among more stable, higher-income countries, although the comprehensiveness and stringency of these policies is difficult to determine from the data. Countries ranked highly in exhibiting governmental restraint also seem to promote a shift towards renewable energy capacity installed relative to total installed electricity capacity installed. However, political accountability and civil liberties, when controlling for other economic factors, seem to be negatively associated with a sustainable energy transition. Finally, popular political accountability is significantly associated with the passage of more Renewable Energy patents, but the relationship between civil liberties, governmental restraint, and innovation of RE technologies is weak at best. This thesis synthesizes the information provided to bring to the forefront the caveats that need to be included in the theory treating environmental policy as a public good, and provides suggestions as to the research that ought to follow this analysis.
This report presents a low-cost frequency responser analyzer (FRA) that can execute electrochemical impedance spectroscopy (EIS) at a lower cost than currently available tools. EIS is a mature, reliable and highly information-rich measurement technique that reveals numerous key properties of electrochemical systems. For decades, EIS has aided research in a myriad of fields from pharmaceuticals to fuel cells. Unfortunately, currently available EIS instrumentation costs thousands of dollars. This high cost has historically limited EIS to experimental laboratory applications. The FRA presented here, consisting of an off-the-shelf digital oscilloscope, costs less than $200.00 and therefore has potential to enable new EIS applications, as well as enormously benefit conventional applications in laboratory research. One potential new application upon which this report elaborates in detail is the balancing of battery cells in electric vehicles (EVs) to prolong battery pack lifetime, improve safety and increase EV driving range. In its current state, the proposed FRA is capable of perturbing an electrochemical system with an AC signal of prescribed frequency and amplitude and calculating the system's impedance over a range of frequencies. More work is needed to enable the FRA to perform a complete frequency sweep and calculate impedances more accurately.
Jordan is one of the most water-scarce countries on earth, but it continues to be plagued by high levels of Non-Revenue Water (NRW). I interviewed public sector and private sector officials in Jordan’s water sector to determine the causes of NRW, what is being done to reduce NRW and challenges to further NRW reduction in the future. I examined the effect of the trend towards New Public Management and privatization that has occurred in Jordan from the 1990s to the present on NRW reduction. I concluded that NRW reduction efforts in Jordan from the 1990s to the present have, on the whole, not been very successful. Moreover, in cases in which NRW reduction has been successful, this success can be attributed to external economic and societal factors, as opposed to privatization efforts themselves. I also examined the effect that further NRW reduction would have on Jordan’s parched ecosystems and on the Syrian refugee crisis. I concluded that NRW reduction could result in significant water savings, effectively generating additional water for human and ecological needs.
The interplay between gene frequencies and disease resistance has been documented in several human conditions. Hemaglobinopathies are especially well studied in humans, from sickle cell disease to alpha thalassemia. In this study, I examined the relation of gene frequency to disease resistance in the macaque malaria system. First, I examined the prevalence of Plasmodium spp. in Macaca fascicularis in Brunei, Southeast Asia, and then I looked at the genetic makeup at the alpha globin locus, which is implicated in malaria resistance. Prevalence of alpha globin variants and of malaria parasites in Brunei was compared to historical studies conducted throughout Southeast Asia. The results of this study suggest that despite the relaxation of malaria selection pressure in present-day Brunei, malaria has acted as a selective factor in macaques in the past. Additionally, a model whereby abnormal alpha globin in macaques does not confer a blood disorder disadvantage is explored. This study in M. fascicularis offers an important counterpoint to our knowledge of malaria resistance mechanisms in humans, and indicates that further investigations into non-human malaria systems are likely to provide key insights into the coevolution of hosts and their parasites.
It is important to understand how and why people adopt environmentally friendly behaviors. Environmental education promotes positive attitudes towards the environment, increased awareness of environmental issues, and, in turn, more environmentally friendly behaviors. Wildlife viewing experiences represent one means of environmental education. This study performs a direct comparison between visitors viewing animals in their natural habitat and visitors viewing animals in captivity to determine whether one method of viewing wildlife has more educational potential. I used exit surveys to assess the learning, attitude change, and behaviors of visitors at two African penguin viewing sites (one exhibited captive penguins, the other wild). I also conducted surveys at a control site that did not exhibit any animals. An all-subset modeling and model averaging approach showed that visitors’ attitudes towards conservation became significantly more positive at the two wildlife sites than at the control site. However, attitude change was not significantly different at the captive and wild animal sites. Also, neither wildlife site indicated a significantly greater potential for inspiring pro-conservation behavior changes than the control site. This demonstrates that animal experiences can effectively instill positive attitudes towards the environment, regardless of the context, but this does not necessarily result in environmentally friendly behavior.
Money is an indispensable component of bringing a vision to life in the entrepreneurship space. Indeed, 90% of startups fail primarily due to a lack of sufficient funding, according to the United States Small Business Administration. To this end, governments have the potential to influence the capital pool available to startups through financial policies such as tax incentives and grants. This paper proposes a framework for governments to understand the health of their country from an entrepreneurship perspective, specifically in the technology sector, and enact tailored policies to create an ecosystem conducive to innovation and creation substantiated by comparatively increased financial means. We
The methodology used to create this model involves regression and applied time series analyses to deduce the funding crunch area and financial policy priorities. This data is collected from publicly available investment tables on Crunchbase, press releases, and news articles, as well as results from surveys conducted by the Global Entrepreneurship Monitor. These are supplemented by qualitative data based on 30+ interviews conducted with both investors and entrepreneurs in Turkey and Jordan through collaboration with Endeavor Global. Ultimately, we present a systematic, ‘plug-and-chug’ framework for governments to customize in order to begin taking action.
In southern Italy, the region of Campania has faced challenges with waste management for decades. In addition to the problems associated with the legal waste circuit – such as waste accumulation crises in Naples, for instance – troubles arise especially from the toxic waste disposal industry, which represents a significant issue for the region. The organized crime group known as the Camorra, based in Naples and operating throughout Campania, controls the illegal toxic waste disposal activities in the region, and its involvement complicates the issue and the potential responses to it. Hazardous waste that often originates from industrial activities in northern Italy is transported into Campania, where it is disposed of in ways that disregard safety regulations and that therefore do not treat or contain the dioxins, chemicals, heavy metals, hazardous compounds, and other toxic substances included in it. Whether buried in the ground or in landfills meant for non-hazardous waste, dumped in quarries or lakes, burned, mixed with other materials and sold as things like fertilizer, falsely reclassified as non-toxic, or simply abandoned on the land, the toxic waste disposed of illegally by the Camorra pollutes the surrounding environment. Contaminants persist, accumulate, and travel throughout the ecosystem, ultimately affecting vegetation, organisms at all trophic levels, and overall ecological health. In addition to the consequences on the environment of Campania, illegal toxic waste disposal threatens the local residents. The areas of greatest known illicit disposal suffer health consequences including higher rates of cancer, congenital abnormalities, and overall mortality that correlate to toxic waste exposure. The illegal disposal operated by the Camorra thus represents an environmental crime with damaging effects on the environment and the people of the region, and addressing it will require a combination of increased regulation, international awareness, and local action.
The two policies tools most widely used to promote renewable electricity generation in the United States, the Renewable Portfolio Standard and the Feed-In Tariff, vary in the way that they impose risks and costs on society. This risk is derived from the stochasticity in the marginal cost of renewable energy. A Monte Carlo simulation is used to estimate the total social risk of each policy under different conditions in thirteen states - chosen for their renewable potential and electricity market maturity. The results show that in states with a relatively higher quality renewable resource supply, the total social risk as measured by variance if smaller under a FIT than a RPS.
The following thesis will naturally transform the Los Angeles River into yet another highway in the city. The story of the river begins and unfolds over the last 100 years, throughout which Los Angeles has constantly wrestled with an unrelenting fear of water’s presence and absence. After a 50-year storm cost the city $1.3 billion in property damage in 1938, the U.S. Army Corps of Engineers soaked the river in concrete, desperate to transform the irregular, unpredictable device into a flood channel with a highly controlled flow. Since then, theorists of urbanism in Los Angeles have struggled to comprehensively understand how the city occupies its river, making unfounded assumptions about its industrial nature. The old, foreign river has been repressed partially into the subconscious, and now, with the many renderings of revitalization that have begun to creep out of it, the city is left with a Freudian sense of the uncanny that it just cannot quite place.
By deciphering the geographical, historical, and imagined contexts of the river, this thesis tackles these uncertainties, bringing architecture into the conversation surrounding the river, and arguing that the Los Angeles River is actually crucial to understanding how the city grows and works as both an architectural and cultural construct. In order to illustrate the ways in which the river serves as a template for development in the city, the thesis broadly collects and surveys satellite images of the contemporary edge conditions that occur along the river’s 52 miles, before focusing on 8 sites along the river to detail its precise relationship to the urban fabric. These 8 sites represent the various conditions that occur along the entire length of the river, effectively sampling the river to create an accurate assessment of its unique physical and cultural urban connections. By diagramming zoning, solids, streets, and density patterns at areas including the beginning of the river at Owensmouth Avenue in Canoga Park, the equestrian bridge at the Glendale Narrows, the 1st Street bridge, and the mouth of the river at Palm Beach Park on W. Shoreline Drive in Long Beach, the thesis asserts several crucial urban implications and architectural maneuvers that result from the concretization of the river.
Having outlined the typologies of urbanism, movement, connection, and culture that surround the river for the first time, the thesis provides a comprehensive account of the effects of the history of the development of the Los Angeles River and advances potential revisions that might better serve the city at large. While the L.A. River basin is an important case to consider in and of itself, the thesis also seeks to briefly generalize some of its conclusions and strategies to apply to other urban rivers with parallel problems.
At the end of the nineteenth century, the historic center of Prague underwent its most extensive urban renewal project to date. The goal was to eliminate the former Jewish ghetto, called Josefov in honor of the emancipatory policies of Emperor Josef II. As the plans to demolish the neighborhood took shape, a demographic shift that had begun decades before was continuing: the Jewish community was leaving the old ghetto and the most impoverished Prague residents were moving in. The built environment, neglected by municipal government and landlords who lived elsewhere, fell into disrepair and its residents fell victim to disease outbreaks, floods, and fires. Despite the reality of such hazards, the campaign to demolish Josefov was characterized by anti-Semitism and xenophobia rather than concern for the health of residents and the integrity of the historic structures.
This paper explores the long history of Prague’s Jewish community, the controversies and paradoxes surrounding the plans to “end the ghetto,” and the legacy of this project as well as the present-day neighborhood that stands in place of the former ghetto. The present-day Jewish Museum, housed in the historic synagogues that survived the demolition, plays a significant role in the way that this history is understood and represented. Art, literature, and tourists’ accounts over the course of generations have influenced how visitors perceive and experience Josefov. While the architecture and infrastructure built on the grounds of the demolished ghetto bear little resemblance to what once was there, the neighborhood carries the memory and legacy of the events that took place there, historical and mythical, in a way that has proved difficult to erase.
Chrysalid is an art show exploring representations of the natural landscape through painterly abstraction. Much has been done in the humanities to understand historical, literary, and social representations of nature; my thesis introduces another voice in the fine arts. Traditional landscape painting has often depicted a romanticized landscape, filled with majestic mountains and stately pines. These representations confine ideas of nature through their scale; such paintings depict nature in its entirety, from a distance. In doing so they allow nature to be claimed by both the artist and the viewer. Chrysalid seeks to complicate this understanding of nature by depict it not as a romantic other, or even as an objective fact, but as an immersive, subjective environment. My paintings are taken from often-overlooked segments of smaller, less glamorous elements of the landscape: pigments in a rock, or bark on a felled tree. Through these miniscule images made large, I push against the viewer’s compulsion to escape through horizon lines, and complicate what a landscape is and is not. In addition to this exploration of where humans stand in relation to the environment, the show explores geographic displacement and its effects on memory. The paintings are intimately tied not only to an abstract idea of nature, but also to a specific landscape. That landscape is the Canada/Minnesota border—more specifically the Boundary Waters Canoe Area Wilderness and Quetico Provincial Park. The paintings are pulled from drawings in a notebook that traveled with me through these wildernesses, as well as from photographs taken along the way. By working and reworking these paintings in a university setting, half a country away from their origin, I try to understand how temporal and geographical distances affect my perceptions of and attitudes towards nature.
The advantages of group living in ungulates are well studied. One such advantage is that as group size increases, vigilance levels decrease; therefore, animals are able to spend more time grazing while maintaining a low predation risk. The purpose of this paper is to determine the relationship between group size and vigilance behavior in plains zebra (Equus burchelli). We also investigate if and how the zebra synchronize their vigilance behavior. Using a remote control simulated predator, we tested zebras’ response to a simulated predator and non-predator. We found that individual vigilance levels decreased as a function of group size, resulting in an increase in the proportion of time zebra spent grazing, thereby supporting previous research on ungulates. In addition, protection from predation increased with group size. We also found that redundancy did not increase with group size suggesting that the zebra are not behaving independently of each other; yet, they are also not behaving antiphonally, which is the optimal form of synchronization. In conjunction with our findings that the average distance between two alert individuals increased with group size as well as the likelihood that two alert individuals were adjacent to each other was higher than expected, we suggest that the zebra attend and respond to the actions of their nearest neighbors. Furthermore, we propose a hypothesis that individuals may not always trust the vigilance of others, double-checking on what their neighbor responds to in order to confirm there is no threat. The zebra distinguished between a potential predation attack, a simulated lion, and a nonthreatening disturbance, a simulated zorilla and monkey. The zebra detected the lion earlier than both the zorilla and monkey and also ran earlier and further from the lion as compared to the zorilla and monkey. We found no difference in vigilance behavior between the east side of the conservancy, which is frequented by tourists, and the west side of the conservancy, where tourists rarely go. We propose that tourism does not have a negative impact on the animals, but future research on the impact of tourism should be done on a finer scale than ours.
The aim of this thesis is to contribute to the existing literature that seeks to explain France and Germany’s diverging nuclear energy policies by defining the conditions under which Green Parties are successful both electorally and ideologically. As Green Parties serve as the primary political actors that push an anti-nuclear agenda within a government, a Green Party that finds success at the polls while simultaneously implementing anti-nuclear policy plays an important role in shaping a country’s outlook on nuclear energy.
To meet the goals set forth by this thesis, the text first outlines both the history of nuclear power in France and Germany and the history of each country’s Green Party. This research provides background on the unique situations each Green Party faced from their origins until present day. Based on this information, this thesis hypothesizes that strong anti-nuclear public opinion and an open political opportunity structure are individually necessary, but not individually sufficient conditions that shape the trajectories of Green Parties. Rather, the combination of these two factors creates favorable conditions for the success of Green Parties. In order to test this hypothesis, this thesis then analyzes the French and German political opportunity structures and nuclear public opinion separately, later combining the country specific results of the two explorations to provide a comprehensive view of each political situations.
The results of the data analysis support the hypothesis set forth by this thesis. The success of the German Green Party can be explained by the presence of both strong anti-nuclear public opinion as well as an open political opportunity structure. In contrast, the struggle of the French Green Party can be explained by a lack of these two conditions as the French Green Party faced both weak anti-nuclear public support and a closed political opportunity structure.
The white-lipped peccary (Tayassu pecari) is facing range-wide declines throughout the Neotropics. It has been eliminated from about 89% of its historical range in Costa Rica. Corcovado National Park, in the Osa Peninsula of Costa Rica, is the last remaining stronghold for the white-lipped peccary in the country. In 2006, 30 people were reported mining in the Park. In 2013, Corcovado National Park experienced a sudden gold rush that is attributed to the poor socioeconomic conditions of the Peninsula. The gold mining operations brought with them a wave of 250 miners and new hunting pressures on the white-lipped peccary population and the rest of the fauna in the Park. Given that the species is endangered and is susceptible to hunting due to its herding behavior and tendency to cohere and attack when threatened rather than flee, it is important to assess its probability of extinction under various hunting scenarios. Incorporating data from studies on the life history of the species throughout its range in the Neotropics and in Corcovado, I used the population viability analysis software VORTEX to simulate the population trajectories and probabilities of extinction of the species under current hunting pressures. Furthermore, I extended the model to simulate probabilities of extinction under various management scenarios where the numbers of miners hunting is reduced. The results of this study revealed that under the status quo where 250 miners are present in the Park, the population of white-lipped peccaries has a about a 40% chance of extinction within five years and about a 99% chance of extinction within 10 years. Moreover, there is an “extinction threshold” for the population between the presence of 100 and 150 miners hunting in the Park. I suggest that anti-mining and anti-poaching laws be enforced immediately, and that the number of miners be reduced to 100 at a minimum, if not completely, in order to ensure that the population of white-lipped peccaries becomes viable and evades a local extinction.
This thesis has a two-fold focus; firstly, it uses both OLS and 2SLS regressions to analyze the relationship between shale permit issuance and crude oil & natural gas prices on a county-level in Pennsylvania. Results for this section indicate that higher Brent prices and higher commercial natural gas prices encourage shale production. Secondly, I apply entity and time fixed effects regressions to explore the economic development effects that have accompanied both shale oil and shale gas production across 48 states in North America between 2000-2011. Economic development effects analyzed include: Gross County Product (GCP), median household income, poverty estimates, unemployment rate, community health by proxy of hypertension prevalence, foreclosure prevalence by proxy of Real Estate Owned (REO), and educational attainment levels. Results from these analyses suggest that shale development is either positively associated with or not associated with all examined effects except for GCP and educational attainment levels. This thesis finds a slightly positive relationship between income and shale oil and gas production across 48 states, suggesting that the Brown (2014) finding that “local employment and wage effects have been positive, but modest" (p. 21) in reference to shale gas production holds true for shale gas and shale oil production. Further, my results indicate that shale oil production is associated with lower educational attainment beyond high school. This conclusion implies that while Weber (2013) concludes that shale gas production does not harm educational attainment, analyses examining shale oil production could reach the opposite conclusion. On net, this thesis concludes that positive economic development effects have accompanied shale oil and gas production between 2000-2011 across 48 states although this boon has come, to some extent, at the cost of GCP and educational attainment.
Multiple lines of evidence indicate that the terrestrial biosphere has been a growing sink for anthropogenic carbon dioxide since the 1950s, but the nature and origin of this growth are not well understood. I investigate if the growth in the net land carbon sink (NLS) – estimated as the difference between fossil fuel emissions, the observed atmospheric growth rate, and the ocean uptake – has been abrupt or gradual by applying change point analysis. Similar to two recent studies, I identify an abrupt increase in mean NLS of 0.92-1.30 PgC/year in 1988. I add to these studies by showing that although identification of an abrupt increase in 1988 is insensitive to the choice of ocean estimate used to calculate NLS, this result is highly sensitive to the choice of statistical framework (parametric versus nonparametric).
Attempts to explain the growth in NLS have so far proven inconclusive, but much attention has focused on the carbon sink potential of Northern Eurasia, in particular, of Northern Europe. Using simulations with the Geophysical Fluid Dynamics Laboratory (GFDL) AM3/LM3 model, I find a link between declining aerosol pollution, due to the collapse of the Soviet Union and environmental regulations in Europe, and increasing regional net primary production. While this link may not explain all of the global NLS increase, an improved set of simulations with AM3/LM3 can be used to determine the historical influence of anthropogenic aerosols on the evolution of NLS.
Understanding the factors that affect leaf respiration is crucial for predicting the balance be- tween respiration and photosynthesis and for modeling carbon budget in general. Many current- day terrestrial biosphere models (TBMs) are based on the biochemical framework presented in Farquhar et al. (1980); however, empirical evidence has shown that these TBMs may be misrep- resenting leaf respiration in terms of the sensitivity to environmental factors including light and leaf expansion. Here, the notion that these factors are unimportant for carbon budget modeling is challenged. Additionally, a diurnally asymmetrical warming scenario has been incorporated to assess the impact of a changing climate on model outputs: leaf respiration, growth respira- tion, above-ground biomass, basal area, leaf area index (LAI), and transpiration. We found that depending on the model output, after about 55 simulation years, light inhibition of leaf respira- tion led to maximum changes between 12.82–27.48%, the seasonal leaf expansion modification to the model led to maximum changes between 35.86–41.37%, and the warming scenario led to changes between 53.50–90.63%. These results suggest that correctly parameterizing leaf respira- tion in terms of environmental sensitivities is, in fact, important. In general, lower leaf respiration led to increased growth and higher leaf respiration led to stunted growth. However, in the final 20 years of a simulation with light-induced inhibition of leaf respiration, forest growth decreased relative to the initial model, which had higher leaf respiration. This result, though not intuitive, was explained by light inhibition allowing for the earlier growth of relatively large trees, which have high water requirements and outcompete small trees for limited water resources.
This paper investigates the impacts of elevated atmospheric CO2 on simulated ecosystem functioning, structure, and composition. Our efforts are focused on confirming real-life experimental work via model as well as answering questions that were previously unexplored at our test site. The Duke Free-air CO2 Enrichment (FACE) site was selected as the case study site for model simulations. Fine root and nitrogen cycling dynamics were investigated, and a new model for stomatal conductance derived from H2O optimization theory is implemented into the Ecosystem Demography model version 2 (ED2). Results show that increased atmospheric CO2 increases the growth rate of both the loblolly pine and American sweetgum. Use of the stomatal conductance model also results in simulations of basal area growth rate that are more similar to observations than when a traditional, empirical stomatal conductance model is used. Also consistent with observations, the model simulated an increased standing fine root crop under elevated atmospheric CO2. The hypothesis that different allocations of carbon between roots and leaves might be more optimal at elevated atmospheric CO2 is rejected. Finally, an examination of nitrogen limitation shows that the simulated system is not increasingly nitrogen limited as a result of increased tree growth from elevated atmospheric CO2, rejecting the progressive nitrogen limitation hypothesis for the system. Still, nitrogen limitation is shown for one species, the American sweetgum. Overall, this work confirms previous experimental work at Duke FACE via improved simulation and successfully answers some previously unanswered questions from FACE scientists.
Shackleford Banks, North Carolina is a barrier island with a population of feral horses that are currently monitored by the National Park Service (NPS). The horse population has been maintained at a carrying capacity below 130 individuals to avoid problems with overgrazing on the island. Since the initial implementation of the management guidelines, the conditions of the island have changed and the forest landscape has increased. To understand how the progressions of the forest into the dune habitats and the emergence of forest in the swale habitats have affected horse behavior, I studied the vegetation and horses on Shackleford Banks. In the study, I measured characteristics of the vegetation on the island including the vegetation species, vegetation height, and vegetative state (green or brown). For the horse portion of the research, I followed 11 harems on the island examining horse behavior and acquiring coordinate locations for construction of the horses' home ranges. Since 1962, there has been a 14% increase in the amount of forest habitat and approximately 20% of the former swale area is now characterized by forest habitat. As a result, the amount of swale landscape has decreased and the remaining swales are more densely surrounded than those in the past. Additionally, the abundance of Spartina patens, a species in the horses' diets, is decreasing in the swales. The appearance of Eremochloa ophiuroides (centipede grass) in the swales is not able to nutritionally compensate for the loss in S. patens. In response, the current population of horses utilized the swales less often and decreased their grazing behavior in the more dense areas. By grazing in the dune and marsh habitats, the horses avoided the closed areas and seemed to be able to compensate for loss in nutritional content by grazing on protein-rich vegetation in the marshes and dunes.
With the global increase in introduced species, it is important to understand the contexts in which these species negatively impact ecosystems. Species introductions are particularly important in structuring island ecosystems, which have high rates of disturbance and colonization (Tilman, 1997). Through a manipulative field experiment, I examined how two introduced lizards (the predatory Leiocephalus carinatus [curly-tailed lizard] and Anolis smaragdinus [green anole]) affected the native lizard (Anolis sagrei [brown anole]) and orb- weaving spiders on small islands offshore from Staniel Cay, Bahamas. I showed that while the introduced species strongly affected brown anole height and weakly affected web spider height, they did not affect either brown anole density or web spider density. This suggests that behaviorally mediated interactions like predator avoidance are more important than consumptive interactions in structuring our island communities after the introductions. While many other studies have demonstrated the negative impacts of introduced species, in our system, the introduced species co-existed with native species without affecting population abundances (Towns, 2006; Gillespie et al, 2008).
Natural gas, particularly shale gas, comprises a growing portion of US energy production and is thought of as a bridge fuel to renewable energy. Although natural gas emits much less carbon dioxide than other fossil fuels, methane leakage may offset the climate benefits of natural gas over other fuels. I collected atmospheric measurements via a mobile, on-road sampling method near 84 natural gas sites in the Marcellus shale region in order to estimate a methane leakage rate and characterize the distribution of emitters. I determined that measurements should be collected within 300 meters of the well pad and that a single pass may not be representative. Using inverse Gaussian plume modeling, the site leakage rates ranged from 0.1 to 2800 metric tons/year. The distribution was highly skewed, with the top 6% of sites contributing 60% of methane emissions. This finding emphasizes the need to locate and repair “superemitters” to retain the climate benefits of natural gas over other fossil fuels.