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Urban ecosystems cover less than 3% of the Earth's land surface, yet more than half of the human population lives in urban areas. The process of urbanization stresses biodiversity and other ecosystem functions within and far beyond the city. To understand the mechanisms underlying observed changes in biodiversity patterns, several

Urban ecosystems cover less than 3% of the Earth's land surface, yet more than half of the human population lives in urban areas. The process of urbanization stresses biodiversity and other ecosystem functions within and far beyond the city. To understand the mechanisms underlying observed changes in biodiversity patterns, several observational and experimental studies were performed in the metropolitan area of Phoenix, Arizona, and the surrounding Sonoran Desert. The first study was comprised of seven years of arthropod monitoring using pitfall traps in common urban land-use types. This study revealed differences in community structure, diversity and abundance over time and between urban and wildland habitats. Urban habitats with high productivity had higher abundances of arthropods, but lower diversity compared to wildland habitats. Arthropod abundance in less-productive urban habitats was positively correlated with precipitation, but abundance in high-productivity urban habitats was completely decoupled from annual fluctuations in precipitation. This study showed the buffering capacity and the habitat heterogeneity of urban areas. To test the mechanisms controlling community diversity and structure in urban areas, a major field experiment was initiated. Productivity of the native shrub Encelia farinosa and bird predation of associated arthropods were manipulated to test whether bottom-up or top-down forces were more important in urban habitats compared to wildland habitats. Abundance, richness and similarity were monitored, revealing clear differences between urban and wildland habitats. An unusually cold and dry first season had a negative effect on plant growth and arthropod abundance. Plants in urban habitats were relatively unaffected by the low temperature. An increase in arthropod abundance with water availability indicated bottom-up forces in wildland habitats, whereas results from bird exclusions suggested that bird predation may not be as prominent in cities as previously thought. In contrast to the pitfall study, arthropod abundance was lower in urban habitats. A second field experiment testing the sheltering effect of urban structures demonstrated that reduced wind speed is an important factor facilitating plant growth in urban areas. A mathematical model incorporating wind, water and temperature demonstrated that urban habitats may be more robust than wildland habitats, supporting the empirical results.

ContributorsBang, Christofer (Author) / Faeth, Stanley H. (Thesis advisor) / Sabo, John L. (Thesis advisor) / Grimm, Nancy (Committee member) / Anderies, J. Marty (Committee member) / Warren, Paige S. (Committee member) / Arizona State University (Publisher)
Created2010
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Urban Heat Island (UHI) is considered as one of the major problems in the 21st century posed to human beings as a result of urbanization and industrialization of human civilization. The large amount of heat generated from urban structures, as they consume and re-radiate solar radiations, and from the anthropogenic

Urban Heat Island (UHI) is considered as one of the major problems in the 21st century posed to human beings as a result of urbanization and industrialization of human civilization. The large amount of heat generated from urban structures, as they consume and re-radiate solar radiations, and from the anthropogenic heat sources are the main causes of UHI. The two heat sources increase the temperatures of an urban area as compared to its surroundings, which is known as Urban Heat Island Intensity (UHII). The problem is even worse in cities or metropolises with large population and extensive economic activities. The estimated three billion people living in the urban areas in the world are directly exposed to the problem, which will be increased significantly in the near future. Due to the severity of the problem, vast research effort has been dedicated and a wide range of literature is available for the subject. The literature available in this area includes the latest research approaches, concepts, methodologies, latest investigation tools and mitigation measures. This study was carried out to review and summarize this research area through an investigation of the most important feature of UHI. It was concluded that the heat re-radiated by the urban structures plays the most important role which should be investigated in details to study urban heating especially the UHI. It was also concluded that the future research should be focused on design and planning parameters for reducing the effects of urban heat island and ultimately living in a better environment.

ContributorsRizwan, Ahmed Memon (Author) / Dennis, Leung Y.C. (Author) / Liu, Chunho (Author)
Created2007-09-27
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Urbanization is a primary driver of ecological change and occurs across a gradient from low- to high- density development. Wildlife species can exhibit different responses to urbanization, with some species being more sensitive than others. Further, wildlife communities can exhibit varying patterns of species richness across the gradient of urbanization,

Urbanization is a primary driver of ecological change and occurs across a gradient from low- to high- density development. Wildlife species can exhibit different responses to urbanization, with some species being more sensitive than others. Further, wildlife communities can exhibit varying patterns of species richness across the gradient of urbanization, where species richness can either decrease linearly or peak at intermediate levels of urbanization, consistent with the intermediate disturbance hypothesis (IDH). For chapter one, the objective was to evaluate the response of bats to urbanization across seasons. It was predicted that bat species would exhibit different responses to urbanization and that bats would increase use of urbanized areas in the summer season, where food and water resources were assumed to be greater. For chapter two, the objective was to evaluate species richness of bats across the gradient of urbanization in the summer season. Species richness of bats was predicted to either decrease linearly or peak at moderate levels of urban intensity. To test these hypotheses, 50 sites across the gradient of urbanization were sampled during four seasons using stationary acoustic bat monitors. Fourteen bat species were identified during 1000 nightly occasions. Consistent with chapter one predictions, bat species exhibited different responses to urbanization, with most bats being sensitive to urbanization. Counter to predictions, most bats did not appear to shift their response to urbanization across seasons. However, two bats (i.e., big brown bat and Yuma myotis) exhibited higher use of urbanized areas in the summer compared to other seasons. Consistent with chapter two predictions, species richness of bats decreased with increasing urban intensity. Results from this study demonstrate that most bats in the community were sensitive to urbanization, which is potentially related to species traits and has important conservation implications. First, it is likely important to maintain high-quality undeveloped habitat with low anthropogenic disturbance in wildland areas for species that are sensitive to urbanization and to maximize species richness. In addition, for bats that are tolerant of urbanization and to increase species richness in urbanized areas, it is likely important to preserve resources in urbanized areas and increase landscape connectivity.
ContributorsDwyer, Jessie (Author) / Lewis, Jesse S (Thesis advisor) / Moore, Marianne S (Committee member) / Saul, Steven E (Committee member) / Arizona State University (Publisher)
Created2021
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Description
The built environment increases radiant heat exchange in urban areas by several degrees hotter compared to non-urban areas. Research has investigated how urbanization and heat affect human health; but there is scant literature on the effects of urban heat on wildlife. Animal body condition can be used to assess overall

The built environment increases radiant heat exchange in urban areas by several degrees hotter compared to non-urban areas. Research has investigated how urbanization and heat affect human health; but there is scant literature on the effects of urban heat on wildlife. Animal body condition can be used to assess overall health. This parameter estimates the storage of energy-rich fat, which is important for growth, survival, and reproduction. The purpose of my research was to examine the Urban Heat Island effect on wild rodents across urban field sites spanning three strata of land surface temperature. Site level surface temperatures were measured using temperature data loggers and I captured 116 adult pocket mice (Chaetodipus spp. and Perognathus spp.) and Merriam’s kangaroo rats (Dipodomys merriami) to measure their body condition using accurate and noninvasive quantitative magnetic resonance. I used baited Sherman live traps from mid-May to early September during 2019 and 2020 in mountainous urban parks and open spaces over two summers. Rodents were captured at seven sites near the Phoenix metropolitan area; an ideal area for examining the effect of extreme heat experienced by urban wildlife. Results supported the prediction that rodent body condition was greatest in the cooler temperature stratas compared to the hottest temperature strata. I related rodent body condition to environmental predictors to dispute to environmental predictors to dispute alternative hypotheses; such as vegetation cover and degree of urbanization. Results based on measures of body fat and environmental predictors show pocket mice have more fat where vegetation is higher, nighttime temperatures are lower, surface temperatures are lower, and urbanization is greater. Kangaroo rats have more fat where surface temperature is lower. My results contribute to understanding the negative effects of extreme heat on body condition and generalized health experienced by urban wildlife because of the built environment. This research shows a need to investigate further impacts of urban heat on wildlife. Management suggestions for urban parks and open spaces include increasing vegetation cover, reducing impervious surface, and building with materials that reduce radiant heat.
ContributorsAllen, Brittany D'Ann (Author) / Bateman, Heather L (Thesis advisor) / Moore, Marianne S (Committee member) / Hondula, David M (Committee member) / Arizona State University (Publisher)
Created2021