College of Behavioral & Social Sciences
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations..
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Item DYNAMICS OF GLOBAL SURFACE WATER 1999 - PRESENT(2021) Pickens, Amy; Hansen, Matthew C; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Inland surface waters are critical to life, supplying fresh water and habitat, but are constantly in flux. There have been considerable advances in surface water monitoring over the last decade, though the extent of surface water has not been well-quantified per international reporting standards. Global characterizations of change have been primarily bi-temporal. This is problematic due to significant areas with multi-year cycles of wet and dry periods or anomalous high water or drought years. Many areas also exhibit strong seasonal fluctuations, such as floodplains and other natural wetlands. This dissertation aims to characterize open surface water extent dynamics by employing all of the Landsat archive 1999-present, and to report area estimates with associated uncertainty measures as required by policy guidelines. From 1999 to 2018, the extent of permanent water (in liquid or ice state) was 2.93 (standard error ±0.09) million km2, representing only 60.82 (±1.93)% of the total area that had water for some duration of the period. The unidirectional loss and gain areas were relatively small, accounting for only 1.10 (±0.23)% and 2.87 (±0.58)% of total water area, respectively. The area that transitioned multiple times between water and land states on an annual scale was over four times larger (19.74 (±2.16)%), totaling 0.95 (±0.10) million km2, establishing the need to evaluate the time-series from the entire period to assess change dynamics. From a seasonal perspective, June has over double the amount of open surface water as January, with 3.91 (±0.19) million km2 and 1.59 (±0.21) million km2, respectively. This is due to the vast network of lakes and rivers across the high-latitudes of the northern hemisphere that freeze over during the winter, with a maximum extent of ice over areas of permanent and seasonal water in February, totaling 2.49 (±0.25) million km2. This is the first global study to estimate the areas of extent and change with associated uncertainty measures and evaluate the seasonal dynamics of surface water and ice in a combined analysis. The methods developed here provide a framework for continuing to evaluate past trends and monitoring current dynamics of surface water and ice.Item Improved quantification of forest cover change and implications for the carbon cycle(2015) Song, Xiaopeng; Townshend, John R; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Changes in forest cover significantly affect the global carbon cycle, the hydrological cycle and biodiversity richness. This dissertation explores the potential of satellite-derived land cover datasets in quantifying changes in global forest cover and carbon stock. The research involved the following three components: 1) improving forest cover characterization, 2) developing advanced methods for detecting forest cover change (FCC) and 3) estimating the amount and trend of forest carbon change. The first component sought to improve global forest cover characterization through data fusion. Multiple global land cover maps have been generated, which collectively represent our current best knowledge of global land cover, but substantial discrepancies were found in their depiction of forest. I demonstrated that the extent and density of forest cover could be much better characterized by integrating existing datasets. However, these independent map products cannot be directly compared to quantify FCC, because post-classification change detection requires significant consistency in land cover definition, satellite data source and classification procedure. The yearly vegetation continuous field (VCF) product derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) provides a prototype that fulfills such requirement. The second component was intended to explore the features of this time series dataset in change analysis. A new algorithm called VCF-based Change Analysis was developed that can explicitly characterize the timing and intensity of FCC. The efficiency and robustness of this algorithm stem from two realistic assumptions—the spatial rarity and the temporal continuity of land cover change/modification. The developed method was applied to continental scales for mapping forest disturbance hotspots. The third component of the research combined MODIS-based deforestation indicators, a Landsat sample and a biomass dataset to estimate annual carbon emissions from deforestation with a regional focus on the Amazon basin. I found that deforestation emissions varied considerably not only across regions but also from year to year. Moreover, deforestation has been progressively encroaching into higher biomass lands in the Amazon interior. These observed deforestation and emission dynamics are expected to provide scientific support to policies on reducing emissions from deforestation and forest degradation (REDD+). The generated panel data are also of great value for evaluating forest protection policies.Item Activist Globalization: How Markets, Societies and States Empower Cause-Oriented Action in Transnational Relations(2011) Pinto, Rodrigo G.; Conca, Ken; Government and Politics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study examines how transnational conditions of markets, societies and states empower civic groups, social movements, advocacy networks or resisters to participate in cause-oriented action that connects two or more polities. Preliminary theses infatuated with the latest and thickest wave of globalization have blown back into a solidified antithesis. Under this influential antithesis, international interactions between states create more opportunities for transnational activism than do global flows between societies or markets. The evidence analyzed here suggests a refutation of that prevalent antithesis. Instead, it supports the synthesizing hypothesis of this study: The more markets and societies globalize and the more states interact, the more transnational activism occurs. The research conducted here develops on a promising explanatory typology that is the best attempt to answer the main question about activism in international relations (IR) studies at present. This dissertation builds on such theory, moderating short-range and statist imbalances in conventional IR and cross-national (comparative) research on the consequences of interstate regimes and political opportunity structures, respectively. The study goes on to make this prior scholarship more accurate, comprehensive and reflective. First, tests of the prime theory over a longer history, which predates 1945, here elevate globalism toward a favorable condition that is as consequential as internationalism for activism across borders. Second, this study conceptualizes four explanatory processes--or chains of causal mechanisms--that link activism mainly to encouragement from globalization. These original models expose a grand, causal theory to have outpaced its necessary processual, mechanismic bases. Finally, the study addresses the spatial transnationality and transnationalization of activism. It extends the typology of explanatory processes to distinguish the primary scale of activist actions from the locus of activist causes, along a domestic-foreign frontier. The extension renders as unexamined a conventional assumption that activism transnationalizes through a one-dimensional globalization from local toward global proportions. The dissertation uses qualitative, case-study and process-tracing, methods to compare and generalize beyond two transnational activist campaigns. These campaigns are situated temporally from the 1860s to the 1950s, geographically through inclusion of actors based in Brazil, and thematically via incorporation of biodiversity in activist deed or discourse.