College of Behavioral & Social Sciences

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    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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    Fire Dynamics and Woody Cover Changes in the Serengeti-Mara Ecosystem 2000 to 2005 - A Remote Sensing Approach
    (2007-01-21) Dempewolf, Jan; DeFries, Ruth; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The Serengeti-Mara savanna environment in East Africa is characterized by changing levels of woody cover and a dynamic fire regime. The relative proportion of woodland to grassland savanna affects animal habitat, biodiversity, and carbon storage, and is regulated by factors such as the fire regime (frequency, intensity, seasonality), and precipitation. The main objectives of this dissertation are to determine recent changes in woody cover at a regional scale and identify fire regimes and climate associated with these changes. Understanding these relationships is important for the assessment of future trajectories of woody cover under changing climate. Required spatially coherent data layers can only be obtained at the regional scale through the analysis of remote sensing data. Woody cover changes between 2000 and 2005 were derived from field data and a time series of MODIS satellite imagery at 500 m spatial resolution. Data layers on the controlling variables (fire frequency, seasonality, intensity and rainfall) were developed using a combination of remote sensing and model-based approaches. Burned areas were mapped using daily MODIS imagery at 250 m resolution. Outputs were used to make the requisite layers depicting fire frequency and seasonality. Fire intensity was derived using a model based on empirical relationships, mainly estimating fire fuel load as a function of rainfall and grazing. The combined data layers were analyzed using regression and decision tree techniques. Results suggest woody cover in central and northern Serengeti National Park continued to increase after 2000. Woody cover decreases were strongest in the wider Maswa Game Reserve area (MSW) under low precipitation conditions and late season burning. Woody cover losses in burned areas were also higher in the low fire frequency region of the Maasai Mara National Reserve (MNR). Fire seasonality was the most important fire regime parameter controlling woody cover in burned woodland savanna areas while fire intensity was most relevant for grassland savanna areas. Continued late season burning in drought years might cause further decrease of woody cover in MSW. MNR is expected to continue to be dominated by grassland savanna at similar fire frequency and browsing levels.