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 Sample-Based Estimation of Tree Cover Change in Haiti Using Aerial Photography: Substantial Increase in Tree Cover between 2002 and 2010(MDPI, 2021-09-14) Rodrigues-Eklund, Gabriela; Hansen, Matthew C.; Tyukavina, Alexandra; Stehman, Stephen V.; Hubacek, Klaus; Baiocchi, GiovanniRecent studies have used high resolution imagery to estimate tree cover and changes in natural forest cover in Haiti. However, there is still no rigorous quantification of tree cover change accounting for planted or managed trees, which are very important in Haiti’s farming systems. We estimated net tree cover change, gross loss, and gross gain in Haiti between 2002 and 2010 from a stratified random sample of 400 pixels with a systematic sub-sample of 25 points. Using 30 cm and 1 m resolution images, we classified land cover at each point, with any point touching a woody plant higher than 5 m classified as tree crown. We found a net increase in tree crown cover equivalent to 5.0 ± 2.3% (95% confidence interval) of Haiti’s land area. Gross gains and losses amounted to 9.0 ± 2.1% and 4.0 ± 1.3% of the territory, respectively. These results challenge, for the first time with empirical evidence, the predominant narrative that portrays Haiti as experiencing ongoing forest or tree cover loss. The net gain in tree cover quantified here represents a 35% increase from 2002 to 2010. Further research is needed to determine the drivers of this substantial net gain in tree cover at the national scale.Item Land-cover and land-use change trajectory hopping facilitates estate-crop expansion into protected forests in Indonesia(Wiley, 2023-05-10) Xin, Yu; Sun, Laixiang; Hansen, Matthew C.Protected areas (PAs) have been regarded as a critical strategy to protect natural forest (NF) and biodiversity. Estate-crop expansion is an important driver of deforestation in Indonesia. Yet, little is known regarding the temporal dynamics of PA effectiveness in preventing estate-crop expansion into NF. We employ Cox proportional hazard models and their extensions to characterize the dynamics of estate-crop expansion into NF in Indonesia during 1996–2015. The results show that PA effectiveness in Sumatra decreased over time and became insignificant in 2012–2015. A multistate modeling analysis shows that hopping in land-cover and land-use change (LCLUC) trajectories with shrub and/or bare ground as intermediates has decreased PA effectiveness and facilitated the expansion. Preventing LCLUC trajectory hopping becomes crucial to biodiversity conservation because it tends to occur at lowland forest, diminishing natural habitat area and increasing NF isolation.Item Changes in Amazon Forest Structure from Land-Use Fires: Integrating Satellite Remote Sensing and Ecosystem Modeling(2008-11-17) Morton, Douglas; DeFries, Ruth S; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Fire is the dominant method of deforestation and agricultural maintenance in Amazonia, and these land-use fires frequently escape their intended boundaries and burn into adjacent forests. Initial understory fires may increase forest flammability, thereby creating a positive fire feedback and the potential for long-term changes in Amazon forest structure. The four studies in this dissertation describe the development and integration of satellite remote sensing and ecosystem modeling approaches to characterize land-use fires and their consequences in southern Amazon forests. The dissertation contributes three new methods: use of the local frequency of satellite-based active fire detections to distinguish between deforestation and maintenance fires, use of satellite data time series to identify canopy damage from understory fires, and development of a height-structured fire sub-model in Ecosystem Demography, an advanced ecosystem model, to evaluate the impacts of a positive fire feedback on forest structure and composition. Conclusions from the dissertation demonstrate that the expansion of mechanized agricultural production in southern Amazonia increased the frequency and duration of fire use compared to less intensive methods of deforestation for pasture. Based on this increase in the frequency of land-use fires, fire emissions from current deforestation may be higher than estimated for previous decades. Canopy damage from understory fires was widespread in both dry and wet years, suggesting that drought conditions may not be necessary to burn extensive areas of southern Amazon forests. Understory fires were five times more common in previously-burned than unburned forest, providing satellite-based evidence for a positive fire feedback in southern Amazonia. The impact of this positive fire feedback on forest structure and composition was assessed using the Ecosystem Demography model. Scenarios of continued understory fires under current climate conditions show the potential to trap forests in a fire-prone structure dominated by early-successional trees, similar to secondary forests, reducing net carbon storage by 20-46% within 100 years. In summary, satellite and model-based results from the dissertation demonstrate that fire-damaged forests are an extensive and long-term component of the frontier landscape in southern Amazonia and suggest that a positive fire feedback could maintain long-term changes in forest structure and composition in the region.Item HISTORICAL AND COMPUTATIONAL ANALYSIS OF LONG-TERM ENVIRONMENTAL CHANGE: FORESTS IN THE SHENANDOAH VALLEY OF VIRGINIA(2005-08-01) Wilson, James W.; Geores, Martha E; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The increase and decrease of forests is a major factor of land cover change. This study of forest change in the Shenandoah Valley builds upon the rich historiography of the region through the analysis of generalized and spatially explicit primary and secondary sources covering the period of 1700 to 2000. Combining geo-historical and geo-computational approaches produced a more robust picture of land cover change than would be possible using only one method. Comparing modern and historical reports on the timing of forest clearance and re-growth revealed that a discrepancy existed between the spatially explicit sources and existing historical interpretations regarding the timing and location of forest clearance and re-growth. Understanding this discrepancy is important for the interpretation of forest change and its implications in the Shenandoah Valley and beyond. Two main aspects of the study are the thorough interrogation and comparison of different data sources, and the subsequent analysis and interpretation of the data. Historic maps (1864, 1906, and c. 1945) and digital data sets derived from remotely sensed images (c. 1974 and c. 1992) were analyzed in a geographic information system (GIS) and compared to agricultural census data and published reports of land use and land cover change. Three major findings came out of this study. First, the spatially explicit sources produced values for the amount of cleared area that were within 0.5 to 2.7% of the same information derived from the agricultural census. Second, the maximum amount of forest clearance occurred 25 - 50 years later than existing published reports indicated. Third, the commonly held explanations of federal land acquisition and the abandonment of farms on steep slopes did not account for the observed patterns of forest re-growth. The documented variations in spatial and temporal patterns and reasons for the variations have impacts on our understanding of cultural and physical processes that took place in the region.