Thesis (Ph. D. - Arid Lands Resource Sciences)--University of Arizona, 1997. / Includes bibliographical references (leaves 473-485).

This study was aimed at investigating the perceptions, knowledge and understanding of desertification and its causes among decision makers in northern Namibia. The focus of investigation was on desertification and its major causes as identified in the general literature, viz. deforestation, overgrazing and overcultivation. Particular attention was given to the socioeconomic and cultural factors which are behind these perceived 'ecological' causes of desertification. Furthermore, the respondents were also engaged in the generation of solutions to the problem of desertification and its causes. Data collection was based on semi-structured interviews with the regional governors, councillors and chief headmen from the four northern regions. A qualitative approach was adopted for the research and findings are essentially descriptive and qualitative. It is anticipated that the study will make an important contribution to the current debate on desertification in Namibia, specifically with regard to the perceptions, knowledge and understanding of desertification and its causes among the decision makers in northern Namibia.

The desert termite Gnathamitermes tubiformans and its unique foraging tubes are a common fixture in rangelands across Arizona, New Mexico, northern Mexico, and Texas. Although it is a native species and has thrived for millions of years, recent droughts have made its activity more visible and raised questions about its impact on vegetation. Since G. tubiformans prefers grasses as food, there has been a concern about competition between livestock and termites. Monitoring of desert termite activity was conducted through two experiments focusing on foraging distances and forager population sizes. The foraging distances experiment used circular grids in 5 m x 5 m plots to map the movement of marked G. tubiformans released from the center of the grid. Analyses showed no significant correlations between distances moved and abundance or type of vegetation. Movement of marked termites did not favor any compass directions. The second experiment used a mark-recapture estimation model to predict G. tubiformans forager populations in 5 m x 5 m plots. Linear regression analyses showed a significant positive correlation between size of the forager population and amount of total vegetation. In addition, linear regression analyses showed a significant positive correlation between total estimated number of collected termites during early recruitment and amount of vegetation cover, specifically grasses. Desertification of rangelands used by G. tubiformans and livestock is a worry with few known solutions. Elucidating answers to this problem involves ferreting out the sources of the degradation. The results of this thesis shed light on the role G. tubiformans plays in its habitat, and infer that degraded habitats with low amounts of vegetation will exhibit low termite populations.

At the 7.6 km spatial scale in which remotely-sensed satellite imagery is used in many studies of subcontinental-scale vegetation vigor and dynamics, the information acquired has yet to be fully understood and integrated with ground-level reality. This dissertation reports results and analysis from ground-truth-sampling in the arid lands of West Africa's Sudano-Sahelian zones. The geographical locations of the transects investigated were obtained from areas exhibiting steep gradients in the interannual (1980-1994) coefficients of variation (CoV) of the mean annual monthly maximum composite of the Global Area Coverage's (GAC) Normalized Difference Vegetation Index (NDV1) from the Advanced Very High Resolution Radiometer (AVHRR) series of satellites. I begin this work by disaggregating the term "food security" into its various components, then continue by exploring what is generally understood by the concept of "desertification" and what this actually translates to in terms of land degradation. I then discuss how an error in NASA's method for calculating interannual NDVI CoVs impacted both my own work and our concepts of the Sahel's boundaries. Field data I gathered in the central and northern Sahel indicate that cogent, simple explanations of latitudinal variations in CoV do exist, albeit not everywhere. The Gourma region of Mali provides an excellent example of how complexity confounds any neat quantization of information. For the more southerly agropastoral zone, high CoV variability flags rapid, dynamic desertification processes. Results of village- and household-level profiles along a transect in the heart of Hausaland confirm that rapid, dynamic land degradation corresponds with a high interannual CoV. Climate, especially rainfall and potential evaporation, form the basis of an analysis the outcome of which explains how and why the Malian Gourma shows a nonlinear, "anomalous" NDVI response to rainfall. I also explore the strong correlation between rainfall and NDVI in the southern Sahel, but conclude that if there is a link between NDVI and crop yields, it is very weak indeed. Finally, my research highlights several policy measures that may retard desertification and enhance food security.

Thesis (Ph.D.)--George Mason University, 2009. / Vita: p. 287. Thesis co-directors: Sheryl L. Beach, Guido Cervone. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Earth Systems and Geoinformation Sciences. Title from PDF t.p. (viewed Oct. 11, 2009). Includes bibliographical references (p. 267-286). Also issued in print.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Ecosystem degradation in Iceland has been severe since man arrived 1100 years ago. Birch woodlands cover has declined from 25% of the land area, to only 1%. The deforestation is considered to be the initial stage in the land degradation process, followed by surface destabilization, and later erosion. The objective of this study was to quantify and evaluate factors that contribute to the early stages of land degradation in Icelandic ecosystems. Specific objectives were to improve our understanding of how livestock grazing might initiate early degradation stages, elucidate field-based landscape metrics useful for characterizing degradation stages, and to determine if landscape metrics obtained from remote sensing data can be used to detect landscape structure changes and identify degraded and at risk rangelands in real time over extensive and remote areas. A State-and-Transition conceptual model was constructed for the experimental area to identify potential key processes in the degradation sequence, and to formalize research questions. Experimental plots were established in five plant community types representing a space-for-time degradation sequence. Birch seedling (Betula pubescens Ehrh.) growth and survival was reduced with repeated clipping treatment applied to simulate browsing, but the amount of decline varied with plant community type. This suggests that continuous grazing may contribute to deforestation, as regeneration will be reduced over time. Intense grazing treatments, simulating both grazing and trampling, increased surface instability and soil loss compared to grazing only or control, suggesting that intense grazing may contribute to surface destabilization and therefore to land degradation. Erosion appeared to be active in the most intense treatments, also within the woodlands. The data indicate that the woodlands may have lower resilience than the other plant communities as treatment effects appeared quicker there. The woodlands may thus be particularly vulnerable to intense grazing. The landscape metrics used to quantify changes in landscape surface properties over a 51 year period yielded inconclusive results, either because of data limitations or because of non-detectable erosion activity. The results do generally support the proposed S&T model for the experimental area. It is concluded that grazing may contribute to woodland decline, and intensify degradation processes.

No description available.

This study documented the decline of the forests of the Petra Region of Jordan, as represented at Sidd al-Ahmar, within the Petra Archaeological Park. Biogeographical and anthropological methods were employed to explore the history of the forests. Archaeology and historical narratives provided a portrait of the study area from prehistory to the early 20th century. Aerial surveys from 1924 and 2002 were analyzed to quantify changes in forest cover. Mapping and inventory of indicator species measured short-term change between 2003 and 2006. Interviews, field observation and participant observation in the tourist industry provided a socio-cultural context for quantitative analysis and for recommendations for remediation of pressures on the remaining forest. The research documents a 58% decline in tree cover between 1924-2002, and a decline of 4.23% between 2003-2006. The conclusions question concepts such as "landscape integrity" and the usefulness of non-interventionist ideology in an historic and rapidly changing region.

No description available.