Impact Of Suburbs: Assessing Tree Coverage Using Geo-spatial Tools In The City Of Fort Worth
Yorek, James Colton
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Throughout the last century, developers kept pace with the growing housing demand, and in doing so, former rural landscape continued to become part of the urban fabric (Corrigan et al, 2004; Secker 2007). This newly acquired land is primarily being shaped by development typically in the form of single-family residential subdivisions (Berger, 2006). With the increasing consumption of land for development there are increasing concerns from the public surrounding issues of land use changes, natural resources, and the protection of land through conservation efforts (Johnston et al, 2006). One of these issues is the acceptance of the urban forest as a major asset "that can contribute to reduced energy use, a smaller carbon footprint, and a more livable region" (VNT, 2008, 8).The purpose of this research is to assess the impact of suburban development on tree coverage in order to understand and address the issues surrounding natural resources in urbanized areas. This is addressed by analyzing changes that have taken place with the tree canopy, primarily in the city of Fort Worth's suburbs within the past two decades. Three primary research questions were proposed in order to address development related impact issues while exploring geo-spatial tools and methods that could be suitable for such an investigation on a broader scale. 1) How do subdivisions impact tree coverage within the city of Fort Worth's suburbs? 2) What are the changes in tree coverage in the city of Fort Worth within the past two decades? 3) What geo-spatial methods are available and/or suitable for North Texas to assess changes in tree coverage?The city of Fort Worth and its suburbs was chosen as the study area due to the variety of environmental settings contained within the city limits ranging from urban to rural. Additionally, analyzing an area governed by a common set of ordinances dismisses possible unknown variables related design requirements set forth by the city when making comparisons. The study uses Geographic Information Systems (GIS) and the associated data as the means of analysis. Datasets attained from secondary sources were used for the research. This data includes but is not limited to: city limit boundaries, water bodies, highways, and orthoimagery. A few common methods of analyzing tree coverage were addressed and tested on a small scale for accuracy, efficiency, and applicability such as orthoimagery conversion techniques outlined in Morrow (Morrow, 2001). Then a methodology was adopted based on the strengths of the known methods and further developed isolating tree canopy using spectral band 5 from the 1990 and 2005 Global Land Survey (GLS) derived from Landsat 5 and 7 TM. City annexation, subdivision parcels, and land use data were used as boundaries in order to extract tree canopy area for analysis and comparison.Findings from the analysis indicate that subdivisions in the city of Fort Worth have substantially impacted tree coverage when compared to the same land in a pre-development era. In addition, the comparison of Fort Worth's urban and suburban environments shows that in 2005, the tree canopy coverage was of a higher percentage in the urban setting. Moreover, the methods adopted and further developed for this research seemed to provide easily adoptable, relatively accurate, time and cost efficient results, yet to remain proven by statistical means with further research.In conclusion the method developed and findings assessed through this research can be used for landscape planning decisions in the city of Fort Worth and aid in environmental assessment in urbanized areas. Additionally, they elicit the need for further research in development related impact issues on the surrounding natural resources.