Geographic Analysis of Current and Historical Vegetation of East Texas

This study uses two sources of secondary data to compare vegetation communities in East Texas and analyze how they have changed in the past eight decades. The first data source is a hand-drawn timber survey map generated by the U.S. Department of Agriculture circa 1935. The second data source is the Texas Parks and Wildlife Department’s Ecological Mapping Systems of Texas (EMS-T) finished in 2014. A third data source is used to crosswalk between the two principal sources. Using digital mapping techniques, classification boundaries of the historic map were digitized creating an overall area of interest. This was used to extract attribute data from the second data source creating a data extent defined by the digitized boundaries of the 1935 map. Although identical, their resulting attribute data contained no mechanism for a data join. The third data source, McMahon’s The Vegetation Types of Texas, Including Cropland provided this attribute bridge. This study found that 2.49% of the overall area has been converted to urban use. This shift in land use underscores an overall rise in population, which, in turn, drives the need for natural resources and conversion of ecosystems to other land uses. For example, 34% of the ’Shortleaf, Loblolly, Hardwood’ classification is now exclusively devoted to timber production. In the ‘Bottomland Hardwood’ classification, reservoirs now account for 13% of its total area. Today only 0.07% of the 1935 longleaf pine extent is exclusively longleaf pine and 56% of areas that once were longleaf pine are now pine plantation. Areas of urban growth have had the greatest impact on the ‘Loblolly, Hardwood’ classification where 10.3% has been converted to urban cover. Invasive species are evident as well. For example, of the ‘Loblolly, Hardwood’ classification, 3.7% is now invasive Chinese Tallow (Triadica sebifera). The resulting analysis allows for comparisons based on “Common Name” attributes, LU/LC value, and associated area values. Beneficially, such comparison allows for general assumptions about environmental impact and provides an analytical mechanism by which to mitigate future loss due to human or natural influences.