Using GIS and remote sensing to evaluate past rangeland management efforts.
This brief highlights how a critical GIS analysis of past conditions can shine a light on better range management decisions with respect to woody vegetation overgrowth. For over 100 years, drought, lack of natural fire, and, in some cases, unmanaged grazing have combined to create conditions where mesquite and other woody species outcompete native grasses in the Altar Valley (south-central Pima County). The subsequent decline in native grasses caused a less productive environment and soil more prone to erosion. The 10,000 acre Elkhorn Ranch in the foothills of the Baboquivari Mountains have been managing mesquite and other woody vegetation for almost 35 years. A GIS and aerial photographic analysis of the ranch's efforts to reduce mesquite and other woody vegetation include orthomosaic combination of historic single frame aerial photos; vegetation classification of aerial datasets from 1972, 1993, 2003, 2007, 2010, 2013, 2015, and 2017; critical analysis of the accuracy of those classified datasets; density and change analysis; correlating change with management efforts; and finally, the development of an online story map to showcase the effectiveness of the ranch's efforts to other ranchers and the greater conservation community.