Many National Forests in the United States are under substantial pressure from increasing human development and demand. Impacts of recreational trail users on surrounding ecosystems and watersheds significantly affect areas where trail systems are not thoroughly planned and maintained. These impacts can degrade ecosystems and watersheds and may include the following: noise pollution, erosion/geomorphic impacts, weed invasion, increased travel into virgin areas, water/soil pollution and decreased biodiversity near trails. Based on a network of existing trails located within the San Bernardino National Forest near Big Bear Lake, California, this research is provided as a case study to develop a tool to assesses the impacts of recreational trails to surrounding ecology and geomorphology. The results of this study minimize the need for field-based surveys and data that can often be impractical, time intensive, expensive, and inconsistent due to variability in personnel experience, objective analysis, and training. A simple Geographic Information System (GIS) based spatial analysis is developed to predict high impact trail segments without field-based information. In turn the efficiency and accuracy of management and implementation of trail systems can be increased. A combination of locally and regionally available endangered or sensitive species habitat locations, elevation models, soil types, and trail spatial data is utilized to determine the relative impact of each trail within a small sub system of trails. Calibration and validation of the GIS-predicted impacts is performed utilizing two field surveys. The GIS-developed model has a positive correlation (calibration R2=0.93, validation R2=0.87) with relatively low Root Mean Square Errors (≤ 10% of the sample size) for determining the location of highly impacted trails based on two sample areas. The methods developed can be applied to analyze the ecosystem impacts of existing and proposed trail systems not only in the San Bernardino National Forest, but also for a variety of land covers, geomorphic characteristics, regions, climates, and recreation types.