Karst environments are unique landscapes that contain important resources, including freshwater aquifers and specialized ecosystems, which are easily disturbed due to the interconnected nature of the surface and subsurface. The anthropogenic impacts on karst are deleterious to the ecosystems that are dependent on the karst environment and also to groundwater supplies. The Karst Disturbance Index (KDI) is a holistic tool used to measure anthropogenic impacts associated with karst environments, which has been applied and refined through studies performed in Florida and Italy, yet still remains untested and susceptible to modification for other areas. Application of the KDI in Arecibo, Puerto Rico, which is geographically isolated, and highly vulnerable due to its sensitive karst resources, provides an opportunity to test the index in an island setting. This research resulted in two KDI scores for the study area using both the original and recently modified methods. The scores reflect a significant to severe disturbance to the municipality’s karst environment of 0.54 and 0.68, respectively. Issues regarding the KDI were found from the application and comparison of these methodologies and revealed the need for adding additional indicators, including Mogote Removal and Coastal Karst, as well as several additional refinements and recommendations pertaining to scale, weighting, and incorporating the two methods together to create a single, more practical KDI tool. The disseminated results of the assessment of the area using the KDI will educate and help to foster stewardship of this vital resource in Puerto Rico.