Quantitative indexes based on geomorphologic features: A tool for evaluating human impact on natural and cultural heritage in caves

This work deals with the design of a method for evaluating both the degree of conservation of the geomorphologic heritage and the human impact linked to opening karstic caves for tourist use. The methodology was developed in Tito Bustillo Cave, a cave of tourist interest in Northern Spain, declared as a part of a World Human Heritage Site in 2008. A detailed geomorphologic map of the cave floor including natural features and anthropogenic features was drawn up at a scale of 1:250. The map was transferred to a Geographical Information System (GIS), allowing to drawn up a geomorphologic heritage map of the cave by grouping the geomorphologic features in three categories: natural heritage, cultural heritage and geomorphologic impact features derived from tourist use. Four quantitative indexes using several surface parameters derived from the cave heritage map and the surface of the natural cave (SC) were established and measured. The Geomorphologic Heritage Conservation Index (GHC) considers the surface of natural geomorphologic heritage; the Total Anthropogenic Influence index (TA) is calculated from the total surface of anthropogenic features; the Cultural Heritage Index (CH) considers the extent of the Cultural Heritage with a surface expression in the floor cave, while the Index of Geomorphologic Impact linked to Tourist Use (GTU) is obtained from the surface of anthropogenic features derived from cave conditioning for tourist use. The obtained values range from 0.51 to 0.57, suggesting a significant impact on the natural geomorphologic heritage of the cave because of the opening of the cave to tourists. Geomorphologic heritage maps and the derived indexes can serve as useful quantitative tools to enhance cave cultural and natural heritage, and therefore, can contribute to cave management in tourist caves.