Show caves are natural cavities equipped with infrastructure that facilitates access and typically requires an entrance fee. Nowadays, cave tourism generates approximately 3 billion/year of U.S. $ (value 2028), representing an important cultural and economic resource. However, the presence of visitors introduces multiple disturbances, with consequent impacts on cave ecosystems. Among these, artificial lighting plays a central role by promoting the growth of photosynthetic biofilms known as lampenflora, mainly composed of cyanobacteria, diatoms, and green algae. Lampenflora proliferation leads to physical, chemical, and aesthetic alterations of cave surfaces. Moreover, the introduction of external microorganisms by visitors can modify the composition and functionality of the native subterranean microbiome. For these reasons, lampenflora represents a direct proxy of anthropogenic disturbance, being strictly dependent on artificial lighting and human activity. In this context, lampenflora can be more appropriately defined as a functional indicator of tourism-driven ecosystem alteration in show caves.

We measured lampenflora concentration in fourteen Italian show caves, alongside environmental variables such as light intensity, moisture and tourism intensity. Monitoring of lampenflora allowed us to assess the current level of disturbance across different cave systems. These results provide a first comparative baseline for evaluating anthropogenic pressure in Italian show caves, highlighting the key role of artificial lighting and tourism intensity in shaping biofilm development. This approach represents a practical tool for long-term monitoring and offers valuable support for the development of sustainable management strategies aimed at balancing conservation needs with touristic use.