The Molluscs of the Rocky Outcrops in Sant Llorenç del Munt i l’Obac Natural Park: A Study of the Impact of Trampling and Erosion.- This study investigates the diversity of land snails in the rocky outcrops of the Montcau area and evaluates the effects of visitor trampling and erosion. A total of 42 mollusc species were recorded, but heavily trampled areas supported significantly fewer individuals, particularly Xerocrassa montserratensis. The authors conclude that regulating visitor access and controlling erosion are essential to protect these sensitive habitats.