Periyar Tiger Reserve (PTR), the largest protected area in the state of Kerala, in India with an area of 925 sq.km. is under severe anthropogenic pressure due to the annual pilgrimage to the Sastha temple (Ayyappa temple), located at Sabarimala, in the south-western Pamba range of the reserve.

The present study explores the extent of forest degradation caused by the pilgrimage activity using the tools of geoinformatics. The land use/ land cover change analysis over the years, observed drastic conversion of dense forest area into other land use like permanent and temporary constructions, open forest, grassland and barren area. The study revealed that Sabarimala pilgrimage and related activities have caused significant loss and changes in the floristic pattern and cover density of the area, but it is confined to areas with direct human interactions only. The NDVI analysis showed the loss in vegetation vigour of the study area.

The fragmentation (31.12%), patchiness (34.37%) and porosity (61%) measures showed high values indicating loss of forest cover, density and diversity in the trekking path, temple and Pamba Triveni areas. The Disturbance Index map showed heavy disturbance along the trekking path from Pamba Triveni to Sabarimala and the temple premises and it is evidently due to the pilgrimage activity. If this trend prevails the damage to the remaining forests would be irreparable. Controlled pilgrimage along with proper conservation programmes is recommended.