<![CDATA[Abstract. Oktavianingsih L, Susanto D, Putra MD, Mukhlis, Rahman R, Yudistyana R, Putra YGS. 2026. Pteridophyte diversity at set-aside conservation areas in the natural gas industrial area in Bontang, East Kalimantan, Indonesia. Biodiversitas 27 (5): d270535. https://doi.org/10.13057/biodiv/d270535. Pteridophytes (ferns) are ecologically important plants that contribute to oxygen production, moisture retention, erosion control, and environmental monitoring. Their conservation is therefore relevant not only in natural habitats but also within production and industrial landscapes. This study assessed fern species diversity, habitat preferences, distribution, and conservation status within a natural gas industrial area in Bontang, East Kalimantan, Indonesia. Field surveys were conducted annually in July from 2022 to 2025 at 11 locations using cruise and purposive sampling. Species were identified based on morphological characteristics and supported by taxonomic references and online databases. A total of 69 species representing 38 genera and 19 families were recorded, with Pteridaceae (16 species), Polypodiaceae (11), and Thelypteridaceae (11) being the most species-rich families. Most species were terrestrial (45 species; 65%), followed by epiphytic (16; 23%), climbing (6; 9%), and terrestrial-epiphytic species (2; 3%). Lygodium circinatum and Pyrrosia piloselloides were frequently recorded across the study area, whereas Helminthostachys zeylanica and Platycerium coronarium had restricted distributions. Most species were categorized as Not Evaluated by the IUCN Red List and Not Listed by CITES, indicating limited formal conservation assessment rather than confirmed population security. P. coronarium warrants particular attention because of its recognized conservation concern in parts of Southeast Asia. Overall, this study provides a baseline inventory of fern diversity in an industrial landscape and supports future ecological monitoring, conservation planning, and population-level studies in East Kalimantan, Indonesia.]]>
