Remote sensing insights into rubber-forest interface dynamics in the Western Ghats of Kerala, India towards socio-ecological sustainability

Expansion of agriculture along forest edges influences the socio-ecological sustainability of agricultural and forest ecosystems as well as human livelihoods. This study assessed the spatio-temporal extent of rubber plantations located inside and adjacent to forests in Kerala, India, using multi-decadal geospatial datasets and developed a rubber-forest interface area index (RFAI) to quantify district-level contributions to statewide rubber-forest adjacency. Spatial extent of rubber plantations and forest boundaries for the period 1970, 2000 and 2022 was generated using Survey of India toposheets, Landsat 7 ETM+, Sentinel-2 MSI satellite data and ground-truth information. Results indicate an accelerated expansion of RFAI, with cumulative increases of 22,241 ha between 1970 and 2000 and 31,509 ha between 2000 and 2022. Of the total rubber area in Kerala in 2022, approximately 1.9% occurs inside forests, while 8.1% and 5.4% are situated within the 0–500 m and 500–1000 m forest-edge zones, respectively. District-level RFAI values for 2022 show the highest contributions in Idukki, Malappuram, Kottayam, Pathanamthitta, Kollam, Ernakulam, Palakkad, Thrissur and Kasaragod. The long-term expansion observed in forest-proximal zones highlights a spatial shift of rubber cultivation towards forest margins, where ecological processes and human–wildlife interactions converge. These results highlight the socio-ecological relevance of mapping rubber-forest interfaces for sustainable management of rubber plantations, forest ecosystem conservation and the well-being of forest-dependent communities in man–animal conflict zones. Overall, the study demonstrates the value of spatial interface metrics such as RFAI for strengthening socio-ecological assessments and supporting informed land-use planning in tropical countries undergoing rapid agricultural expansion.