National analysis on variations in estimates of forest cover dynamics over India (2001–2020) using multiple techniques and data sources

This study evaluated multiple methodologies for monitoring forest and tree cover dynamics in India using remote sensing. The Forest Survey of India (FSI) biennially maps forest and tree cover, reporting areas under three crown density classes along with a pixel-level change matrix. Global Forest Watch (GFW) data use an annual Landsat time series to detect tree loss pixels from 2001 to 2020 and global data on new plantations. Cumulative forest to non-forest class transitions of 12.1 Mha was estimated by counting pixel-level using a change matrix reported by FSI and 2.43 Mha was estimated through tree loss using GFW data. However, FSI and global plantations data indicated new areas brought under tree cover/forest 14.5 Mha and 11.1 Mha, respectively. Part of these variations was due to differences in definition and methodology. This study highlights the need for mapping the regular loss and new areas under tree cover, which simple statistics of net forest cover change are unable to capture. Additionally, the locations of loss and plantations were visualized as spatial layers of a 1 × 1 km grid. Geo-located loss and gain areas would be of great interest in spatially capturing dynamics of forest biomass and carbon cycle. Enhanced greening of India reported in many studies is also supported. The nature of interventions leading to additional tree cover has also been highlighted.