National-Scale Mapping of Oil Palm Plantation Ages in Indonesia Using Global Canopy Height Data on Google Earth Engine

Abstract

The oil palm (Elaeis guineensis) is one of the most strategic plantation commodities in Indonesia. However, spatially explicit information on plantation age remains limited, which hampers evidence-based decision making for productivity assessment, replanting prioritization, and sustainable plantation management. This study is to investigate the spatial distribution of oil palm age across Indonesia based on 10 m Global Canopy Height (GCH) product within the Google Earth Engine (GEE) platform. The methodology included canopy-height extraction and masking, age estimation using a height–age regression model, multi-site validation, and national-scale mapping. Canopy height obtained from GCH was compared with field measurements at the Asahan calibration site were strongly correlated (R² = 0.85). The age model was validated using planting-year records from five plantations in Sumatra and Kalimantan. At the Asahan calibration site, the model reproduced recorded ages with the suitable is R² = 0.88 and RMSE = 2.8 years. However, model reliability may vary depending on topography, weather conditions, plantation management, and oil palm variety. The model was applied to 11.62 million hectares of mapped oil palm area. The mapped plantations were dominated by mature stands (5–25 years, 43.7%), followed by young stands (0–5 years, 30.3%) and old stands (>25 years, 26.1%). Regional mapping shows that Sumatra contains a high density of old stands targeted for replanting, particularly in Jambi, where old stands account for 30.4% of the mapped area. In contrast, Central Kalimantan is dominated by young stands, which account for 40.0%. At the national level, the resulting age map provides a spatially consistent baseline for identifying replanting priorities, supporting productivity monitoring, improving plantation inventory, and informing sustainable oil palm governance across Indonesia.