Monitoring Forest Landscape Restoration Success Using Sentinel-2 NDVI and Field Measurements in Timor-Leste

Abstract

Abstract Forest Landscape Restoration (FLR) has become an important strategy for reversing land degradation and improving ecosystem resilience in tropical drylands. However, quantitative evaluations of restoration effectiveness remain scarce in Timor-Leste, particularly those integrating satellite-based monitoring with field observations. This study assessed vegetation recovery following reforestation activities within a 148-ha restoration site in Balak, Manatuto, Timor-Leste, using multi-temporal Sentinel-2 imagery and field-based ecological measurements. Vegetation dynamics were evaluated using the Normalized Difference Vegetation Index (NDVI) derived from Sentinel-2 images acquired in May 2022 and May 2026. NDVI differencing was applied to quantify vegetation change, while field data collected from 29 monitoring plots were used to assess seedling survival and growth performance. Pearson correlation and linear regression analyses were employed to examine relationships between vegetation growth indicators and restoration performance. The results indicated substantial vegetation improvement across the restoration area. Mean NDVI increased from 0.288 in 2022 to 0.475 in 2026, representing a 65% increase in vegetation greenness. Approximately 77.6% of the sites experienced moderate to significant vegetation recovery based on ΔNDVI analysis, whereas only 2.3% showed vegetation decline. Field assessments revealed that 62.1% of monitoring plots were classified as high-recovery sites and only 6.9% as low-recovery sites. A significant positive relationship was observed between average plant height and growth percentage ( r = 0.423, R ² = 0.179, p = 0.022), indicating that vegetation structural development was associated with restoration performance. These findings demonstrate that the AFoCO-supported reforestation programme has effectively accelerated vegetation establishment and improved ecosystem condition within a degraded tropical dryland landscape. The integration of Sentinel-2-derived NDVI indicators with field measurements provides a practical, cost-effective, and scalable framework for monitoring FLR outcomes in data-limited regions and offers valuable evidence to support restoration planning and evaluation in Timor-Leste and comparable tropical dryland environments.

Plant phenotyping relevance

Sentinel-2 NDVIと圃場測定を統合し、植生回復・成長という植物状態を定量評価する監視フレームワークを中心的に適用しているため。

Code and data availability

The paper's phenotype/trait data (29 plot field measurements: seedling survival, plant height) and Sentinel-2 NDVI datasets are not publicly deposited; the Data Availability Statement says they are available from the corresponding author upon reasonable request. No author analysis code or repository is mentioned.

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