Long-term (1990–2019) monitoring of forest cover changes in the humid tropics

Background

Tropical moist forests are essential for biodiversity, climate regulation, and global carbon storage, yet they face increasing pressure from deforestation and degradation. Accurate, long-term monitoring of forest dynamics is necessary to support climate policies, including REDD+ and Nationally Determined Contributions (NDCs). Previous studies have provided partial insights, but a comprehensive spatial and temporal characterization of forest degradation and recovery remains limited. Advances in satellite imagery and cloud computing now enable consistent monitoring at pantropical scales.

Goals and Methods

This study provides a comprehensive assessment of tropical moist forest changes from 1990 to 2019 using Landsat imagery at 30-meter resolution. It applies a wall-to-wall mapping approach (a comprehensive, seamless coverage of a specific geographic area, creating a complete mosaic of data (such as forest cover, land use, or infrastructure) without gaps) to quantify deforestation, degradation, and forest recovery annually. The methodology introduces a novel classification of sequential forest transitions, including undisturbed forest, degraded forest, deforested land, and regrowth stages. Disturbances are detected using time-series analysis of satellite observations, capturing both short-term degradation events and long-term land-use changes.

Conclusions and Takeaways

This study finds that 17% of tropical moist forests have been deforested since 1990, with an additional 10% currently degraded. Degradation emerges as a critical precursor to deforestation, occurring in nearly half of forest loss cases. The results highlight increasing disturbance trends and warn that undisturbed forests may decline significantly by 2050 if current rates persist. For practitioners, the findings emphasize the need to prioritize early detection and prevention of degradation. The dataset provides a valuable tool for policy planning, carbon accounting, and conservation targeting at global and regional scales.