22 years of MODIS data flag resilience-loss signals in 27% of global ecoregions

A study of 22 years of satellite vegetation records has found statistical early-warning signals in 27% of the world's terrestrial ecoregions, covering 35.3% of the land area analysed. The researchers used 266 monthly kernel NDVI observations from MODIS/Aqua (July 2002 to August 2024, 0.05° resolution). They combined K-means clustering of month-by-month vegetation trends with change in lag-1 temporal autocorrelation, a marker of slower recovery, between the first and last 133 months.

Flagged ecoregions lie across tropical South America, Africa and Asia, as well as Central and South Asia, north-western North America, central Europe and high latitudes. Browning is expected mostly in South America, tropical Africa and north-western North America, and greening in Asia and Europe. Examples include the Angolan wet miombo woodlands, where a cluster covering 21% of the area showed declining vegetation in every month. The authors stress these are warning signals, not evidence of collapse, and the study cannot attribute causes.

Why it matters: The ecoregion-level maps show where satellite time series suggest slower vegetation recovery, including in Angolan miombo and tropical African ecosystems. They indicate where regional monitoring and field studies could be targeted, though the method cannot identify causes.