Satellite evidence of episodic greening associated with extreme rainfall events in the Sechura desert

Vegetation and biocrust activity in hyper-arid ecosystems depends on infrequent rainfall pulses that trigger rapid but short-lived biological activity. In the Sechura Desert of northern Peru, extreme El Niño events trigger exceptional rainfall, but the frequency, spatial distribution, and climatic controls of the resulting greening events have not been quantified. Here, we quantified episodic greening across the Sechura Desert from 2001 to 2025 using 250-m MODIS NDVI and examined its relationship with rainfall events. We found that hyper-arid coastal ecosystems remained largely dormant and greened almost exclusively during the extreme rainfall events in 2017 and 2023. In contrast, inland ecosystems experienced more frequent greening pulses over 2001-2025. Highly episodic greening events exhibited a critical activation threshold, remaining dormant until cumulative seasonal rainfall exceeded approximately 0.38–0.58 m, a value only reached during Coastal El Niño years. Areas exhibiting episodic greening covered 3183.51 km 2 (12.3% in the Sechura Desert) and over 12,100 km 2 along the Peruvian coastal desert. These results provide the first long-term, spatially explicit assessment of greening pulses in the Sechura Desert and demonstrate that, during the 25-year MODIS era, these hyper-arid ecosystems remained functionally dormant for most of the period, awakening only during extreme coastal warming events.