• Cyclone Senyar was an unusually rare event for Sumatra, but the scale of destruction cannot be explained by weather alone. Decades of deforestation, mining, plantations, and peat drainage left watersheds unable to absorb intense rainfall, turning extreme weather into a mass-casualty disaster.
• Forest loss and land conversion have systematically weakened Sumatra’s natural defenses. The island has lost millions of hectares of forest since 2001, increasing runoff, destabilizing slopes, and amplifying floods and landslides when heavy rain hits.
• Peatland drainage has created a hidden, compounding flood risk. Canals dug for plantations dry and compact peat soils, causing land subsidence and transforming once water-retentive landscapes into low-lying areas prone to chronic inland and coastal flooding.
• Rising exposure, not just rising hazards, is driving future risk. Urban expansion into floodplains and degraded catchments means that even rare storms now endanger more people and infrastructure, locking much of Sumatra into a cycle of disaster unless land-use governance changes.