The devastating flash floods that recently struck three provinces across Sumatra—Aceh, North Sumatra, and West Sumatra—have starkly exposed the alarming extent of forest cover degradation in these critical regions.
At the heart of this environmental crisis lies the Tropical Rainforest Heritage of Sumatra (TRHS), a site of immense global ecological importance. Designated as a UNESCO World Heritage site in 2004 for its unparalleled biodiversity value, the TRHS has regrettably been on UNESCO’s World Heritage in Danger list since 2011, a testament to the escalating threats imperiling its survival.
Spanning an expansive area of approximately 2.5 million hectares, the TRHS encompasses three vital national parks: Gunung Leuser National Park, Kerinci Seblat National Park, and Bukit Barisan Selatan National Park. This vast and biodiverse landscape is a sanctuary for an incredible array of life, hosting around 10,000 plant species, including 17 endemic genera. It is also home to over 200 species of mammals and approximately 580 bird species, with 465 resident species and 21 unique endemic birds.
Among its most iconic inhabitants are critically endangered key mammal species such as the Sumatran orangutan, Sumatran tiger, Sumatran rhinoceros, Sumatran elephant, and the Malayan sun bear. These creatures represent a fragile ecosystem, facing immense pressure from human activities.
UNESCO itself has articulated the grave dangers, stating, as quoted on Monday (December 1st), that “The World Heritage Committee inscribed TRHS on the Danger List due to threats such as poaching, illegal logging, encroachment for agricultural activities, and plans for road construction crossing the area. Road access opens up opportunities for practices that disrupt the sustainability of these national parks.” This statement underscores how human expansion and illicit activities directly undermine the ecological integrity of these protected areas.
The recent catastrophic floods across Sumatra have brought renewed attention to the urgent issue of diminishing forest cover. The Ministry of Forestry (Kemenhut) previously identified extreme rainfall and the extensive loss of forest cover as the primary triggers for the severe floods that afflicted several areas in Sumatra on November 25–27, 2025. These affected regions included North Aceh Regency, Langkat Regency, Central Tapanuli Regency, Sibolga City, and South Tapanuli Regency.
During this period, rainfall reached unprecedented levels, exceeding 150 mm per day. The sheer volume of water caused river discharges to increase dramatically in a short span, overwhelming their natural capacity and leading to destructive overflows into residential areas.
Data from Global Forest Watch paints a grim picture of this ecological decline between 2002 and 2024. North Sumatra alone lost a staggering 390,000 hectares of humid primary forest, accounting for 25% of its total tree cover loss during this timeframe. This severe reduction translates to a 19% decrease in the province’s total humid primary forest area.
Similarly, West Sumatra experienced a loss of 320,000 hectares of humid primary forest, contributing to 44% of its overall tree cover loss in the same period, with its total humid primary forest area shrinking by 14%. Aceh also suffered significant deforestation, losing 320,000 hectares of humid primary forest, which represents 38% of its total tree cover loss and a 9% reduction in its total humid primary forest area.
The human toll of these disasters has been tragic. The National Disaster Management Agency (BNPB) reported that as of Sunday (November 30th) at 6:00 PM WIB, a total of 442 people had perished across Aceh, West Sumatra, and North Sumatra. Among the fatalities, 217 were in North Sumatra, 129 in West Sumatra, and 96 in Aceh. Additionally, 402 individuals were still reported missing—209 in North Sumatra, 118 in West Sumatra, and 75 in Aceh—while 646 people sustained injuries, highlighting the profound and devastating impact of these environmentally exacerbated natural catastrophes.
Summary
The recent devastating flash floods across Aceh, North Sumatra, and West Sumatra have highlighted severe forest cover degradation, with extreme rainfall and extensive deforestation identified as primary triggers. This crisis impacts the Tropical Rainforest Heritage of Sumatra (TRHS), a UNESCO World Heritage site designated in 2004 but on the “World Heritage in Danger” list since 2011 due to threats like illegal logging, agricultural encroachment, and road construction. The TRHS, spanning 2.5 million hectares and home to diverse flora and critically endangered fauna, faces immense pressure from human activities.
Between 2002 and 2024, Global Forest Watch data reveals significant primary forest loss across these provinces: North Sumatra lost 390,000 hectares, West Sumatra 320,000 hectares, and Aceh also 320,000 hectares. These losses represent a substantial reduction in humid primary forest area for each province. The human impact has been tragic, with 442 fatalities, 402 missing, and 646 injured reported by the National Disaster Management Agency (BNPB) as of November 30th.
