The Sumatera Floods Are an Ecological Disaster, Marking Maladaptation to the Climate Crisis

The large scale of flooding and landslides in northern Sumatera over the past week is not merely a hydrometeorological disaster triggered by high rainfall intensity, but also marks an ecological crisis and spatial governance issues in Sumatra. This disaster serves as a moment to audit the extractive industries and deforestation in this area, which have led to maladaptation to the climate crisis.

The Head of the National Disaster Management Agency (BNPB), Suharyanto, stated that as of Sunday (30/11/2025), at least 442 people have died and 402 are missing due to the disaster that struck Aceh, North Sumatera, and West Sumatera. The highest number of casualties is in North Sumatera, with 217 people dead and 209 missing.

In West Sumatera or Sumbar, according to data from BNPB, the death toll has reached 129 individuals, with 118 people reported missing. Meanwhile, in Aceh, the death toll is recorded at 96 fatalities, with 75 individuals still unaccounted for.

Data from the Meteorology, Climatology, and Geophysics Agency (BMKG) indicates that Cyclone Senyar has triggered heavy to extreme rainfall in Aceh, North Sumatra, and West Sumatra. The highest rainfall intensity was recorded in Aceh, specifically in the Kuala district of Bireun, with an intensity of 411 millimeters (mm) per day on November 25-26, 2025, as stated by the Head of the Aceh Climatology Station, Muhajir.

Cyclone Senyar was reported to have made landfall in the Aceh Province on that day, before subsequently turning back into the Malacca Strait and entering Malaysian territory.

On that day, five regions in Aceh experienced extreme rainfall exceeding 370 mm. In addition to Kuala District, rainfall of up to 397.4 mm was recorded in Karang Baru District, Aceh Tamiang, 382 mm in Langsa Baro District, Langsa City, 376.6 mm in Pasie Raja District, South Aceh Regency, and 376.6 mm in Meureudu District, Pidie Jaya Regency.

Extreme rainfall exceeding 150 mm has also been recorded in various regions of Aceh, including the northeastern coastal areas of Aceh, Sabang City, Aceh Besar, Aceh Singkil, Aceh Selatan, Aceh Tenggara, and Subulussalam City.

In North Sumatera, a rainfall record of 386 mm per day was recorded at the Cempa Rain Gauge in Langkat Regency on November 26-27, as reported by the Head of the North Sumatra Climatology Station, Wahyudin. On that day, extreme rainfall exceeding 300 mm was also recorded in the cities of Medan, Binjai, Deli Serdang, Batubara, and Humbang Hasundutan.

The intensity of rainfall exceeding 380 mm per day, and in the case of Aceh surpassing 400 mm per day, is the highest recorded in this region, and also among the highest in Indonesia.

As a comparison, the rainfall record in Jakarta, which has been recorded over 150 years since the colonial era, occurred on New Year's Day 2020, amounting to 377 mm per day at Halim Perdanakusuma Airport. This rainfall record triggered significant flooding in Jakarta.

Meanwhile, the tropical cyclone Cempaka, which was near the island of Java in 2017, caused record heavy rainfall in several areas, such as in Pacitan with 383 mm in a day on November 27. The Seroja cyclone in 2021 triggered a record rainfall of up to 332.1 mm in a day in Kupang, East Nusa Tenggara (NTT), in April 2021.

The record intensity of rainfall in Indonesia almost always occurs with the phenomenon of tropical cyclones. According to the Director of Meteorology at BMKG, Andri Ramdhani, this cyclone is an anomaly because it formed at a low latitude, 4.5 degrees North Latitude in the Malacca Strait, an area that climatologically should not support the formation of tropical cyclones.

A series of atmospheric anomalies, such as a strengthening of the Asian monsoon, a major convergence in the Strait of Malacca, warm sea temperatures, abrupt changes in the speed or direction (shear) of low-lying winds, increased convection from regional-scale phenomena such as the MJO, Kelvin, and Rossby Waves, and the narrow geography of the strait, create conditions for cyclones to develop in areas previously considered safe.

BMKG climate researcher Siswanto added that as the oceans warm due to climate change, Indonesia is no longer fully protected from the threat of tropical cyclones, whether from the west, north, or south.

The phenomenon of tropical cyclones making landfall in Indonesia, which used to occur over decades to centuries, can now happen within a matter of years. Prior to Cyclone Senyar, Tropical Cyclone Vamei had previously appeared in this region in 2001, and Cyclone Seroja passed through NTT in 2021.

With the threat of these increasing sources of danger, Indonesia should adapt by increasing its capacity to reduce the risk of hydrometeorological disasters.

Capacity building can be achieved by enhancing environmental support and the community's capacity to anticipate flood and landslide disasters, including improving the early warning system.

In fact, the carrying capacity of our environment is declining, while the threats are increasing. The Country Director of Greenpeace for Indonesia, Leonard Simanjuntak, stated that the severity and extent of the damage in the disaster should serve as an alarm that massive destruction is occurring in the ecological protective functions in Sumatra, particularly in river basins, hilly areas, and other vulnerable regions.

"The environmental carrying capacity of Sumatra is already critical, as its forests are being impacted and torn apart by thousands of extractive industry permits," said Leonard. On the other hand, climate anomalies due to extreme warming in the waters of the Malacca Strait, manifested in the form of Tropical Cyclone Senyar, prove that the climate crisis is indeed occurring.

"The Sumatra disaster should serve as a reminder for all of us to take immediate action to stop global warming, which will lead to a series of extreme weather events and new disasters in the future," he stated.

Data from the Ministry of Energy and Mineral Resources (ESDM) processed by the Mining Advocacy Network (JATAM) shows that Sumatera is extensively opened for mineral and coal mining. There are at least 1,907 active mineral and coal mining business license areas covering a total area of 2,458,469.09 hectares.

The Sumatra disaster should serve as a reminder for all of us to take immediate action to halt global warming, which will lead to a series of extreme weather events and new disasters in the future.

The density of these permits is concentrated in Bangka Belitung (443 permits), Riau Islands (338), South Sumatra (217), West Sumatera (200), Jambi (195), and North Sumatera (170). Meanwhile, other provinces such as Lampung, Bengkulu, Aceh, and Riau are also filled with dozens to hundreds of permits both on land and at sea.

According to JATAM, the pressure on the Sumatera ecosystem does not stop at mineral and coal mining, but also includes deforestation for various other reasons, including power plants. At least 28 Hydroelectric Power Plant (PLTA) projects are operating or being developed on this island, with the largest concentration in North Sumatra at 16 locations, followed by Bengkulu (5 PLTA), West Sumatra (3), Lampung (2), and Riau (2).

The Executive Director of Satya Bumi, Andi Muttaqien, believes that the impact of the flash floods in Sumatera could be significantly minimized if companies and the government thoroughly and transparently review every permit, project, and forest opening.

"The high number of casualties should serve as a reminder for the government to truly restore the damaged landscapes, re-evaluate, and review the permits of environmentally destructive companies," said Andi.

North Sumatera Province has become the most severely affected area. Its regions include Central Tapanuli, South Tapanuli, North Tapanuli, and Sibolga. In Tapanuli, there is the Batang Toru ecosystem, commonly referred to as Harangan Tapanuli, which boasts high biodiversity richness.

Currently, the ecosystem is surrounded by various extractive megaprojects such as the Martabe gold mine owned by PT Agincourt Resources, the Batang Toru hydropower plant, the Pahae Julu micro-hydropower plant, PT SOL which operates geothermal energy, the paper company PT Toba Pulp Lestari, as well as the palm oil plantations of PT Sago Nauli and PTPN III Batang Toru.

Data from Satya Bumi indicates that the concession of PT Agincourt Resources covers an area of 130,252 hectares. Of this, 40,890.60 hectares overlap with the Batangtoru ecosystem, which is home to the Tapanuli Orangutan. Additionally, a concession area of 30,630 hectares also overlaps with protected forests in North Tapanuli, Central Tapanuli, and South Tapanuli.

Meanwhile, of the total area of hundreds of thousands of hectares, Agincourt has opened 603.21 hectares of them until October 2025. The company plans to open another 195 hectares to build a waste storage facility or tailing management facility (TMF).

"The most concerning issue is that the TMF is being built upstream of the Nabirong River Basin and has the potential to spread to the Batangtoru River Basin. In addition, Martabe is being constructed in an area with high seismic activity," Andi added.

The Tapanuli orangutan (Pongo tapanuliensis), the world's rarest great ape species, is now home to fewer than 800 individuals. The International Union for Conservation of Nature (IUCN) listed the Tapanuli orangutan as critically endangered in 2017.

With the current pace of climate change, adaptation should be the key to ensuring survival. Nevertheless, there are many examples of incorrect adaptation practices, referred to in the 2022 report of the Intergovernmental Panel on Climate Change (IPCC) as maladaptation.

Maladaptation is defined by the IPCC as actions that can lead to an increased risk related to climate, including through increased greenhouse gas emissions, heightened vulnerability to climate change, or a decline in well-being, either currently or in the future.

The climate scientists who compiled this report also provided several examples of maladaptation, such as the construction of dams, both for irrigation and power generation. At certain levels, these policies seem to be beneficial.

However, if this disrupts local communities' access to land and forest resources, such interventions result in some individuals becoming more vulnerable to climate impacts, in addition to their effects on biodiversity.