Philip Jacobson, Padang, Indonesia – At low tide along Padang's coastline, fishing boats sit idle, not because of rough seas, but because the water is clogged with timber.
In late November, flash floods from Cyclone Senyar swept through parts of Sumatra, killing residents and damaging roads and homes. Days later, their aftermath surfaced offshore. Logs carried from upstream forests poured out of river mouths and spread along the coast here in Padang, the capital of Indonesia's West Sumatra province, blocking access to the sea and cutting off the livelihoods of hundreds of fishers.
The mass of floating wood has made it impossible for fishers to pass, with some intact logs measuring up to 90 centimeters (35 inches or nearly 3 feet) in diameter.
"For the past two days, the logs have been piling up. If we try to go out, the boats could be damaged," Syafri Juni, a fisher from Patenggangan Beach in Padang, told Mongabay on Dec. 10.
The formation of a hurricane in the Malacca Strait was an extremely rare occurrence, scientists say, and a devastating one – the storm killed more than 1,000 people across Indonesia, Malaysia, Thailand and Sri Lanka. On the island of Sumatra, torrential rains hit a landscape whose capacity to soak up rainfall has been compromised by decades of rainforest clearance.
Syafri had not gone to sea for the past week because of the debris, a situation he said many other fishers were facing. According to him, around 150 people in the Patenggangan area depend on fishing for their livelihoods. There are about 40 boats, including 14 trawlers that each employ more than a dozen crew members and a number of small vessels shared by 10-15 people.
On a normal day, these fishers earn from 50,000-150,000 rupiah ($3-9), but the timber-choked sea has halted their work. Many have been forced to buy essentials on credit from local stores to cover daily needs.
"Shop owners are starting to complain," he said.
Syafri described seeing large meranti logs, 60-90 cm in diameter, creaking and grinding as waves push them against coastal breakwaters. "It could take a month to clear this," he said. "And there's mud that came along with the logs, settling on the seabed. It makes going to sea extremely difficult."
Another fisher, Rustam, did not hide his anger. The government, he said, had long turned a blind eye to illegal logging, with fishers left to bear the losses from the timber swept out to sea.
"The government should be firm – it's the people and the fishers who suffer," he said. "Who caused this, and who is feeling the impact?"
Marine scientist Harfiandri Damanhuri of Bung Hatta University in Padang warned that flash floods carrying large volumes of timber and mud would have serious consequences for marine ecosystems.
Instead of quickly settling on the seabed, he explained, the mud remains suspended in the water column for some time. "This sediment blocks sunlight, unlike sand, which sinks," he said.
The mud comes from alluvial soil, eroded topsoil and riverbanks stripped by fast-moving floodwaters, according to Harfiandri. By reducing light penetration, it disrupts phytoplankton photosynthesis, potentially killing coral. It can also cause algal blooms and contribute to rising sea surface temperatures.
Harfiandri called for authorities to systematically monitor sediment buildup and other environmental changes brought on by the disaster.
"The Ministry of Marine Affairs and Fisheries should also be involved, as it has jurisdiction over coastal areas, while environmental agencies oversee river basins," he said. "There is already a watershed working group that could be activated."
A new satellite analysis by the Indonesian Forum for the Environment (Walhi), the nation's largest environmental NGO, identified at least 15 alleged illegal logging sites inside protected forest areas and the Bukit Barisan Wildlife Reserve, a designated conservation zone. The analysis showed severe environmental damage in the upper reaches of the Air Dingin River watershed.
These logging sites are located on steep terrain, significantly increasing the risk of soil erosion and runoff into rivers. Walhi said the size of the cleared areas ranges from 1 to 5 hectares (2.5-12.3 acres), reinforcing indications that the recent flash floods across parts of West Sumatra were exacerbated by deforestation upstream.
Diki Rafiqi from the Padang Legal Aid Institute (LBH Padang) said the scale of the disaster reflects the declining carrying and absorption capacity of upstream ecosystems. He said satellite imagery shows deforestation occurring between 2020 and 2024 across protected areas, wildlife reserves and the ancient forests of Kerinci Seblat National Park. The affected areas include Malalak subdistrict and the Padang Laweh Malalo traditional administrative unit, which were among the hardest-hit due to the loss of natural water catchment zones.
"Water catchment areas have already been converted to other uses. As a result, when cyclones bring high-intensity rainfall, there are no longer any areas left to absorb the water because of deforestation," he said.
Diki added that local governments are not equipped to handle disasters of this magnitude, particularly given limited end-of-year budgets.
"We need strong law enforcement," he said. "Deforestation in West Sumatra is happening every minute. At the very least, 1 hectare of forest is lost each day due to deforestation."
The ongoing disaster in Sumatra has underscored how closely connected land and sea ecosystems are, with environmental damage on land now visibly spilling into coastal waters, said Susan Herawati, the secretary-general of national NGO the People's Coalition for Fisheries Justice. When forests are poorly managed, she said, the consequences extend beyond rivers and estuaries into coastal waters and surrounding islands.
"This actually shows that the sea and the land are inseparable," Susan told Mongabay. "When forest governance is bad, it is no surprise that the impacts reach the sea as well."
Susan called for urgent reforms in forest governance and stronger political accountability, warning that without decisive action, environmental damage and human suffering will continue to escalate.
In response to the situation, six Sumatran legal aid groups issued a joint statement urging Jakarta to take stronger action. They called on the president to declare a national disaster status for Aceh, North Sumatra and West Sumatra provinces, and to open access to humanitarian aid, arguing that the scale of destruction exceeds the capacity of local authorities.
President Prabowo Subianto has declined offers of international assistance and insisted that Indonesia can stand on its own two feet.
"Thank you for your concern – [but] we are quite capable; Indonesia is able to overcome this," the president told a cabinet meeting this week.
[Basten Gokkon contributed to this story. He is a senior staff writer for Indonesia at Mongabay. Find him on X @bgokkon.]