Indonesian environmental activists say the floods and landslides that have devastated parts of Sumatra have been made worse by extensive deforestation driven by the approval of hundreds of extractive permits.
Unusually destructive storms and monsoonal flooding since last week have killed more than 1,300 people across Indonesia, Sri Lanka and Thailand.
Indonesia was hit the hardest, with the death toll exceeding 700 and at least a further 500 reported missing.
More than 1.2 million people have been displaced in Sumatra as a result, according to Indonesia's disaster management agency.
Meteorologists have explained the devastation by pointing to the unusual interaction between Typhoon Koto and Cyclone Senyar in the Malacca Strait — rare because cyclones do not typically form on the equator.
Indonesian environmental experts and activists, however, said deforestation and mining activities in Sumatra had intensified the effects of the disaster and led to more deaths.
'Someone must be held responsible'
Dodik Ridho Nurochmat, a professor in forest policy at IPB University in Bogor near Jakarta, said in a statement the landslides were the result of a combination of natural and human factors.
"There are extreme weather conditions, mountainous geography and environmental degradation caused by human activities," he said.
The source of logs that had damaged homes and other structures as they were swept along by floodwaters remained unclear, he said.
"They could come from old logging activities or incomplete land clearing … they may also come from recent logging. Therefore, an investigation is needed," Professor Nurochmat said.
Data from Indonesian Forum for the Environment showed that over 20 years, hundreds of thousands of hectares in North Sumatra, West Sumatra and Aceh have been deforested due to extractive licenses granted to 631 companies.
The group's director, Uli Arta Siagian, said much of the wood harvested was used to produce pulp and paper for export to European countries, while palm oil produced in those regions was exported to India, Malaysia and China.
Indonesia's ecological fragility was increasing, which explained why it was hit so hard by the storms, she said.
"With the buffer or green zone not existing and the ecological infrastructure such as mangroves in coastal areas destroyed, the cyclone could enter the land and ruin people's homes," she said.
Ms Siagian noted that Indonesia had "the third-largest forest in the world" and that Sumatra, its largest island, was home to the Bukit Barisan ecosystem — 90 per cent of which is forest.
"The energy and forest and land use sectors in Indonesia are the biggest contributors for Indonesia's greenhouse [gas emissions]," she said.
The Indonesian government itself has also pointed to the role of land clearing in causing flash flooding and landslides in Sumatra.
"We must prevent deforestation and forest destruction," said President Prabowo Subianto, describing the protection of Indonesian forests as "crucial".
Indonesia's Ministry of Environment said it was investigating the source of thousands of logs that were swept away by flash floods and landslides in several areas of Sumatra.
"The logs swept away by the floods could originate from various sources: decayed trees, river materials, legal logging areas, or misuse of land-rights permits and illegal logging," said Dwi Janunato Nugroho, a ministry spokesperson.
Environment Minister Hanif Faisol Nurofiq told a press conference there were eight companies suspected of allegedly contributing to the worsening of the natural disaster.
These included plantation firms, gold mining operators and palm oil producers, he said, with main activities taking place in the Batang Toru river basin in North Sumatra.
"Someone must be held responsible for this disaster," he said.
Existing environmental approvals for the eight companies would be revised if authorities found any misconduct, Mr Nurofiq said.
Ramlan, a resident of Langkar in North Sumatra who remains unable to return to his home, blames the existence of a nearby palm oil plantation.
"The Leuser National Park has been taken by palm oil," he said, referring to a park that is one of the two remaining habitats for Sumatran orangutans and also home to elephants, rhinoceroses and tigers.
"I think that is the culprit of this flash flood, the heavy rainwater could not be contained anymore by the forest," Ramlan said.
"Now, it is small people like us that bear the burden and the business owners from outside Langkat who enjoy the profit."
Not only caused by illegal activities
As he expressed condolences to the affected communities in Sumatra, Mr Prabowo, the president, suggested environmental conservation should be included in school curricula.
"We may need to add lessons on awareness and the importance of protecting our natural environment, preserving our forests, truly preventing tree felling and forest destruction," he said.
"We must also keep our rivers clean."
But his remarks were criticised by Indonesia's Mining Advocacy Network, which described them as "political hypocrisy".
"On the other hand, his administration is reinforcing an extractive economic model through accelerated mining downstream projects, expansion of large energy projects, and consolidation of resource oligarchies in upstream river basins that are home to communities in Aceh, North Sumatra and West Sumatra," the network's Melky Nahar said.
Last December, for example, Mr Prabowo was explicitly calling for the expansion of palm oil plantations.
"Palm oil's a tree, right?" he said at the time.
"Don't be scared of what people say about it being dangerous or causing deforestation."
Data from the Energy and Mineral Resources Ministry showed in Sumatra there were at least 1,907 active mining permits covering a total area of almost 2.5 million hectares.
But Mr Nahar said the problems were not only coming from illegal mining, but also licensed projects.
"This narrative that keeps blaming illegal mining obscures the fact that thousands of legal permits for mining, hydropower plants, geothermal projects, palm oil and forestry concessions dominate the upstream watershed areas in Aceh, North Sumatra and West Sumatra," he said.
"We know this after overlaying all mining concessions and energy projects across Sumatra."
Mr Nahar said the Prabowo administration should lead a comprehensive audit, especially into large-scale land-based investments in Sumatra and other islands.
"In Sumatra, one of the most dangerous potential threats is earthquakes," he said.
"This is because several projects, including geothermal plants that can trigger earthquakes, are located directly on fault lines, such as the Batang Toru hydropower plant, thus escalating the risk."
The Indonesian archipelago lies on the "Ring of Fire", an arc of volcanoes and fault lines along the Pacific Basin known as the most active earthquake zone on the planet, making it highly prone to earthquakes and volcanic eruptions.
