Banjar, Indonesia – Indonesia's government continues to review mines and plantations in the river basins of southern Borneo, months after more than 7% of the population there was impacted by flooding in December last year.
"An audit is still in progress," environment ministry spokesperson Yulia Suryanti told Mongabay Indonesia.
South Kalimantan is one of five Indonesian provinces on the highly biodiverse island of Borneo, which Indonesia shares with Brunei and Malaysia. The southeastern province is particularly vulnerable to flooding during the region's main rainy season – at least 35 people were killed during major floods that destroyed more than 100,000 homes in 2021.
The population of South Kalimantan was almost 4.4 million as of the 2020 census, the most recent conducted by the government. Meanwhile, data from Indonesia's disaster management agency showed that nearly 290,000 people were affected by the latest annual floods since the beginning of December last year.
Eleven out of the 13 cities and districts that make up the province experienced flooding by January.
Civil society organizations say that likely reflects wholesale destruction of old-growth forest throughout the basins of the Barito and Maluka rivers, which run through the province and out into the Java Sea. The Barito is the second-longest river in Borneo, after the Kapuas.
"Across South Kalimantan, especially in the mid and lower sections of the Barito River Basin, a lot of the forest cover has been lost," said Anggi Prayoga, a forestry campaigner at Greenpeace Indonesia.
The head of the forestry department in South Kalimantan, Fatimattuzahra, said it was difficult to pin the blame for flooding on a single factor.
Last September, meteorologists at Indonesia's national weather agency said they expected an early onset of the main rainy season, with a peak in December across much of South Kalimantan. The meteorology agency, the BMKG, tracks seasons to help farmers determine the best time to plant.
The country's disaster management agency, the BNPB, recorded no fatalities during the floods that ensued, but the annual recurrence and extent of flooding has prompted the government to initiate a review of companies operating in catchment areas.
On Dec. 30, Indonesia's environment minister, Hanif Faisol Nurofiq, visited a badly flooded village in Banjar district, where young children followed the government entourage through ankle-deep water.
"The Ministry of Environment has collected data on several companies suspected of violating regulations by clearing large areas of land, and the law enforcement team is still investigating," Hanif, a career forestry civil servant who holds a doctorate in environmental studies, said on Dec. 30.
"Climate change is real," the minister added, "and we must protect our environment."
Watershed moment?
Data from Global Forest Watch showed South Kalimantan province lost 13% of its old-growth forest from 2002-2024, on top of the extensive deforestation that occurred during the second half of the 20th century.
Greenpeace has called on the government to review all forest and land-use permits across the province, and to rehabilitate critical landscapes. The nonprofit's analysis shows less than 1% of the 88,000 hectares (about 217,500 acres) of the Maluka watershed remains as natural forest.
"This condition has caused the area to lose almost all of its function as a catchment area and flood buffer, thereby increasing the vulnerability of the surrounding area to flooding," said Greenpeace's Anggi Prayoga.
The Barito River Basin is a much larger area, spanning 6.2 million hectares (15.3 million acres, or more than twice the size of Belgium) over four of Indonesia's five Bornean provinces. Greenpeace research showed more than half of the Barito watershed in South Kalimantan province was under various commercial permits, including oil palm plantations and mines.
Anggi said that while the analysis on deforestation covered these two watersheds, other catchment areas were also presumed to have suffered various degrees of damage, with commensurate consequences for flooding.
"Forest destruction has direct implications for watershed conditions," said Respati Bayu Kusuma, a researcher at Forest Watch Indonesia, a nonprofit.
"When vegetation in the upstream and along the watershed is reduced, the soil's capacity to retain water is weaker, so the surface runoff actually increases," Respati said, adding that floods were "a matter of time."
A construction boom has further damaged natural drainage channels. When heavy rainfall occurs during high tides, the water has no outlet from residential areas, said Badaruddin, a landscape scientist at Lambung Mangkurat University in Banjarmasin, the South Kalimantan capital.
"Without serious efforts to restore environmental carrying capacity, from protecting upstream forests, restoring bogs and riverbanks, to spatial planning that supports natural function, flooding will continue to recur, even if the rainfall is not extreme," Badaruddin said.
In the aftermath of the fatal 2021 floods, Indonesia's disaster management agency, the BNPB, called for a comprehensive study of flood causes in South Kalimantan. Five years later, the provincial government says a detailed study is needed to understand the causes.
"A comprehensive and thorough study is needed, involving various scientific fields and stakeholders," said Fatimattuzahra, the head of the provincial government's forestry office.
She also pointed to interdepartmental efforts to restore land, and disputed the civil society assessment of the scale of industrial permits authorized in watersheds.
Muhammad Pazri, a lawyer in South Kalimantan, said he hoped the government would carry out a thorough investigation of companies in the area, and take legal action where warranted.
"This can be done through administrative sanctions, civil lawsuits, or criminal prosecution," Pazri said.