As thousands of hectares of flammable peatlands go up in smoke in Sumatra and Kalimantan, Indonesia is facing another crisis caused by decades of unbridled forest clearance to develop oil palm and pulpwood plantations - subsidence.
Millions of hectares of Indonesia's former forest lands are slowly subsiding and could become flooded wastelands unable to grow food or timber-based products in one of the world's most populous nations. Combined with rising sea levels, the scale of the problem becomes even more stark because much of the east coast of Sumatra is just a few metres above sea level.
Mr Marcel Silvius of global non-governmental organisation Wetlands International said between 70 per cent and 80 per cent of Sumatra's peatlands have been drained, largely for agriculture.
"These peatlands will become unproductive so that, over time, almost the entire east coast of Sumatra will consist of unproductive land that will become frequently flooded," Mr Silvius, programme head for climate-smart land use, told The Straits Times. "That means the livelihoods of the local communities will be jeopardised, industrial plantations will not be possible any more."
Sumatra's forest cover has plunged to less than 30 per cent. And nowhere has the loss been greater than the peatland-rich provinces of Riau, Jambi and South Sumatra, where vast oil palm and pulpwood plantations now occupy the areas where dense peat swamp jungles once stood.
"We're talking about four (million) or five million hectares," Mr Silvius said, when asked how much land could be lost due to peatland clearance in eastern Sumatra, an area about the size of Switzerland.
"It's not something just of the future. We already see it happening. Large areas of palm oil plantations are being flooded in Dumai in northern Riau."
Some areas, such as the Kampar Peninsula in Riau, could sink into the sea within decades unless businesses change the way they use peatlands.
Mr Silvius started studying Sumatra's peat swamp forests in the 1980s and saw their rapid deforestation over the next two decades.
To stop the deforestation and damage to the land, he said, the Indonesian government should stop issuing licences immediately to companies wanting to develop peatlands and start quickly to restore damaged areas, such as by re-wetting them.
Indonesia's peatlands are crucial because they are rich in plant and animal species and because they are one of the world's greatest storehouses of carbon. That carbon, in the form of leaf litter, dead trees and other material, builds up over thousands of years into vast peat domes that can be up to 20m high.
The carbon is trapped because the domes are filled with water, like a sponge, and don't degrade. Clearing and draining the peat using deep drainage canals quickly releases the water and the peat dries out, releasing large amounts of carbon dioxide, a powerful greenhouse gas. Over time, the peatlands subside as they dry out, creating huge areas ripe for fires.
Subsidence can be about 1m in the first year after clearing and digging drainage canals and about 5cm a year afterwards. Eventually, the land becomes vulnerable to water intrusion from the sea or rivers during the wet season, flooding large areas of plantations. As the subsidence continues, the flooding gets worse.
The situation is no better in Kalimantan or Sarawak, in Malaysia.
A study by Dutch institute Deltares, commissioned by Wetlands International, with results released in May, focused on how deforestation and drainage of tropical peatlands in Sarawak leads to subsidence.
The study focused on 850,000ha in the Rajang River Delta.
From 2000 to last year, oil palm plantations increased from 6 per cent to 47 per cent of the delta's land area, while the area of swamp forest decreased from 56 per cent to less than 16 per cent, the study says. The remaining area is also mostly drained, meaning that the entire area is now subsiding, it found.
The researchers, using a conservative rate of subsidence of 3.5cm a year, estimated that flood risk was already high in the area, affecting 29 per cent of plantations by 2009.
This was projected to rise to 42 per cent in 25 years, 56 per cent in 50 years and 82 per cent in 100 years. "It is predicted that at some point, oil palm production will have to be abandoned," the study concluded.
The threat from prolonged flooding has alarmed some companies fearing the loss of plantations, which are major assets.
Asia Pulp & Paper, Indonesia's biggest pulp and paper firm, has large concession areas on peatlands, particularly in Sumatra. APP recently commissioned Deltares to carry out what the company says is the largest mapping exercise for tropical peatlands using LiDAR equipment placed on aircraft. LiDAR uses pulsed laser beams to create three-dimensional maps of the earth's surface and vegetation.
Deltares will create a map covering about 4.5 million ha, or about a quarter of all Indonesian peatlands, where APP's suppliers are located. The information will help APP craft a new set of policies on improving management of peatlands in its concessions that the company hopes other land owners will also follow.
Better peatland management can reduce the risk of fires and slow the rate of subsidence. It should also involve restoring and protecting threatened deep-peat areas.
As part of its new peatlands best-practice programme, APP has pledged to retire 7,000ha of active plantations in deep peatlands, where the need for urgent restoration efforts was identified.
NGOs such as WWF and Wetlands applauded the announcement but said much more needed to be done to halt and reverse decades of deforestation and damage to millions of hectares of peatlands by plantation companies.
Mr Silvius said blocking of drainage canals and re-wetting drained peat areas and replanting them with native vegetation are part of the solution. Paludiculture, in which farmers earn an income from crops that flourish in water-logged soil, such as sago palm or illipe nut, is another solution but requires a radical change in thinking and political backing on how to develop these wetlands.
As for APP, the LiDAR study results could be a shock for them and other firms, he said.
"I think it is the first time a company is taking a step like that to look seriously at the sustainability issue. But I think the conclusions are going to be kind of shocking for them because most of their areas will prove to be totally unsustainable in the long term."