Why are peat-swamp forests so vulnerable to fire?

Conservation Blog

The current intense dry season is leading to fires, across Borneo and Sumatra, which have taken hold in peatland areas. Logic might dictate that these areas should not be susceptible to fire: they are swamps, after all, swamps are by definition wet and wet things don’t burn, so surely peat swamps should be highly resistant to fire. Why on Earth, then, are fires currently raging throughout Borneo and Sumatra’s peatlands?

Peatland burning on the edge of the city of Palangkaraya (Indonesian Borneo) this month. Photo by Suzanne Turnock/OuTrop

The logic that peat-swamp forests should be wet and resistant to fire is entirely true, and historical evidence indeed suggests that fires in peatlands were very rare events up until just a few decades ago. The problem occurs when – yep, you guessed it – humans start disrupting natural processes.

Peat is formed under very wet conditions, when dead plant material is unable to decay in the flooded environment. This leads to a build-up of partially decomposed organic matter, which over time accumulates in peat domes, like the Sabangau Forest, OuTrop’s main research site. Here, the peat is around 26,000 years old and measures more than 12 metres deep in the centre. These peat domes act as a giant sponge, absorbing water to prevent floods during the wet season, and staying wet to prevent fire during the dry season. If buried over millennia, peat deposits become coal.

Peat-swamp should be wet and fire resistant, but due to human activities peat-swamps in Borneo and Sumatra are at risk from fires every year during the dry season. Photo by Chris Owen/OuTrop

Unfortunately, human use of peatlands typically involves peat drainage through man-made canals. This is usually done in an attempt to make the land more suitable for agriculture or habitation, but also for loggers to transport timber from inside the forest to processing points on rivers. The worst example is the failed Mega Rice Project of the mid-1990’s, which aimed to drain 1 million hectares of peatland in Central Kalimantan and convert it to rice production. The area now suffers from extensive fires each year, representing a true ecological catastrophe.

The ex-Mega Rice Project area burning in 2006. Photo by CIMTROP.

The problem is that, like coal, dry peat is highly flammable. This means that fire can easily take hold in areas of drained peatland and, once started, fires are incredibly difficult to extinguish as they burn underground.

Drainage of peatlands is the root cause of the current fire crisis in Indonesia, as this removes the natural protection from fire that intact peatlands receive.  Drought does, however, play an important role in determining the level of fire risk in a particular year, and this role will be examined in an upcoming blog post.

You can support OuTrop and local firefighting efforts in Borneo here.