Indonesia Wildfire Timeline 1997–2026: Why Peat Fires Keep Burning Underground

Start with the plain version: healthy tropical peat is essentially a waterlogged sponge of half-decomposed plants, built up over centuries. As long as the water table stays near the surface, that sponge cannot burn — there is no oxygen reaching the fuel.

Drain it — and Indonesia’s peatlands have been drained for decades, first for transmigration rice schemes, later for pulpwood and oil-palm plantations — and the top layers dry out. Dry peat is still mostly carbon, and now it has the one thing it was missing: air pockets. When a surface fire (almost always set deliberately, to clear land cheaply) reaches drained peat, it can ignite smouldering combustion: a slow, flameless burn similar to a cigarette ember, creeping through the dried peat at a fraction of a flaming fire’s speed but persisting far longer. It spreads sideways under vegetation and downward along root channels and cracks, which is the mechanism behind the “underground fire” people describe — not flames moving through open cavities, but combustion continuing where nobody can see it. This is why firefighters distinguish a peat fire from a normal wildfire, and why it demands a completely different response.

Two figures in this table actually point the other way from what the headlines suggest: the matched-week emissions figure (19.7 Mt in 2026 vs 21.7 Mt in 2015) and the hotspot count in isolation both need context. 2026’s early-September week is intense but still slightly below the same week in 2015. What has genuinely jumped is the rate — 273% above the seasonal average is a measure of how unusual this week is for 2026 itself, not a direct size comparison to 2015. Authorities’ own framing — “most intense fire season in 11 years” — is the accurate read: worse than every year since 2015, not worse than 2015 itself, at least not yet.

On burned area, two credible outlets published different 2026 year-to-date figures within days of each other in early September — one estimate near 300,000 hectares, another combining a confirmed ~202,000 hectares (January–July) with a separate August estimate of roughly 600,000 hectares. The gap likely comes down to cutoff date and methodology (confirmed burn-scar mapping vs. hotspot-based estimation), not one source being wrong. We’re showing both rather than picking whichever number is larger.

Fire-detecting satellites like NASA’s FIRMS (using MODIS and VIIRS sensors) work by scanning for thermal anomalies — patches of ground that are hotter than their surroundings. That works well for large, hot, flaming fires. It works less well for a peat fire smouldering a few centimetres under the surface, cooled and shrouded by everything above it, or obscured entirely by the thick smoke its own burning produces.

Mark Parrington, a senior scientist at the Copernicus Atmosphere Monitoring Service (CAMS), put it plainly: “One of the aspects with peat fires is if they’re burning at low temperatures or underground, they’d be below the detection limit of the sensors, which means we’re not actually seeing them.” That doesn’t mean satellites are useless — CAMS’ own emissions estimates, built from a mix of satellite fire radiative power and smoke-plume modelling, are exactly how outlets tracked the 19.7 Mt figure above. It means hotspot counts alone likely understate the true extent of a peat fire season, which is one reason officials increasingly report emissions and burned-area estimates alongside hotspot counts, not instead of them.

Indonesia’s peatlands are estimated to store somewhere between 13.6 and 40.5 gigatonnes of carbon, with a widely cited best estimate around 28.1 gigatonnes (Warren et al., Carbon Balance and Management, 2017, based on national peatland maps) — roughly 30% more carbon than sits in the biomass of all of Indonesia’s forests combined, and part of a global tropical peat carbon pool the same study puts near 75 gigatonnes. That carbon accumulated over centuries because waterlogged peat barely decomposes. Drain it and burn it, and that slow accumulation reverses in weeks, which is the real reason a peat fire matters far beyond the smoke it produces locally.

Indonesia’s response to 2015 was not cosmetic. The Peatland Restoration Agency (BRG), created by presidential regulation on 6 January 2016, was given a specific, measurable target: restore 2 million hectares of burned or degraded peatland within five years, mainly by rewetting — blocking drainage canals so the water table rises back toward the surface, plus revegetation and community-based fire prevention in the same priority provinces. In 2019, Indonesia made its moratorium on new permits to clear primary forest and peatland permanent rather than renewing it every few years. In 2020, BRG merged with a mangrove-restoration mandate to become BRGM, widening its scope.

Between 2016 and 2025, fire seasons were, on the whole, smaller than 1997, 2006 or 2015 — though separating the effect of restoration from the effect of several relatively wetter years in between is genuinely difficult, and independent researchers have flagged that as an open question rather than a settled win.

So why can severe peat fires still return?

1. Restoration covers a fraction of the problem. Indonesia has an estimated 15 million-plus hectares of peatland; a 2-million-hectare restoration target, even if fully met, leaves most peatland outside the program untouched or only partially rewetted.
2. Rewetted peat can still dry out. A strong enough drought, like the one building through 2026, lowers water tables faster than canal-blocking alone can compensate, especially at the edges of restored zones.
3. Ignition is still overwhelmingly human. Restoration changes how flammable the land is, not whether someone sets a fire on it — enforcement against illegal burning remains uneven, especially on smallholder and disputed land.
4. El Niño keeps returning on its own schedule. Restoration is a multi-decade project; El Niño droughts arrive every few years regardless of how that project is progressing, and 2026 is the first genuinely strong test since the reforms began.

The honest reading of 2026, based on verified data so far, is that the reforms are working as intended — slowing the crisis, not eliminating it — against a strengthening El Niño that is exactly the kind of stress test they were never going to fully survive untested.