The ground itself is on fire.

Most of what burns around Palangkaraya is not forest in the usual sense. It is gambut — peat: thousands of years of waterlogged plant matter, packed metres deep. While wet, it is almost fireproof. Drain it, and it becomes fuel.

That is what happened. In the 1990s a vast drainage scheme cut canals through the peat swamp of Central Kalimantan to grow rice that never grew. The land dried, and it has been catching light every dry season since. Those canals still drain water out of the ground today.

Why peat fires are different

What the haze does to a body

PM2.5 is small enough to cross from the lung into the bloodstream. Over a haze season it inflames airways, triggers asthma and acute respiratory infection, strains the heart, and is linked to low birth weight and stunted lung development in children. During the worst episodes, readings in Palangkaraya have been reported at many times the “hazardous” threshold, and schools and flights stop. Children, the elderly and pregnant women are the most vulnerable.

Fires also release carbon that peat locked away for millennia. Indonesian peat fires are among the largest single sources of seasonal greenhouse emissions on the planet, in dry years rivalling the daily output of entire industrial economies.