Global Forest Watch found 3,101 fires in the Javanese province.

‘There have always been forest and peat fires in Indonesia going back to the pre-colonial period,’ says Dr Robert Field, a research scientist at Columbia University’s NASA Goddard Institute. ‘At some point during the 20th century this accelerated as the land use became more intense. The burning rate in Indonesia is most severe in Sumatra, and southern Kalimantan. In Sumatra it has been developed more intensely and for longer. The events there have been happening since the 1960s.’

The reason behind the fires is a shift from subsistence agriculture in small fields to deforestation for large plantations. Fire is used to clear agricultural debris. Problems start when fires get out of control. During many years, it’s not a big problem as monsoon rain ensures the fires die down. But it becomes exacerbated during particularly dry years, according to Field.

Climate patterns play a key role as dry years happen mainly under El Niño conditions. The 1990s were a very active El Niño period and the forest fires that lasted during 1997–1998 were the biggest experienced by Indonesia during the entire 20th century. Over the last 15 years the fires have been less severe, but El Niño will be back.

‘Indonesia’s underground peat fires are unique, and this is where most of the smoke comes from,’ says Field. ‘At higher latitudes, such as the UK, peat fires can burn for years, but the water table comes back up and eventually extinguishes them.’ However, Indonesian fire fighters can’t extinguish the peat fires, and these can burn for months over a huge area before the water table rises.

Better seasonal forecasts may help. ‘Fifteen years ago this was not possible,’ says Field, ‘as forecasts were in their infancy, but they have since become a lot better and need to be part of any broader fire management policy.’

This story was published in the January 2015 edition of Geographical Magazine