Using the visibility proxy, we show that large fire events have occurred in Sumatra at least since the 1960s, but in Kalimantan only since the 1980s, despite the occurrence of several severe droughts during 1960-1980. This increase in sensitivity of fires to drought in Kalimantan coincides with Indonesia's transmigration program and dramatic changes in land use. Our results show a non-linear relationship between rainfall and fire, whereby fire events occur only during years when rainfall falls below a certain threshold in combination with the presence of human land use. In Kalimantan, this drought is controlled primarily by sea-surface temperatures in the Pacific Ocean, whereas in Sumatra, they are controlled primarily by sea-surface temperatures in the Indian Ocean. Better understanding of these controls may help to predict future fire risk in Indonesia with changing climate and land use.