October 4, 2015JPEG

Heavy smoke continues to pour from peat fires in Sumatra, Indonesia.

On October 4, 2015, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this image of smoke streaming over southern Sumatra. Red outlines indicate hot spots where the sensor detected unusually warm surface temperatures associated with fires. Gray smoke hovers over the island and has triggered air quality alerts and health warnings in Indonesia and neighboring countries.

Fires are a common occurrence in Sumatra in September and October because farmers engage in “slash and burn agriculture,” a technique that involves frequent burning of rainforest to clear the way for crops or grazing animals. In southern Sumatra, the intent is often to make room for new plantings of oil palm and acacia pulp.

Many of the fires are burning in areas with soils underlain with peat—a soil-like mixture of partly decayed plant material formed in wetlands. Peat fires tend to be difficult to extinguish, often smoldering under the surface for months. In comparison to other types of fires, peat fires release large amounts of greenhouse gases.

MODIS sensors on the Terra and Aqua satellites have detected fires burning in southern Sumatra since early September. Scientists monitoring the fires expect the fires to continue burning until the monsoon rains arrive at the end of October. However, they caution that the dry season could be unusually long in Indonesia this year because of the strong El Niño present in the Pacific Ocean.

1. Further Reading

2. Gaveau, D. et al (2014, May 7) Major atmospheric emissions from peat fires in Southeast Asia during non-drought years: evidence from the 2013 Sumatran fires. Scientific Reports, (4), 6112.
3. Motherboard (2015, January 12) How Climate Change is Fueling the World’s Longest-Burning Fires. Accessed October 8, 2015.
4. Washington University (2015, January 20) Peat fire emissions may shed light on climate change. Accessed October 8, 2015.
5. The New York Times (2015, October 8) Southeast Asia, Choking on Haze, Struggles for a Solution. Accessed October 8, 2015.
6. The New York Times (2010, August 20) The Fires Down Below. Accessed October 8, 2015.
7. Time (2015, October 8) Watch Eerie Drone Footage of Indonesia’s Vast Forest Fires. Accessed October 8, 2015.

NASA image Jeff Schmaltz (LANCE MODIS Rapid Response) and Adam Voiland (NASA Earth Observatory). Caption by Adam Voiland.