Human-Caused Wildfires Caused the Sky to Change Color in Indonesia

Surreal footage of a smoky red-orange haze blanketing parts of Indonesia went viral over the weekend, as the nation grapples with its worst forest fire season in years.

“This is Earth, not the planet Mars,” said Twitter user @zunishofiyn in a Saturday video post taken in Jambi province, which shows the landscape engulfed in a crimson tint.

The thick haze is fed by extensive human-made wildfires across Indonesia, which have already caused hundreds of thousands of respiratory ailments and have forced schools and airports to close.

“Unfortunately, once these fires have started, there is very little people can do to avoid exposure beyond staying indoors,” said Thomas Smith, an assistant professor in environmental geography at the London School of Economics, in an email. He noted that even this option “only offers limited protection, especially in poorer communities where buildings may not be adequately isolated from the outside air.”

The bizarre color observed in Jambi province is created by the filtering of the different wavelengths in sunlight through the haze, according to Koh Tieh Yong of the Singapore University of Social Sciences. Koh told the BBC that Rayleigh scattering, the phenomenon that makes the sky appear blue, can also cause air to appear orange or red as light bounces off an abnormally high abundance of small smoke particles in the air.

He also noted that much of the footage was captured around noon, when the Sun was directly overhead, which could have made the skies appear more brilliantly red.

But the hue also may appear enhanced in the viral photos of a blood-red sky, versus images depicting a more orange tint, because of standard digital camera settings.

“Verifying the colors in photographs taken during hazy conditions is difficult,” said Smith, due to “white balance” adjustments in most smartphone cameras. “When lighting conditions are particularly unusual (such as in thick smoke, or with theatre lighting for a more regular example), the colors in photographs can be distorted or over-saturated,” he explained.

“However,” he added, “having personally witnessed hazy conditions, it is common for the sky to turn a shade of orange when smoke is present in the atmosphere, during otherwise sunny conditions.”

Regardless of the sky’s particular hue, there’s no doubt that this is the worst air pollution that Indonesians have had to suffer through since the catastrophic fire season of 2015.

That year, fires scorched about 6.5 million acres of land and prompted the Indonesian government to declare a state of emergency in several provinces. Scientists estimated that smoke exposure from those fires caused at least 100,000 excess deaths across Indonesia, Malaysia, and Singapore, though the governments of the three nations disputed the results.

According to Smith, air quality measuring stations “are showing hazardous levels of air pollution, at levels that have not been seen since 2015 in many parts of Indonesia.”

Much like this year’s devastating fire season in the Amazon rainforest, the Indonesian fires are being set by humans using slash-and-burn techniques to clear forest land for agricultural use. In Brazil, rainforest is burned to make room for cattle ranches and crop farms, but in Indonesia, oil palm is the main industry driving the fires.

“In many places across Indonesia and Malaysia, the land is drained extensively for oil palm agriculture,” Smith said. “Finding alternatives to oil palm that require less drainage, and blocking drainage canals on abandoned land, will help stop these fires from spreading into peat soils and producing so much hazardous smoke.”

Climate change has also created drier conditions in forests, boosting the reach and intensity of fires, while the flames in turn belch out greenhouse gases, which fuels further climate change.

This feedback loop is especially troubling in Indonesia because of the nation’s widespread peatland environments, which are highly combustible during dry seasons and store disproportionate amounts of carbon. Though peatland only accounts for 3 percent of global land area, it is estimated to hold 21 percent of the world’s soil carbon, making Indonesia’s fires especially noxious on both local and planetary scales.

More than 800,000 acres of forest has been burned so far this season, and the fires are expected to rage until October or November. The smoky haze underscores the need for more stringent regulations against slash-and-burn practices and better policies to protect and restore Indonesia’s forests.

“To stop fires in the future, we need to avoid deforestation, particularly in lowland peatswamp forests,” Smith said.