The forests of the western Himalayas are usually ravaged by fires in the summer, but this year has been different. Just as temperatures started soaring, India went into a nationwide lockdown to contain COVID-19.
As the lockdown proceeded over a little less than 2 months, the number of forest fires in the Indian Himalayas dropped dramatically. Compared with numbers in previous years, about 80% fewer fires ignited in the region.
Researchers said the inadvertent experiment adds to evidence that humans are one of the main causes of forest fires in the region. They published their results online in Current Science in June.
Burning Mountain Forests
The westernmost portion of the Himalayan range stretches from Afghanistan into northern India. The northern slopes of the mountains are bare, but the southern slopes are rugged and heavily forested. Although these forests have regularly burned in major fires over the past century, fire incidences have been increasing since the 1990s, mainly due to human activities compounded by rising temperatures, say researchers. The Himalayan states of Sikkim, Uttarakhand, and Himachal Pradesh are the most affected by fire and have seen some of the worst fires in the past 2 decades, notably in 2016, with about 7,500 hectares of land ablaze.
Forest fires are most common in the months between March and June. Temperatures are high, and fuel in the form of dry leaves and twigs is just waiting for a spark to burst into flames.
Lightning often provides that spark. But so can a carelessly thrown still-glowing match or a poorly damped campfire.
“There is hardly any study which has been able to quantify the extent of the anthropogenic activity on the forest fire incidences across the world, as almost all ecosystems have a human footprint,” said Arijit Roy of the Indian Institute of Remote Sensing (IIRS) in Dehradun, the corresponding author of the study. Roy and his colleagues saw an opportunity to dig deeper into this question when India declared a complete lockdown to combat COVID-19.
Opportunity in the Lockdown
Because of the high prevalence of fires in Uttarakhand and Himachal Pradesh, researchers regularly monitor fire data in these regions via the Aqua and Terra satellites, delivered by NASA’s Fire Information for Resource Management System. Amitesh Gupta, also of the IIRS and lead author of the new study, was monitoring the data at the beginning of the lockdown when he noticed a sudden drop in the daily counts of fire points—the geospatial location data of fires obtained from the satellites—in late March and early April. Gupta kept an eye on the data, collected by the Moderate Resolution Imaging Spectroradiometer (MODIS).
Eventually, Gupta and his colleagues compiled the number of fire events in Uttarakhand and Himachal Pradesh between 24 March and 5 May, when India was under complete lockdown. In addition to fire data, they also included data obtained for vegetation cover, rainfall, and surface temperatures and mapped their results for the region.
They saw a striking drop of 83% in the number of fires during the lockdown compared with the average number of fire incidences over the past 15 years. “The scientific community had known about the anthropogenic impact on forest fire incidences. The surprising aspect was the extent of the impact,” said Roy.
With people and vehicles no longer moving around in the area, Roy said, the number of sparks igniting fires seems to have gone down. Some small fires may have been caused by people going into the forests for subsistence activities, such as collecting firewood and grazing cattle.
“Whether the majority of fires are caused by humans or lightning is a good question” and has not been investigated much, said Raman Sukumar, an ecologist at the Indian Institute of Science in Bangalore who was not part of the study. Sukumar said humans undoubtedly cause a major proportion of fires in these Himalayan forests, but he thinks that the proportion of natural versus human-set fires remains largely unknown.
Sukumar said other factors could explain the drop in fires, not just the absence of humans in the forests. For example, this year’s rainfall has been very high, about twice the average precipitation in the past 15 years. Any fuel should have been too wet to ignite, said Sukumar, which might have dampened the number of fires.
Roy said his team factored this possibility into their analysis. Even though rainfall was higher, the amount of moisture retained by the soil was the same as in the past 8 years. Furthermore, Roy said that data for the past 20 years showed that the number of fires was still 3 times lower this year than in previous years with similar precipitation levels.
Whether or not more rain played a role in the lower number of fires, Sukumar said, with fewer people in the woods, “the number of ignitions will certainly come down.”
—Lakshmi Supriya, Science Writer