Wildfire smoke could have lasting effects for endangered orangutans
Indonesia’s peatland forests burn every year, producing toxic smoke that can cover a very large region, particularly during El Niño drought years. The resulting air pollution has major health consequences for humans in adjacent cities and towns, but little is known about how this haze affects the wildlife inhabiting these burning forests. Researchers from Rutgers University in the U.S. and Universitas Nasional in Indonesia collected behavioral data and urine samples from wild orangutans in Borneo to measure their short- and long-term responses to the 2015 El Niño-driven wildfires. Their work, published in Scientific Reports, found that, despite making energy-conserving changes to their behavioral patterns, orangutans needed to burn fat to meet their energy needs in the months following the fires. This research highlights the potential for lasting health consequences of prolonged and repeated exposure to hazardous smoke for both humans and wildlife, and identifies an additional conservation threat to critically endangered orangutan populations.
Soil analyses suggest that wildfires have occurred in Borneo for millennia, but have become increasingly frequent and intense in recent decades due to deforestation and draining of peatlands. In 2015, Indonesia experienced the most severe fire activity and smoke pollution on record since the disastrous wildfires during the 1997 El Niño droughts burned some 24,000 km2 of peatlands (12% of total peat area). Peatland fires not only destroy forest habitats, but also release greenhouse gases and produce hazardous particulate matter, the leading cause of worldwide pollution-related mortality. Two independent studies estimated that the 2015 haze caused somewhere between 12,000 and 100,000 premature human deaths, but there has been very little research into the effects on wildlife populations inhabiting these burning habitats.
Critically Endangered orangutans are known as “indicator species” because their health and behavior reflect or indicate the quality of their environments. For instance, when their habitats are disturbed or calorie rich fruit – is scarce, Bornean orangutans conserve energy by decreasing their activity levels and catabolize fat reserves to produce energy. Yet we lack a clear understanding of how these endangered apes respond to peatland fires and smoke exposure.
Between March 2015 and January 2016, Dr. Wendy Erb of Rutgers University and the Tuanan research team collected data on adult male orangutans’ at the Tuanan research station in Central Kalimantan, Indonesia. The team observed the orangutans’ feeding and activity throughout the day, and collected their urine each morning to test for ketones that appear when orangutans are burning fat. During the fire season (August 7 through November 6, 2015), NASA satellites detected 465 fire hotspots within a 10-km radius of Tuanan. Air quality – documented using concentrations of particulate matter – was very poor during this period, at times exceeding the Clean Air Act’s standard for environmental and public health more than 12-fold. Erb looked for changes in the orangutans during and after the forest fires to measure their responses to this unhealthy smoke pollution. “As the health consequences for humans are well documented and include asthma, heart attack, and even early death”, said Erb, “we were interested in looking for clues about how the this toxic air might be affecting the orangutans, too.”
Erb was surprised to find that there were very few changes in the orangutans’ behavior or condition during the smoke period, but admits that she can’t conclude there were not immediate responses during the fires. “Unfortunately, our research team had to put down our binoculars and pick up fire hoses for a month as the fires encroached into the study area and we worked tirelessly to protect the forest and community from the spreading blaze.” She says it’s very possible that the orangutans adjusted their behavior duding that month of peak fire and smoke, but they can’t show that with this data set. However, in the weeks following the fires, orangutans reduced their activities and increased the number of calories they consumed. “After the fires, the orangutans showed behavioral changes similar to what is often observed in disturbed areas or during episodes of fruit scarcity, except they were eating more calories, not less.” Despite the fact that they were eating more and moving less, orangutans were still burning fat – indicating that they had somehow increased their energy expenditure. Humans exposed to high levels of particulate matter during the 1997 peatland fires showed signs of inflammation, an immune response that increases energy expenditure and leads to weight loss in humans. Erb and her team think it’s possible that orangutans are responding to the air pollution in a similar way, and they plan to investigate this possibility in the near future by examining urinary markers of inflammation and stress in these same samples.
“This research is unique in that Dr. Erb has carefully examined the interactions between smoke pollution and orangutan health during the 2015 fires, something that has not been considered for long-term conservation plans in these peatland habitats. In the 15 years we have worked at Tuanan, the 2015 fires had the largest impact on this forest and presumably the animals within this peatland habitat”, said co-author Dr. Erin Vogel, director of the Orangutan Nutritional and Health Project at Tuanan and an Associate Professor at Rutgers University. “From this research, it is clear we have to further explore how these fires may be affecting the long-term health of these critically endangered animals”.
The unexpected loss of nearly 100,000 Bornean orangutans from intact forests in Kalimantan between 1999 and 2015 indicates habitat loss alone is not driving this Critically Endangered species’ declines. Increasingly frequent exposure to toxic smoke could have severe consequences for orangutans and other human and non-human animals, and this research highlights the urgent need to understand the long-term and indirect impacts of Indonesia’s peatland fires, beyond the immediate loss of forests and their inhabitants.
Materials provided by Wendy M. Erb, Ph.D.
Erb WM, EJ Barrow, AN Hofner, SS Utami Atmoko, ER Vogel. “Wildfire smoke impacts activity and energetics of wild Bornean orangutans” Scientific Reports, 2018. 10.1038/s41598-018-25847-1
CONTACT INFORMATION: Corresponding author: Wendy M. Erb, Ph.D.,