Indonesia's Haze Season Is Going To Get Worse

Rising global temperatures may increase the risk of forest fires in Indonesia, even during the rainy season, according to a new study published in the peer reviewed scientific journal Environmental Research Letters earlier this week.

Scientists from four different organizations conducted a study of Indonesia's annual forest fires, discovering that rising temperatures were playing a significant role in the rate of forest fires during the rainy season.

The study casts doubt on the common idea that the country's recent struggles with forest fires—and the choking haze they produce—were the result of droughts caused by the El Niño weather phenomenon alone. The country's haze crisis in 2015 came as the region experienced drier than normal conditions during an El Niño year. The droughts are expected to return this year, prompting government officials, wary of the country causing another regional crisis, to step-up fire prevention preparations.

El Niño-related droughts do increase the risk of forest fires during the dry season—when higher-than-normal temperatures have little impact on forest fire rates. A drought is a drought, regardless of how hot it gets.

"In other words, once droughts are established we should expect to see more fires regardless of temperature," the study's lead author Kátia Fernandes told Columbia University's Earth Institute.

But higher temperatures do cause problems during the rainy season, Fernandes explained.

"We know that El Niño events increase the likelihood of drought in Indonesia, and with that, the risk of wildfires," she said. "Uncontrolled fires, like those which occurred in 2015 and 1997-1998 can destroy vast swaths of diverse tropical forests, release billions of tons of carbon dioxide and create public-health emergencies across the region.

"The question we set out to investigate was whether other climate variables beside rainfall could be playing a role in determining the level of fire activity during times when seasonal droughts were not severe."

Why? Because sometimes forest fires defy easy explanations. In 2013, a spate of forest fires occurred in Sumatra when it wasn't all that dry. The scientists behind this study wanted to understand what else, aside from droughts, could cause the rate of forest fires to increase.

Temperature, it turns out, is the key. Higher temperatures increase evaporation rates and place new stress on plant life regardless of how much it rains. There is a risk of forest fires even in times of above-average rainfall, the reports authors found.

Why is this important? Because governments tend to prepare for forest fires ahead of the dry season only. It's important to have fire mitigation measures in place year-round, according to the results of the study.

"Efforts to prevent fires in Indonesia focus on drought years, and this may be addressing only part of the risk," Fernandes said. "Prevention and mitigation measures can benefit from a deeper understanding of how fire behave in non-drought conditions as well."

What's it mean for Indonesia? The study's rainfall projections show a relatively unchanged level of precipitation in the coming years. And El Niño is relatively predictable. But global temperatures are expected to increase, according to climate change data. This means higher risk of fires year-round and a fresh challenge for governments looking to head-off another crisis on the same level as 2015's haze.

Fernandes believes that so-called "mild fire seasons" are going to become a thing of the past.

"Temperatures are expected to continue increasing," she said. "So understanding temperature's effect on fire occurrence is going to be extremely relevant."