Slowing the spread of wildfires

How human intervention is reversing a decades-old trend in Indonesia

Photo: iStock, Toa55

The average Canadian would likely be surprised to hear that, in some parts of the world, wildfire severity may actually be decreasing. That seems inconceivable given that wildfires in Canada have made more headlines in recent years than ever before: from the near-total destruction of Lytton, B.C., in 2021 to the Quebec fires of 2023 that darkened skies as far south as New York City. But by closely examining nearly 20 years of daily satellite imagery, Sean Sloan, Canada Research Chair in the Human Dimensions of Sustainability and Resilience at Vancouver Island University, has found that wildfire severity in equatorial Asia appears to be decreasing, likely as a result of human intervention.

“The story of diminishing wildfires is a reflection of land management,” he says. “As more landscapes are increasingly managed, more fires are suppressed or prevented. This is a story that’s not well documented in many places.”

A hopeful countertrend

Wildfires have been increasing in frequency and severity in many places around the world, largely due to the effects of climate change, which have produced hotter and drier summers. While we might assume human activity is making things worse, that may not always be the case. In some places—particularly the semi-arid savannah regions of Africa—increasingly expansive and intensive land management has led to fewer and less severe fires in naturally fire-prone areas, which, in turn, has produced an overall downward wildfire trend.

Typically, the opposite is true in humid, rain-forested biomes. There, human activity involves thinning and drying out naturally fire-resistant forests, making them more likely to burn. That’s exactly what was happening in Indonesia, where expanded oil palm farms and degraded peatlands were creating ideal burning conditions. With cyclical El Niño events leading to severe droughts about every five years, the resulting wildfires were becoming larger and more intense. The country has consistently registered the biggest tropical wildfire events since the 1970s.

But Sloan says recent, progressive changes to land management are now attenuating this historical trend.

“During El Niño events, the area burns like a tinder box,” says Sloan. “So, Indonesia seemed like the least likely place to observe a downward trend in fire severity. But when you look at the data correctly, the trend toward attenuating fire severity is solid.”

Humans can make a difference

Most fire data come from satellite imagery, providing a snapshot of burning and land cover at a given moment. Sloan’s research took a more granular look at this imagery, gathering, compiling and processing data on not just daily fire activity but also land use and precipitation. This enabled him to build a model to identify, classify and track discrete fire events in Indonesia from 2002 to 2019. He found that, when controlling for the relative dryness of a given fire season, fire severity actually trended downward during the study period.

Although his research was not intended to determine the causes of the trend, Sloan notes several key changes in how land is being managed in Indonesia that may have had an impact on fire severity. Increasingly, extensive and intensive farming activity has reduced the number of trees and brush on managed lands of mixed farm and forest cover, leaving less biomass to burn. At the same time, increased investment in land use naturally gives rise to increased fire suppression by landholders looking to protect their investments.

As well, In the wake of severe burning in 2015, the Indonesian government introduced strict new measures to improve fire management on managed lands. Also, a global downturn in the price of palm oil—combined with increasing government regulations on that industry—has likely resulted in the slowed expansion of oil palm farms across the country, which may have prevented burning at the levels seen historically.

“While the evidence isn’t strong enough to say for sure, the research does suggest that non-climatic factors—namely land management—are likely behind the attenuation of severe fire activity,” says Sloan.

The future of wildfires remains uncertain

Sloan’s work looks at large-scale change over decades and is therefore not directly applicable to policy developments. Nor can his findings from Indonesia be directly transferred to other regions that also experience wildfires—including Canada—as different social, climatic and forest-management contexts may yield different results. However, the findings may support the efficacy of fire suppression and prevention programs, suggesting that human behaviour can make a difference in wildfire intensity, even in the most fire-afflicted regions.

While there is further work that could be done to better understand the relationship between those behaviours and wildfires, Sloan believes it’s important to look for the hidden trends that may help provide a more complete picture of global events.

“I’m documenting the underappreciated aspects of these larger, mostly negative trends—the obscure countercurrents or the echoes to the more well-known booms,” he says. “These may offer a more positive outlook or a more thorough understanding of major environmental changes.”

Want to learn more?

To learn more about Sean Sloan’s research on wildfires and forest regeneration, see his Vancouver Island University faculty profile and read his paper, Declining severe fire activity on managed lands in Equatorial Asia.