Climate change is increasing the severity of El Niño-driven fire weather across rapidly degrading peatlands and forests in Indonesia

In Between August and October 2026, western Indonesia experienced prevalent fire activity throughout an extremely hot and dry season, accompanying a strong El Niño occasion. Historically, El Niño has actually been highly connected with serious fire seasons in Indonesia, with the significant occasions of 1997 and 2015 both characterised by extremely high fire activity(ABC News, 2026. The 2026 fire season likewise accompanied record-breaking temperature level extremes and traditionally low seasonal rains, producing especially dry conditions throughout the area(Reuters, 2026.

Throughout the season, fires were focused especially in Sumatra and Kalimantan, with West and Central Kalimantan amongst the worst-affected areas. By September 2026, roughly 1,9 million hectares had actually burned nationwide, making 2026 among Indonesia’s worst fire seasons given that 2015 (Nusantaras Atlas, 2026. By mid-October, Central Kalimantan and South Sumatra represented the biggest shares of nationwide fire emissions(Katadata, 2026.

The fires had substantial ecological and social effects throughout Indonesia and neighbouring nations. By November, authorities had actually reported over 400,000 breathing infections connected with the fires (Antara, 2026with an approximated 12.5 million individuals exposed to haze throughout Indonesia, Malaysia, Singapore, and Timor-Leste (BBC, 2026.; The Straits Times, 2026. Smoke spread throughout Southeast Asia, impacting air quality in Malaysia, Singapore and the Philippines, triggering school closures and interfering with transportation, consisting of flights in Kalimantan ( ABC News, 2026Associated Press, 2026. By October, the fires had actually likewise added to significant greenhouse gas emissions, with 2026 emissions approaching levels tape-recorded throughout the serious 2015 fire season (Carbon Brief, 2026.

Researchers from Indonesia, the United States, the Netherlands, Sweden and the United Kingdom worked together to evaluate to what degree human-induced environment modification modified the possibility and strength of the climate condition at the time of the fires, and how the conditions will be impacted with additional warming. We concentrate on 3 areas on Borneo, Sumatra and Java(blue lays out, Fig. 1 )and 3 various variables to record different elements of the severe fires: (1)VPDx7x, which is the yearly optimum of the 7-day rolling average of day-to-day optimum vapour pressure deficit (VPD ). It is utilized in environment and wildfire-risk analysis to determine continual durations of hot, dry air. (2)the low rainfall throughout the July to October season, computed as the rainfall overalls of that season; and (3 )the August to October seasonal temperature levels. Provided the strong El Nino conditions, we examine both the function of environment modification and El Nino, utilizing the Relative Oceanic Niño Index (RONI). As the arise from all 3 areas are really comparable, we integrate them for the mathematical analysis.

Figure 1: PM2.5 (particle matter less than 2.5 µm in size from August-October 2026, sourced from GFAS1.4)emissions this fire season– related to greater health effects from smoke.

Main Findings

• The fires have actually burnt 1,9 million hectares of land, however effects reach far beyond the places of the fires themselves. Associated smoke impacted 12.5 million individuals throughout Indonesia, Singapore, Malaysia, and Timor-Leste. and added to 400,000 cases of breathing infections in Indonesia alone. Wildfires can trigger extreme and typically postponed health effects varying from problem breathing to heart attack. Intensifying vulnerabilities(e.g. pre-existing conditions, socioeconomics)and concurrent severe heat occasions, as happened this year, can increase the possibility of unfavorable health results.
• The wildfires have actually likewise damaged orangutan environments, limiting access to food and requiring seriously threatened orangutans into plantations and settlements, increasing human-wildlife dispute. In Java, fires harmed environments of other threatened types such as the Sunda pangolin and Javan leopard.
• Logging, logging and agroforestry growth have actually considerably decreased Indonesia’s tropical and peat overload forests, and are connected with fire usage for land clearance, while peatland drain increases fire vulnerability by drying carbon-rich peat. In between 1990 and 2010, peat overload forest cover decreased by roughly 45%in Borneo and 63%in Sumatra, with an additional 1.4 million hectares of forest on peatlands lost throughout Indonesia in between 2009 and 2019.
• All 3 areas evaluated reveal an extremely comparable action to ENSO, and while they are various with regard to plants, there are no Peatlands on Java, qualitatively the fire climate condition are extremely comparable. We for that reason integrate the 3 areas in the analysis listed below.
• Both jungle and peat land fires are extremely dry spell driven, and to examine these conditions we took a look at the July to October rains amounts to that managed fire season wetness supply. The other part of the seasonal dry spell is brought by warm, drying conditions. We evaluated the primary contribution of this through fire season temperature levels. In addition, we likewise evaluate VPD7x, which characterises short-term hot-dry occasions that frequently result in a fire beginning. All 3 steps are affected by ENSO and environment modification, while the ENSO signal controls in rains and has to do with the very same size as the environment modification signal in VPD7x, human-induced environment modification is without a doubt the most significant factor to this year’s seasonal temperature levels.
• Rainfall in observation datasets revealed an extremely strong relationship with ENSO, with the present El Niño approximated to have actually reduced the strength of this year’s seasonal rains by about 50 %. Human triggered environment modification likewise reveals an emerging reducing result on this year’s rains of about a 15%decrease in rains.
• Environment designs likewise represent the strong result of El Niño, however do disappoint the environment modification reaction that we see in observations.
• When examining seasonal temperature levels, we discover broad contract in between observations and environment designs. The evaluation reveals that environment modification has actually driven a significant boost in temperature levels by a number of orders of magnitude in probability and about 1.6 ° C in strength, while ENSO has actually had a smaller sized increasing impact, however constant in observations and designs, of about an aspect 11 and 0.3 ° C in strength. Therefore, for temperature levels we discover a little impact of the existing El Nino however a huge boost in the possibility and strength of 2026-like conditions attributable to human-induced environment modification.
• Fire activity in plant life reacts highly to short-term hot-dry extremes. The 7-day optimum VPD return duration price quotes recommend that the conditions observed in August– October 2026 are reasonably typical under comparable ENSO conditions. Observations and environment designs broadly concur, however designs reveal general a little smaller sized patterns. Integrating both designs and observations we discover that these conditions have actually ended up being around 3 times most likely due to human-induced warming, with VPD strength increasing by around 0.4 kPa. The continuous El Niño likewise increased the probability of these conditions by around 5 times, with VPD strength increasing by around 0.6 kPa. These are conservative numbers as they likewise consist of designs that do not represent the ENSO index well.
• The contribution of El Niño and environment modification to increasing the intensity of fire weather condition in Indonesia likewise implies that these conditions are progressively foreseeable, producing a chance for proactive threat decrease procedures. Minimizing landscape fire threat includes dealing with the conditions that add to fire ignition and spread, especially in drained pipes peatlands and broken down forests. Pertinent steps consist of peatland repair and conservation and keeping greater water level( e.g., obstructing canals, decreasing drain, and so on), securing staying forest locations, minimizing logging and incentivising land-management practices that decrease dependence on burning. While these procedures would currently minimize smoke contamination, extra concerns might consist of enhancing air quality tracking and public health cautions along with procedures to restrict smoke direct exposure and secure susceptible populations, especially throughout serious haze episodes.