The Rainforest is on fire! – Assessing the impact of peatland fires on human health in a changing climate

Scientific Background and Motivation

Every year, during the dry season, much of Indonesian Borneo experiences major wildfires often ignited by major agricultural burning of the peatlands to clear land for the production of pulp, paper and palm oil. In El Niño years the western Pacific experiences exceptionally dryer conditions, the water table drops and the peatlands dry out more than usual and this exacerbates the intensity of the burning and forest fires. This produces massive quantities of greenhouse gases (GHGs) representing a permanent loss of carbon to the atmosphere and generate smoke-laden air with an air quality considered extremely hazardous to human health. In addition to the emission of GHGs, extremely high levels of particulate material is produced by the burning, these particles can travel deep into the bronchial tubes in the lungs and cause breathing and heart problems. Given the scale of the health threat that PM2.5 pose, the WHO in 2021 described air pollution as “one of the biggest environmental threats to human health” and issued new air quality guidelines.

Fire (MODIS) Comparison of 2015 (El Nino) to 2012 (La Nina)

This all has atmospheric chemistry and air quality (AQ) impacts across the majority of the nine other ASEAN (Association of Southeast Asian Nations) member states in addition to Indonesia. In 2021 the World Health Organisation described air pollution as “one of the biggest environmental threats to human health” and issued new air quality guidelines. During the last El Niño in 2015, Indonesia, Singapore and Malaysia choked under a thick haze of wildfire smoke caused by the annual fire season closing schools, disrupting transport, including the closure of some airports, and half a million cases of acute respiratory infection were recorded between July and December.

In summer 2023 a positive El Niño was declared by NOAA, so we are expecting another severe fire season and some researchers think it might extend to impact the 2024-25 season. Launched in May 2020, and funded by UK Research and Innovation through the Global Challenges Research Fund, and the International Climate Fund, the Kalimantan Lestari (KaLi) project, deployed a network of air quality (PM2.5) sensors in a heavily fire-affected region in the south of Central Kalimantan province, some are visible providing a live datafeed. The focal area includes the provincial capital Palangka Raya with an urban population (~300,000) and the rural areas. A network of indoor and outdoor sensors was installed as well as local residents being equipped with mobile sensors to assess personal exposure. We anticipate that this initial exploratory observational period will be extended beyond the current El Niño cycle to allow us to characterise “low fire” exposure during the wet season. The aim is to assess an initial health impact on local populations using WRF-Chem, which is a state-of-the-art high resolution regional atmospheric transport model (ACTM).

Huge numbers of fires across southern Borneo with large plumes of smoke clearly visible
Extremely high PM2.5 levels (Purpleair) downwind of large fire clusters (NASA MODIS)

Project Objectives.

  1. This new project will build upon this opportunistic work which was added to the KaLi project to study the impact of the current positive phase El Niño, subsequent data collection and modelling will allow us to ascertain the impact of the El Niño on the regional haze and the associated health impacts.
  2. We have a new collaboration with Nafas, an organisation who operate a large network of particulate pollution sensors on the adjacent island of Java, alongside an ever-expanding network of low-cost sensors across the region. In combination with high resolution (1 km) population deprivation indices for Java this data can be used to develop health impacts at this resolution for a highly populated region.
  3. Previous work (Kiely et al) determined the health impacts driven by particulate pollution in the region over a 10-year period after incorporating peat burning emissions into the FINN fire emissions dataset. Using this revised emissions data we will build upon the work of Kiely and begin to account for real-world exposure using the data collected from the network we have deployed. In particular details of the exposure across the different socioeconomic groups will be used to refine the original health impact assessment whereas previous work only considered a blanket exposure across the whole population. This approach has not previously been done, bringing together a high resolution model with socio-economic exposure grouping coupled to observational datasets. We can take this further to estimate the economic impacts by country/region using the health impact results. This work can be expanded to higher resolution (10 km grid) for small areas such as East Kalimantan, which is currently proposed as the location of the new capital city.
  4. Traditionally heavy haze events have resulted in the closure of schools and it is not clear if domestic exposure is, in fact, higher than that in the school classroom. During a period of fieldwork, we will deploy sensors into school settings to determine the differences between home and school environments. It is expected that there will be some variation of this across different socioeconomic groups.


Kiely L, Spracklen DV, Wiedinmyer C, Conibear L, Reddington CL, Arnold SR, Knote C, Khan MF, Latif MT, Syaufina L, Adrianto HA. 2020. Air quality and health impacts of vegetation and peat fires in Equatorial Asia during 2004–2015. Environmental Research Letters. 15(9)

Graham AM, Pringle KJ, Pope RJ, Arnold SR, Conibear LA, Burns H, Rigby R, Borchers‐Arriagada N, Butt EW, Kiely L, Reddington C, Spracklen DV, Woodhouse MT, Knote C, McQuaid JB. 2021. Impact of the 2019/2020 Australian Megafires on Air Quality and Health. GeoHealth. 5(10)  

Reddington CL, Conibear L, Robinson S, Knote C, Arnold SR, Spracklen DV. 2021. Air Pollution from Forest and Vegetation Fires in Southeast Asia Disproportionately Impacts the Poor. GeoHealth. 5(9)

Crippa P, Castruccio S, Archer-Nicholls S, Lebron GB, Kuwata M, Thota A, Sumin S, Butt E, Wiedinmyer C, Spracklen DV. 2016. Population exposure to hazardous air quality due to the 2015 fires in Equatorial Asia. Scientific Reports. 6

Kiely, L, 2019, Indonesian fires and haze, University of Leeds and UBoC