In May and June of most years, NASA satellites typically begin to detect large numbers of wildland fires throughout the Top End and Arnhem Land regions of Australia’s Northern Territory. On some days, especially in the afternoon, the blazes can resemble sizable wildfires in satellite imagery, spreading widely and producing expansive smoke plumes.

That was the case when NASA’s Aqua satellite acquired this image of smoke and fires on the afternoon of May 28, 2026. Often, however, fires burning in this area look smaller and less imposing. In the mornings just a few days earlier and later, for instance, NASA satellites detected little smoke despite observing many thermal anomalies, or hotspots, that indicated fire activity.

The pattern of burning, location, and timing are consistent with prescribed fires lit intentionally to manage the landscape. Land managers tend to light fires in the morning, and smoke builds over the course of the day. The process sometimes creates sizable plumes when there are updrafts and winds of moderate strength that carry smoke away from the fires, as happened on May 28 and again on June 2. The fires typically burn through the fire-adapted grasses, underbrush, and scattered trees in the region’s tropical savanna ecosystems.

Over the past few decades, the region’s land managers have combined deep-rooted Indigenous land management practices and modern technologies to establish large-scale landscape management programs such as the West Arnhem Land Fire Abatement project and Arnhem Land Fire Abatement. The goal of such efforts is to intentionally burn some of the savanna underbrush to create firebreaks and reduce fuel loads early in the dry season, reducing more destructive and emissions-intensive fires later in the season. The dry season generally begins in May and extends through September, according to Australia’s Bureau of Meteorology.

While research is ongoing, there are signs that the prescribed burning efforts are having the intended effect. Analysis of satellite observations of the fires suggests that prescribed burning efforts have shifted fire activity from late to early in the dry season, leading to a reduction in high-intensity fires and emissions.

NASA Earth Observatory image by Michala Garrison, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview. Story by Adam Voiland.

References & Resources

• Ansell, J., et al. (2020) Contemporary Aboriginal savanna burning projects in Arnhem Land: a regional description and analysis of the fire management aspirations of Traditional Owners. International Journal of Wildland Fire, 29(5), 371–385.
• Arnhem Land Fire Abatement (2026) Our Projects. Accessed June 4, 2026.
• Carbon Market Institute (2026) West Arnhem Land Fire Abatement (WALFA) Project. Accessed June 4, 2026.
• Edwards, A., et al. (2021) Transforming fire management in northern Australia through successful implementation of savanna burning emissions reductions projects. Journal of Environmental Management, 290, 112568.
• Evans, J. & Russell-Smith, J. (2020) Delivering effective savanna fire management for defined biodiversity conservation outcomes: an Arnhem Land case study. International Journal of Wildland Fire, 29(5), 386-400.
• NASA Earthdata, Questions About Real-Time (RT) and Ultra Real-Time (URT) Active Fire Data. Accessed June 4, 2026.
• NASA Fire Information for Resource Management System (2026, May 28) Fires/Hotspots. Accessed June 4, 2026.
• Russell-Smith, J., et al. (2026) Incentivising savanna fire management for emissions reduction, biodiversity conservation and community livelihood outcomes. International Journal of Wildland Fire, 35(4), 26039.

Wildfire smoke is stoking a new challenge for cleaner air. A NASA-supported study published Thursday found that, over the last decade, wildfires have worsened ground-level ozone pollution across much of the contiguous United States, creating unhealthy air far from active flames.

Wildfires have become an increasingly important contributor to ground-level ozone, or smog, across much of the United States, researchers report June 4 in the journal Science. Nationally, fires offset nearly four years’ worth of ozone-control gains, with larger setbacks in the West and Midwest.

Smoke often is associated with the soot, ash, and other fine particles that make the air look hazy. But wildfires also emit gases such as carbon monoxide, which can help form surface ozone in sunlight when other pollutants are present. Surface ozone is an invisible pollutant harmful to human health, plants, and crops. As smoke plumes travel and mix with other pollution, those reactions can drive ozone increases hundreds or even thousands of miles from active fires.

“NASA Earth observations, along with ground monitoring networks, help reveal air quality risks from wildfires that can cross state lines, giving air quality managers better decision-making information as wildfire smoke affects more communities,” said John Haynes, manager of NASA Earth Action’s Health and Air Quality program at the agency’s Headquarters in Washington. “This is a strong example of NASA science serving communities here in the U.S.”

Building a clearer ozone picture

High in the atmosphere, ozone shields Earth from harmful ultraviolet radiation. Near the ground, however, ozone can irritate lungs, worsen asthma and other respiratory diseases, and increase health risks for children, older adults, outdoor workers, and people with existing health conditions.

To track surface ozone changes, researchers turned to deep learning, a form of artificial intelligence that finds patterns across large datasets. They used it to build a first-of-its-kind dataset estimating daily surface ozone from 2003 to 2024 on a kilometer-by-kilometer grid — about 0.6 miles on each side — across the contiguous U.S. The work received support from NASA’s Health and Air Quality program and other NASA grants.

The scientists combined data from about 1,000 ground-based air quality stations with atmospheric model data, weather information, wildfire pollution data, and satellite-derived information, including products from the Visible Infrared Imaging Radiometer Suite (VIIRS) and the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments.

Their analysis revealed two distinct periods. From 2003 to 2015, U.S. ground-level ozone generally declined as emissions of ozone-forming pollutants decreased. After 2015, however, those gains slowed or reversed in many places. By comparing estimated ozone levels with scenarios that removed wildfire influence, the researchers found that pollution from wildfires was a main factor in that shift.

Without the wildfire contribution, ground-level ozone in the Midwest, for example, would likely have continued to decline. Instead, wildfires erased about 5.3 years’ worth of ozone-control progress since 2015.

“People in the Midwest may think fires burning far away will not affect them,” said the study’s corresponding author Jun Wang, an atmospheric scientist at the University of Iowa in Iowa City. “But once wildfire pollution is in the air, it can move across regions. Pollution from one place can affect air quality in another.”

Measuring the health toll

The study also found that wildfire-driven ozone increased exposure to unhealthy air and likely contributed to premature deaths. Premature deaths associated with long-term wildfire-related ozone exposure in the U.S. increased by an estimated 318 deaths per year after 2013, with the post-2013 average 46% higher than in the previous decade. The researchers calculated premature deaths using average lifespan, ozone exposure estimates, and population density.

The 2023 Canadian wildfires showed how widely those risks can spread, with smoke-driven ozone increases stretching across the Midwest and into parts of the Northeast and South. Overall, from 2022 to 2024, wildfires exposed an additional 43 million people in the U.S. to conditions that did not meet current federal air quality standards for ozone, the researchers estimated.

Capturing that national picture is difficult from ground monitors alone. Ground monitors remain the backbone of U.S. air quality tracking, but they do not cover every community. NASA’s scientifically validated satellite observations and models help researchers and agencies see air quality patterns across states, regions, and fire seasons.

That broader air quality work includes newer missions such as TEMPO (Tropospheric Emissions: Monitoring of Pollution). Launched in 2023, TEMPO is NASA’s first mission to use a space-based spectrometer to provide hourly daytime measurements of air quality over North America. Its view is sharp enough to distinguish pollution patterns, including surface ozone, across areas only a few square miles wide, a major improvement over earlier satellites.

Together, these capabilities help researchers and agencies see smoke-related ozone patterns that might otherwise be harder to detect, especially in rural and remote areas.

The work also points toward a practical use of NASA science during fire season. Wang’s team has used NASA support to develop FireAQ, a decision-support system that brings satellite observations, model forecasts, and fire and aerosol products into weekly briefings with state and local air quality officials. The goal is to help officials see where smoke-related pollution may move next and give communities better information.

Severe, hard-to-control blazes in densely populated areas like Los Angeles drove the year’s record losses.

Severe, hard-to-control blazes in densely populated areas like Los Angeles drove the year’s record losses.

© Loren Elliott for The New York Times