Wildfire

• 1. Introduction

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  Wildfire is one of the oldest forces on Earth. Fossils of the giant fungi Prototaxites, preserved as charcoal and discovered in South Wales and Poland, push the first evidence of fire back to the Silurian period. And yet, for all that geological age, wildfires today are behaving differently than at any point in recorded human memory. A study published in Science Advances found that from 1975 to 2024, the annual potential burning hours for wildfires in North America rose by 36 percent. In 2020, the carbon released by California's wildfires alone was significantly larger than the state's total emissions from all other sources combined.

  How does an unplanned fire in a patch of dry grass become a force that shapes the atmosphere, contaminates drinking water, and restructures entire ecosystems? What makes some landscapes dependent on fire, while others are destroyed by it? And what happens when human decisions, from power lines to climate change to a century of fire suppression, tip a natural cycle into something far harder to control? Those are the questions this documentary will explore.

• 2. The Fire Triangle

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  Wood begins to release flammable gases when it reaches 230 degrees Celsius. At 380 degrees it smolders. At 590 degrees it ignites. But even before flames arrive, a wildfire front heats the surrounding air to 800 degrees Celsius, pre-drying the material ahead and allowing the fire to spread faster than it otherwise would.

  The spread is governed by fuel, terrain, and weather working together. Ground fires consume subterranean roots and buried organic matter, burning slowly by smoldering for days or even months. Peat fires in Kalimantan and Eastern Sumatra, Indonesia, are an example, the result of a riceland creation project that unintentionally drained and dried the peat. Surface fires burn at relatively lower temperatures, generally below 400 degrees Celsius, but steep slopes and wind can accelerate them sharply.

  Crown fires are the most dramatic category. Igniting at the canopy level, they depend on the density of suspended material, moisture content, and the ladder of smaller vegetation connecting the ground to the treetops. Invasive species such as kudzu and Old World climbing fern encourage exactly these ladder conditions by scaling trees and connecting fuel layers that would otherwise be separate.

  Once a fire is large enough, it begins to generate its own weather. Powerful updrafts draw in cooler air from surrounding areas, and great vertical differences in temperature and humidity can produce pyrocumulus clouds, strong winds, and fire whirls with the force of tornadoes at speeds of more than 80 kilometers per hour. In Australian bushfires, spot fires started by airborne embers have been recorded as far as 20 kilometers from the main fire front, leaping roads, rivers, and other barriers in a single bound.

• 3. Human Ignition

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  Over 85 percent of wildfires in the United States are started by human activity. The causes range from arson, which may account for more than 20 percent of human-caused fires, to equipment sparks from chainsaws, grinders, and mowers, to overhead power lines and campfires.

  In the tropics, farmers often practice slash-and-burn clearing during the dry season. In 2019, the fires in the Amazon rainforest were caused mainly by illegal logging. In that same year, extreme heat and dryness ignited massive wildfires across Siberia, Alaska, the Canary Islands, and Australia simultaneously.

  The relationship between arson and wildfires is more complicated than it might appear. During the 2019-20 Australian bushfire season, an independent study found that online bots and trolls were exaggerating the role of arson in those fires. In the 2023 Canadian wildfires, false claims of arson also gained traction on social media, though arson is generally not the main cause of wildfires in Canada. In California, roughly 6-10 percent of wildfires annually are attributed to arson.

  Coal seam fires add another dimension. They burn in the thousands around the world, in places such as Burning Mountain in New South Wales, Centralia in Pennsylvania, and several locations in China. These fires can flare up unexpectedly and ignite nearby flammable material, making them a persistent and often overlooked ignition risk. Since the mid-1980s, earlier snowmelt in the Western US has extended the fire season, lengthening the window during which all of these ignition sources intersect with dry and vulnerable landscapes.

• 4. Climate and the Feedback Loop

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  In the summer of 1974-1975, Australia suffered what was then its worst recorded wildfire, when 15 percent of the continent's land mass experienced extensive fire damage and an estimated 117 million hectares burned. That figure was surpassed in 2023, when 18 million hectares burned in Canada alone, with smoke affecting air quality and agricultural productivity thousands of kilometers away.

  Climate change drives this escalation through several interlocking mechanisms. Higher temperatures increase potential evapotranspiration, drying out vegetation and soil. Vapor pressure deficit, which worsens in a warming climate, amplifies fire risk further. Heat waves, droughts, and El Nino events lengthen the fire season, particularly in regions where snowpack is disappearing earlier in the year.

  The fires themselves then accelerate the process. Forest fires in Indonesia in 1997 were estimated to have released between 0.81 and 2.57 gigatonnes of CO2 into the atmosphere, representing between 13 and 40 percent of the annual global carbon dioxide emissions from burning fossil fuels at the time. In June and July of 2019 alone, fires in the Arctic emitted more than 140 megatons of carbon dioxide, an amount equivalent to the annual emissions of 36 million cars.

  Black carbon deposited on snow by wildfires compounds the warming effect. Research in 2007 found that black carbon in snow changed temperature three times more than atmospheric carbon dioxide, and that as much as 94 percent of Arctic warming may be caused by dark carbon on snow initiating melting. The Amazon, which holds an estimated 90 billion tons of carbon, faces the prospect that fires, drought, and human activity could damage or destroy more than half of the rainforest by 2030.

• 5. Ecosystems That Need Fire

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  Plant and animal species across most types of North American forests evolved alongside fire, and many of them depend on it to reproduce and grow. The heat from fire is necessary to the germination of certain seed types. High-severity wildfire creates what ecologists call complex early seral forest habitat, also known as snag forest habitat, where dead trees and open canopy produce conditions that often support higher species richness and diversity than unburned old forest.

  The paradox is that a century of wildfire suppression in Canada and the United States has created exactly the wrong conditions. By extinguishing lightning-caused fires, land managers allowed fuels to accumulate beyond what more frequent, lower-intensity fires would have left behind. The result is fewer fires but higher-severity ones capable of killing mature trees that would otherwise survive.

  Some ecosystems have been pushed too far in the opposite direction. The chaparral in southern California and lower-elevation deserts in the American Southwest are ordinarily fire-dependent, but increased fire frequency has upset their natural cycles, damaged native plant communities, and encouraged non-native weeds. Invasive species such as Lygodium microphyllum and Bromus tectorum grow rapidly in fire-damaged areas and, because they are highly flammable, increase future fire risk, creating a positive feedback loop that further alters native vegetation.

  Trees such as Eucalyptus, Pinus, and Sequoia appear to have benefited from fire-prone conditions over geological time, developing thick bark that allows them to survive fires that kill less-adapted species. Fire-stick farming, the careful and sustained use of fire practiced by Aboriginal Australians for centuries, has been employed in lands now protected by Kakadu National Park to encourage biodiversity, a reminder that managed fire and ecological health are not mutually exclusive.

• 6. Health Costs of Smoke

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  Between 80 and 90 percent of wildfire smoke, by mass, consists of particles 2.5 micrometers in diameter or smaller. Those fine particles are the principal health threat, alongside carbon monoxide. Ultrafine particles below 0.1 micrometer, a major component of wildfire smoke, enter the bloodstream more quickly and cause more severe inflammation and epithelial damage than larger particles.

  An observational study of smoke exposure from the 2007 San Diego wildfires found an increase in healthcare utilization and respiratory diagnoses, particularly asthma. Following the same year's California wildfires, high levels of lead, arsenic, cadmium, and copper were found in ash debris, prompting a national clean-up campaign. In the 2018 Camp Fire, which killed 85 people, lead levels at a nearby monitoring site in Chico increased by around 50 times in the hours following the fire, while zinc concentrations rose significantly in Modesto, 150 miles away.

  An estimated 46 million people were exposed to wildfire smoke in the Western United States alone from 2004 to 2009. Worldwide, an estimated 339,000 people die each year from the effects of wildfire smoke. The health effects extend beyond the immediate fire zone. Wildfire smoke can be transported intact for distances exceeding 1,600 kilometers, as revealed by satellite observation of smoke plumes, affecting air quality in regions with no direct connection to the fire.

  The projected toll continues to rise. The health effects of wildfire smoke, including worsening cardiovascular and respiratory conditions, already contribute to nearly 16,000 annual deaths, a figure expected to climb to 30,000 by 2050. The economic cost is projected to reach $240 billion annually by 2050, surpassing other climate-related damages. Pregnant women represent one of the less-discussed at-risk groups: mothers who were pregnant during California's 2003 Southern California wildfires gave birth to babies with a slightly reduced average birth weight compared to those not exposed.

• 7. Detection and Suppression

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  Fire lookout towers were used in the United States in the early 20th century, with reports sent by telephone, carrier pigeon, and heliograph. Aerial and land photography with instant cameras replaced them in the 1950s, until infrared scanning was developed for fire detection in the 1960s. Even then, early satellite-derived fire analyses were hand-drawn on maps at a remote site and sent via overnight mail to the fire manager. During the Yellowstone fires of 1988, a data station established in West Yellowstone allowed satellite-based fire information to reach managers in approximately four hours, which at the time was a significant advance.

  Modern detection now spans a range of technologies. The Department of Natural Resources signed a contract with PanoAI for the installation of 360-degree rapid-detection cameras around the Pacific Northwest, mounted on cell towers and capable of continuous monitoring of a 15-mile radius. Sensaio Tech, based in Brazil and Toronto, has released a sensor device that monitors 14 different variables including soil temperature and salinity, delivering live data through dashboard visualizations. Since 2021, NASA has provided active fire locations in near real-time via the Fire Information for Resource Management System, known as FIRMS.

  Suppression remains costly and dangerous. More than 99 percent of the approximately 10,000 new wildfires that start each year in the United States are contained, but those that escape under extreme weather conditions are difficult to stop without a change in the weather itself. In the United States, local, state, federal, and tribal agencies collectively spend tens of billions of dollars annually on suppression. The California U.S. Forest Service spends about $200 million per year suppressing 98 percent of fires, and up to $1 billion on the remaining 2 percent that escape initial attack and grow large.

  Between 2000 and 2016, more than 350 wildland firefighters died on-duty. The 1949 Mann Gulch fire in Montana remains one of the starkest examples of how quickly conditions can turn fatal: thirteen smokejumpers died when they lost communication, became disoriented, and were overtaken by the fire. Between 2001 and 2012, over 200 fatalities occurred among wildland firefighters, with a study tracking deaths from 1990 to 2006 finding that 21.9 percent resulted from heart attacks rather than direct flame exposure.

• 8. After the Fire

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  A 2003 wildfire in the North Yorkshire Moors burned off 2.5 square kilometers of heather and underlying peat layers. Afterward, wind erosion stripped the ash and exposed soil, revealing archaeological remains dating to 10,000 BC, a reminder that fire reshapes the landscape in ways that extend far beyond the immediate burn.

  Water contamination is one of the most persistent and least visible post-fire hazards. Hazardous waste-scale chemical contamination of buried water systems was first discovered in the United States in 2017, and has since been documented in Hawaii, Colorado, and Oregon. In Paradise, California, the 2018 Camp Fire caused more than $150 million in damage to the municipal drinking water system, requiring almost a year of work to decontaminate and repair. Researchers have estimated that, in worst-case scenarios, more than 286 days of constant flushing of a contaminated HDPE service line are needed to reduce benzene concentrations below safe drinking water limits.

  In Northern California, one mitigation approach has taken a decidedly low-technology form. Goat herds have been deployed in many communities to reduce fire fuels on the outskirts of settlements, with an estimated 60,000 to 80,000 goats employed in this role by 2024. Communities in the Philippines maintain fire lines 5 to 10 meters wide between forest and village, patrolled during dry seasons, another durable and inexpensive technique that has proven its value long before satellite monitoring or AI-based detection entered the picture. In Canada, by June 2025, 3.24 million hectares had already burned, setting the stage for a fire season that may again test the limits of every suppression tool available.