Human-Caused Wildfires: The Hidden Threat of Devastation

Wildfires Initiated by Routine Human Activities Are Frequently More Devastating

By Virginia Iglesias & The Conversation US

The subsequent essay is republished with authorization from The Conversation, a digital publication highlighting the latest discoveries.

Investigators are seeking to identify the triggers behind several wind-driven wildfires that have ravaged thousands of residences across the Los Angeles area in January 2025. Given the locations of the fires, and absence of lightning at that moment, it’s probable that utility infrastructure, alternative equipment, or human actions were implicated.

Wildfires in California have become increasingly devastating over recent years. Research conducted by my colleagues and myself indicates U.S. wildfires are as much as four times larger and three times more frequent than they were during the 1980s and ’90s. Rapidly advancing fires have proven particularly ruinous, accounting for 78% of destroyed structures and 61% of suppression expenses from 2001 to 2020.

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Lightning strikes are a regular cause of wildfires in the U.S., yet the majority of wildfires that jeopardize communities are ignited by human actions.

A malfunctioning power line sparked the fatal 2023 fire in Maui that devastated the town of Lahaina, Hawaii. Metal dragged by cars or lawn mowers can ignite fires. California’s largest fire in 2024 ignited when a man pushed a burning vehicle into a ravine near Chico. The fire obliterated more than 700 homes and structures.

What factors contribute to the destructiveness and containment difficulties of these wildfires?

The solution lies within a combination of wind velocity, shifting climate, historical land-management practices, and current human endeavors that are altering fire dynamics and elevating the threat they pose.

Fire’s Perfect Storm

Wildfires depend on three essential components to proliferate: favorable weather, dry fuel, and an ignition source. Each of these elements has experienced significant transformations in recent decades. While climate change establishes the conditions for larger and more intense fires, human activities are actively intensifying the flames.

Climate and Weather

Extreme heat plays a perilous role in wildfires. High temperatures desiccate vegetation, increasing its flammability. Under such circumstances, wildfires light more readily, spread quicker, and burn with enhanced intensity. In the western U.S., dryness attributed to climate change has doubled the area of forestland that has burned since 1984.

Adding to the issue is the swift increase in nighttime temperatures, which are now rising more rapidly than daytime temperatures. Nights, once providing relief with cooler conditions and higher humidity, are less frequent in doing so, enabling fires to continue raging uninterrupted.

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Ultimately, winds play a significant role in the swift growth, heightened intensity, and unpredictable dynamics of wildfires. Wind bursts propel heat and embers forward of the flames and can lead to rapid expansion. They may also trigger spot fires in new areas. Furthermore, winds boost combustion by providing additional oxygen, making the fire more volatile and difficult to manage. Typically driven by strong winds, fast-spreading fires have become more prevalent in recent years.

Fuel

Fire is an inherent process that has influenced ecosystems for over 420 million years. Native populations historically utilized controlled burning to manage terrains and diminish fuel accumulations. Nevertheless, a century of fire suppression has permitted extensive regions to amass dense fuels, setting the stage for larger and more ferocious wildfires.

Invasive species, like certain grasses, have intensified the problem by creating uninterrupted fuel beds that hasten fire propagation, often doubling or tripling fire activity.

Moreover, human advancement in fire-prone areas, particularly in the wildland-urban interface, where communities blend with forest and grassland flora, has introduced new, highly combustible fuels. Structures, vehicles, and infrastructure tend to ignite easily and burn hotter and quicker than natural vegetation. These alterations have significantly modified fuel patterns, establishing conditions favorable for more severe and challenging wildfires.

Ignition

Lightning can ignite wildfires, but humans account for a growing proportion. From unattended campfires to arson or sparks from power lines, over 84% of the wildfires affecting communities are initiated by humans.

Human actions have not only tripled the duration of the fire season, but they have also caused fires that present a greater risk to individuals.

Fires started by lightning usually coincide with storms that bring rain or increased humidity, which slows the fire’s spread. In contrast, fires ignited by humans typically ignite under more extreme conditions—higher temperatures, lower humidity, and stronger winds. This results in greater flame heights, quicker spread in the vital initial days before teams can react, and more severe ecological consequences, such as killing a greater number of trees and degrading the soil.

Human-induced fires frequently take place in or near populated areas, where combustible structures and vegetation create even more perilous conditions. Homes and surrounding materials, such as wooden fencing and porches, can ignite rapidly and send burning embers aloft, further spreading the flames.

As urban expansion encroaches into wildlands, the likelihood of human-caused fires and the properties potentially exposed to fire increase, leading to a feedback loop of rising wildfire risk.

Whiplash weather

A phenomenon referred to as whiplash weather, characterized by abnormally wet winters and springs followed by severe summer heat, has been particularly conspicuous in Southern California in recent years.

A damp spring in 2024 encouraged vegetation growth, which subsequently dried out under intense summer heat, turning into highly flammable fuel. This progression contributed to some of the most significant fires of the 2024 season, several of which were human-caused.

That aridity persisted in Southern California through the autumn and into early winter, with minimal rainfall. Soil moisture in the Los Angeles area was around 2% of historical levels for that time of year when fires ignited on Jan. 7, 2025.

As the elements that can trigger wildfires converge, the potential for increasingly severe fires looms ever larger. Severe fires also release significant amounts of carbon from trees, plants, and soils into the atmosphere, heightening greenhouse gas emissions and worsening climate change, contributing to more extreme fire seasons.

This article was initially published on The Conversation. Read the original article.