Wildfires are often described as natural disasters, evoking images of an unstoppable force of nature. However, the question of whether a wildfire is purely a natural phenomenon or largely a human-influenced event is complex. While fire has always been a part of many ecosystems, human activities increasingly shape the frequency, intensity, and impact of these destructive events. Understanding this distinction involves examining the fundamental definitions of disasters and the varied origins and behaviors of wildfires.
Defining Natural Disasters
A natural disaster is typically understood as a calamitous occurrence primarily generated by natural processes. These events often occur on a large scale and result in widespread damage, loss of life, or significant economic impact. Such events are considered beyond immediate human control in their fundamental origin, distinguishing them from human-made disasters like oil spills or chemical contaminations.
Wildfire Origins: Natural and Human-Caused
Wildfires can originate from both natural and human sources. Naturally occurring wildfires are most frequently ignited by lightning strikes. Lightning-caused fires account for a smaller percentage of overall ignitions, typically 12-16%, but are responsible for a disproportionately large area burned, sometimes up to 60-70%.
Conversely, human activities are the predominant cause of wildfires. Nearly 85-90% of wildland fires in the United States are human-caused. Common human ignition sources include unattended campfires, discarded cigarettes, equipment malfunctions, power lines, and debris burning. Arson also accounts for a significant portion of human-caused wildfires.
Human Influence on Wildfire Behavior
Human actions extend beyond ignition, influencing wildfire behavior, severity, and spread. Decades of fire suppression policies, aimed at extinguishing all fires, have led to an unnatural buildup of combustible vegetation, known as fuel, in many forests. This accumulation means that when fires do ignite, they burn hotter and more intensely, leading to greater destruction.
Climate change further exacerbates wildfire conditions. Rising global temperatures, prolonged droughts, and altered precipitation patterns create hotter, drier landscapes. These conditions dry out vegetation, making it more flammable and extending fire seasons. Studies indicate that climate change has enhanced the drying of organic matter and increased the number of large fires in the western United States.
Development in the wildland-urban interface (WUI), where human settlements meet undeveloped wildland, also plays a substantial role. Building homes closer to wild areas increases the risk of ignitions and places more lives and property in direct harm’s way. Close to one-third of the U.S. population is now at risk from wildfires in the WUI.
The Interplay of Nature and Human Impact
Modern wildfires represent a complex interplay between natural processes and human influences. While natural events like lightning can ignite fires, human factors often determine how devastating those fires become. The conditions that allow fires to grow into large-scale disasters are shaped by human actions.
Many contemporary wildfires defy simple categorization as purely “natural” disasters. The amplified role of human activities in creating fuel loads and conducive fire weather means that even naturally ignited fires can become “unnatural” in their intensity and impact. Despite a global decline in total burned area over recent decades, human exposure to wildfires has increased, driven by population growth into fire-prone landscapes and increased fire intensity in populated areas. This highlights that the distinction is less about the initial spark and more about the conditions that allow the fire to become devastating.