The causes of wildfires can be broadly categorized into natural causes and human-related causes.
Natural Causes of Wildfires
- Lightning strikes are the most common natural cause, especially "hot lightning" which generates intense heat sufficient to ignite dry vegetation.
- Volcanic eruptions can start fires with hot lava flowing down and burning surrounding forests.
- Spontaneous combustion of decomposing organic materials like dry leaves can also ignite fires under certain conditions.
- In some instances, sparks from rock falls can ignite fires naturally.
Human-Related Causes of Wildfires
- Human activities are responsible for the vast majority of wildfires worldwide—accounting for about 84-97% of wildfire incidences threatening homes in the US.
- Common negligent actions include unattended campfires, discarded cigarette butts, debris burning, equipment sparks (from machinery or power lines), and fireworks.
- Arson, the deliberate setting of fires, is a significant cause in some regions.
- Faulty power lines and equipment malfunctions also frequently spark wildfires.
- Improperly managed prescribed burns or yard debris fires can escape control and ignite wildfires.
Climate Change and Environmental Factors
- Climate change exacerbates wildfire conditions by causing hotter, drier weather and longer droughts, drying out forests and vegetation, which then serve as fuel for fires.
- Warmer temperatures facilitate more frequent and severe lightning strikes, increasing natural ignition events.
- Changes like earlier snowmelt reduce water available for plants, making forests more flammable.
- Overall, climate change increases the frequency, size, intensity, and duration of wildfires globally.
In summary, wildfires start from a combination of dry vegetation, heat, and an ignition source, mostly triggered by human activities but also naturally by lightning, volcanic activity, and spontaneous combustion. Climate change is a major factor worsening wildfire risks and severity.
