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How Do Wildfires Start?

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Natural Causes of Wildfires

How Do Humans Cause Wildfires?



Wildfires are a huge environmental, societal and economic problem that is set to get worse. Every year, tens of thousands of wildfires burn across the globe, devastating vast areas of land as well as habitats and infrastructure, causing untold misery to surrounding communities.

Previous blogs have looked at recent wildfire trends and have delved into what exactly makes something a wildfire. This article will look more closely at how wildfires start: what causes them in the first place?

For the purposes of this article, we will focus on unplanned, out-of-control wildfires, rather than controlled fires that serve an important ecological function.

Research shows that in the United States, up to 84 percent of wildfires are caused by people. Since human-caused wildfires spread faster, burn hotter and destroy more trees than ones caused by natural phenomena, efforts to prevent them should be of paramount importance.

This damage is wide ranging: billions of tonnes of CO2 being emitted, billions of animals perishing and hundreds of billions of financial losses being incurred. And this is before we even start taking into account the respiratory issues and health complications that wildfires cause.

Natural Causes of Wildfires

Though overwhelmingly caused by humans, wildland fires can be naturally occurring. These causes can vary depending on a particular region’s climate, vegetation and topography. Natural causes of wildfires include lightning strikes, volcanic eruptions and fires being ignited by the sun’s heat.


The most common cause among naturally occurring wildfires is lightning strikes. Lightning can hit power cables, trees, or dry vegetation and cause forest fires to ignite.

According to the BBC, more than 12,000 dry-lightning strikes started over 650 wildfires across California in August 2020, burning more than 1.5 million acres of land, with hundreds of thousands of people evacuated.

Volcanic eruptions

Volcanic eruptions are another natural cause of wildfires. Hot magma from the earth’s crust is expelled as lava during a volcanic eruption, causing it to flow down mountainsides and spread out over the forest floor, starting fires.

Because the lava from a volcanic eruption has such a high temperature, it burns everything in its path and the fuel does not need to be very flammable.

How Do Humans Cause Wildfires?

As mentioned, people are to blame for the vast majority of wildfire instances around the world. What’s worse is that research suggests that human ignition is to blame for a staggering 97% of wildfires that threaten homes in the US. Quoted in, Stijn Hantson, a fire ecologist at the University of California, said that human-caused wildfires spread twice as fast as naturally-caused ones, burn more intensely, and kill “double or triple” the amount of trees.

human caused wildfires statistic graphic

So when it comes to people, what causes wildfires?

Human carelessness is often the primary culprit. Arson, campfires, discarding lit cigarettes, playing with matches or fireworks: there are many ways humans can cause wildfires, either intentionally or through negligence.


A grim and sobering fact about wildfires is that many are started intentionally as acts of arson. Arsonists’ motives can be hard to discern, but are said to include real estate speculation, building land reclamation, and pasture management.

According to a report by the National Fire Protection Association, there were 52,260 intentional fires started between 2014 and 2018 in the US. These resulted in an estimated 400 civilian deaths, 950 civilian injuries, and $815 million in direct property damage each year.


Campfires that are left unattended or that aren’t properly and completely extinguished are a common cause of wildfires.

Left unattended, campfires can quickly get out of hand. They can then turn into wildfires themselves or emit burning embers and ash that spark fires nearby.

Campfires are often enforced by local authorities, who insist that they should only be held in rock-ringed fire pits and not until there are shovels and a plentiful supply of water nearby. However, these rules are often not adhered to and many campfires are started outside of designated campsites and areas, making them harder to control and manage.

Just as important as controlling the fires themselves is ensuring that they are properly put out. Simmering and sizzling embers can stay hot for hours (sometimes days) after a fire has ostensibly been extinguished. These can then be blown elsewhere by strong winds and are often still a hot enough heat source to start new fires. If this happens in hot, dry climates where there's a lot of vegetation, a blazing wildfire can start in no time.

One of the devastating forest fires caused by unattended campfires was the Ham Lake fire in 2007. As well as hundreds of properties, this fire burned down 75,000 acres of forest along the Gunflint Trail in northeast Minnesota.

Burning Debris

Burning debris in a forest

In a similar fashion, carelessness when it comes to debris burning can easily lead to catastrophic wildfires. With the right weather conditions, people burning yard debris in their yards could easily spell a wildfire in the works. For example, wind can cause the flames rising from a pile of burning yard waste to unwanted areas, starting new fires.

Insufficiently extinguished fires again pose a significant wildfire risk. Fires can look like they’re completely burnt out, only for a smoldering ember to catch in the wind and start a whole new fire elsewhere.

Equipment, Machinery and Infrastructure

Research shows that broken or faulty power lines are the third most common cause of wildfires and are responsible for 10% of wildfires (approximately 400 fires) per year in California.

We already know that, in the right circumstances, all that’s needed to start a wildfire is a spark.

Equipment malfunctions and sparks from engines are a significant cause of wildfires around the world. For example, farm equipment or machinery used by construction companies are often to blame. While many such machines are now equipped with spark arrestors, these devices aren’t able to completely eradicate sparks, meaning they can still be blown astray and be capable of starting new fires.

For example, Zaca Fire (2007), the fifth biggest California wildfire on record, was caused by sparks from a metal grinder. The Carr Fire (2018) was ignited by sparks from a trailer's broken wheel rim and is the seventh-most destructive fire in California's history.

Zaca Fire and Carr Fire statistics graphic

Discarded Cigarettes

Lit cigarettes are often discarded from buildings and cars and these can ignite the dry vegetation on which they land, starting fires that can quickly spread.

In 2017 in the US alone, wildfires caused by discarded cigarettes were responsible for $6 billion in property damage.


Wildfires are a pressing social, environmental and economic problem that’s getting worse. Responsible for 20% of global CO2 emissions, wildfires emit more greenhouse gasses into the atmosphere than all forms of transport combined. The good news is that in the fight against climate change, tackling wildfires can be considered to be relatively low-hanging fruit.

Public education and awareness campaigns doubtless have a key role to play in aiding people’s understanding of the causes and dangers of wildfires. This article has highlighted the primary causes of wildfires around the world, both natural and human-caused.

Unfortunately, accidents and mistakes are still going to happen, arson will continue to take place, and naturally occurring wildfires will carry on being an issue. The fight against wildfires is therefore going to take more than public awareness campaigns.

Thankfully, technological solutions are coming to the fore. It goes without saying that the sooner the authorities can get to a fire, the easier to extinguish it will be. This is why early detection is so crucial in stopping fires from getting out of hand. And how fast do wildfires spread? Our previous blog showed that they can reach speeds of up to fourteen miles-per-hour, making their early detection ever more critical.

Ocular-based systems such as cameras, satellites and drones can be effective at tracking wildfires once they’ve started, but for early detection, they are often too late in raising the alarm. By the time they’ve seen a fire, it can be hours if not days since its ignition, more often than not resulting in a large-scale and very destructive wildfire scenario.

wildfire detection speed differences graphic

Increasingly, it looks as if sensor-based systems are the way forward. Dryad’s Silvanet technology is the fastest and most accurate solution when it comes to wildfire detection. Our new ultra-early detection technology detects wildfires at the smoldering stage and provides precise geographical data so that firefighters can locate and extinguish them quickly and safely.

Ultra-early wildfire detection technology has the potential to protect $30 billion in economic losses, stop 3.9 million hectares of land from burning, save 237 million animals and prevent 10,000 respiratory cases by 2030.

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