My inquiry question is “How should government funding be used for the prevention of wildfires?”. For my first round of research, I want to have more background information and a good understanding of wildfires. I will be learning about what wildfires are exactly – how they work and the different types – as well as the different causes of wildfires and factors that may make the fire even more destructive.
- Wildfires are uncontrolled blazing fires occurring in the wilderness that can very quickly spread and consume vast areas of land (1, 2, 3, 4, 5).
- Every year, approximately 100,000 wildfires occur in the United States alone, and have burned around 9 million acres of land in the U.S. in recent years (1, 3).
- Wildfires are also referred to wildland fires (1, 3, 6), forest fires (1, 3, 4, 5, 6), vegetation fires (3, 4), grass fires (3, 4, 5, 6), peat fires (3, 4, 5, 6) and bush fires (3, 4, 5, 6). It depends on the type of vegetation that is burnt (4, 5, 6).
The conditions for a wildfire to occur
- Simply put, a fire is the part of a combustion you can see, a combustion being a chemical reaction of three things: heat, fuel and oxygen (5). Heat, fuel and oxygen are the three key ingredients to a wildfire, and these conditions must be present in order for a wildfire to start and continue to burn (1, 5, 6, 7, 8, 9).
- Fuel: Fuel can be any flammable material (1, 5, 7), whether it be gas, solid or liquid (5). Common fuels for wildfires are trees, dry leaves, brush, grass and houses (1, 5, 6, 7). Fuels containing less moisture usually burn faster than fuels with more moisture (5).
- Oxygen: As you already know, oxygen is a gas found in our air (5, 8). The air that we breathe contains approximately 21% of oxygen, yet only 16% is required to start a fire. The burning fuel reacts with the oxygen in the surrounding air, and this chemical reaction produces heat and other products including gases, particles and smoke. This process is called oxidation. The reason why smoke can be quite dangerous is because the gases produced by this process can be very deadly, depending on what is being burned (5).
- Heat: All material has its own flash point, which is the temperature at which the material will burst into flames. The flash point for wood is 572 degrees Fahrenheit (300 degrees Celsius) (9). Once it is heated enough, hydrocarbon gases are released and mix with the oxygen in the air, causing it to combust and create a burst of flame (6, 9). The surrounding fuels of this flame are then preheated and in turn, other fuels are heated up. That is how a fire can spread (6).
- Firefighters often refer to the relationship between these three components as “The Fire Triangle” (5, 9).
- Without one of these three ingredients, the fire triangle will not stand. If there isn’t enough heat, or if the fuel or oxygen runs out, the fire will not burn (5).
Causes of wildfires
Natural causes: 10% of wildfire causes are natural (4)
- Lightning (1, 2, 3, 4, 5, 6, 7, 8, 9): Lightning strikes are able to produce a spark that can set a fire (3, 4, 5, 8), especially the type of lightning called “hot lightning”, which strikes repeatedly for longer periods of time (3, 4).
- Volcanoes (2, 3, 4): The hot burning lava that is expelled during a volcanic eruption can flow onto fields or land close by and start a wildfire (3, 4).
- Sun (1, 7): Sometimes, all the heat a wildfire needs to start is a hot burning sun (7).
Human causes: 90% of wildfires are man-made (1, 3, 4)
- Unattended campfires (1, 2, 3, 4, 5, 7, 9): Many people enjoy having campfires when they are camping, but if a fire is left unattended or not put out properly, it may ignite a wildfire (3, 4, 5).
- Cigarettes (1, 2, 3, 4, 5, 7, 8, 9): People may be smoking while they’re driving, walking or biking and then discarding the cigarette butt without completely putting it out, which can start a fire (3, 4, 5).
- Fireworks (3, 4, 5, 9): If fireworks are not handled properly and there are any sparks that land where they weren’t supposed to, the sparks can start a huge wildfire (3, 4, 5).
- Burning debris (3, 4, 5, 6, 9): Burning yard waste and garbage is a fairly common thing to do to get rid of accumulated waste, but these flames may spread and cause a wildfire (3, 4, 5).
- Engine sparks (3, 4, 5): When things go wrong, sparks can be spewed by an engine (3, 4, 5). Some common machinery accidents that cause wildfires are from lawn mowers, gas balloons, and car crashes (4, 5).
- Arson (2, 3, 4, 5, 6, 7, 9): There are some people called arsonists who will intentionally set fire to vehicles, houses, property, or anything to purposely cause damage (3, 4, 5).
Factors of wildfire intensity
-Fuel load (5, 9): the speed and intensity at which a fire spreads depends on the fuel composition (5, 9). Small fuel loads will burn slower and less intensely, whereas if the fuel load is very large, the fire will be more intense, making it burn more quickly (9). The moisture content/dryness of the fuel also plays a role in the intensity of the fire and how quickly it spreads. Dry fuel will burn much faster than fuel with high moisture content (5, 9). The time it takes for a fuel material to ignite varies. The principle variable for the time it takes to ignite is the ratio of the fuel’s total surface area to its volume. For example, the surface area of a twig isn’t much bigger compared to its volume, so it ignites quickly. On the other hand, a tree’s surface area is much small compared to its volume, so it takes longer to ignite (9).
-Weather: winds will supply the fire with even more oxygen and direct it towards more potential fuel. Hotter temperatures will absorb moisture from the fuels which allows them to ignite more easily (5,9).
-Slope: wildfires typically travel faster uphill than downhill, and the more steep the hill, the faster it will burn. This is due to steep hills tending to have lots of fuels close together and the wind is much more aggressive going uphill (5).
How wildfires spread – types
-Surface fires: surface fires burn at the surface of the ground, burning quickly (5, 6) but at a low intensity (6).
-Crown fires: crown fires burn very intensely, occurring higher up in the trees (5, 6).
-Ground fires: ground fires burn the vegetation and organic material in the soil (5, 6).
-Spotting: fires can also generate their own wind and throw embers into the air and spread the fire elsewhere. This is called spotting (5, 9)
That’s it for this week! In my next round of research, I will be looking at the impact of wildfires on vegetation and wildlife. Any comments, ideas or websites are welcome. Thanks for reading!