California Fires: The Anatomy of a Fiery Catastrophe
Forest fires are considered a natural phenomenon in the ecosystem. These phenomena are commonly observed in boreal and dry tropical forests. In moist or tropical rainforests, forest fires are a rare occurrence if not entirely absent. In the US alone, close to 4.3 million acres of land are grazed down by forest wildfires, majority of them occurring in the scorching bone-dry land of the western seaboard, particularly the states of California, Oregon, Idaho, and Montana. Elsewhere, forest wildfires have also changed some of the environmental landscape of Indonesia, France, and Portugal.
The California wildfires, known for their tenacity against control efforts, have been a perennial problem this side of the country. In August 1987, 2,600 km2 of land was scorched dry in a two-month long wildfire that spanned Oregon and California. The fire was also sparked by lightning. In 2002, almost 2,000 km2 of land was also grazed by wildfires, again sparked by lightning. In 2007, almost a million people were displaced in a wildfire that spread through 2,400 km2 of Southern California. In June of 2008, 15 lives and more than 500 structures were lost in a Northern California wildfire that set ablaze almost 5,000 square kilometers of land. Severe electrical storms ignited the almost 2,100 wildfires that spread across bone-dry part of the state. Lives were shattered, dreams were doused cold despite the hellfire, and nightmares surfaced in the middle of the day.
But what makes California a magnet for forest wildfires? Before we can understand the answer to this question, let us first try to understand how a simple wood fire is formed. That way, we can better understand the nature and behaviour of forest wildfires and perhaps, institute some measures that will somehow help prevent the occurrence of such natural catastrophes and or reduce the damage brought about by the forest wildfire.
For starters, fire occurs because of a chemical reaction between oxygen in the air around us and some other chemical or molecule that serves as the fuel or energy source. Application of heat will hasten the speed of chemical combustion reaction thus, creating fire. In forest fires, wood is the most common material that serves the fuel in the production of fire. Wood is primarily composed of carbon and may contain polysaccharides, cellulose, lignin, natural resins, and some liquid resins.
In the development of fire in wood, an agent heats the wood to very high temperatures, well within what is known as its ignition temperature. The agent can be in the form of a match, a focused light, friction, lightning, or another object or material that is already burning. By the time the wood reaches around 150o Celsius (or 300o Fahrenheit), the heat already begins decomposing some of the cellulose in the wood. This releases unstable and explosive gases into the air. These gases are visible and known to us as smoke, composed primarily of oxygen, hydrogen, and carbon molecules.
Materials that are left after the volatile gases are released make up the char, which is almost pure carbon. The wood material which is unburned or not turned into gas is called the ash. These include minerals such as calcium, potassium, chlorine, magnesium, and others. As such, charcoal fire can burn sans the smoke.
Once the volatile gases reach about 260o Celsius, or 500o Fahrenheit, the component gaseous molecules break apart into their component elements. Each element or atom then recombines with the oxygen in the air to form water, carbon dioxide, and other molecular products. This chemical reaction results to what we know as burn. The carbon molecules in the char also combine with oxygen in the atmosphere although at a much slower rate. If there is one thing worth noting in the chemical reaction of fires, that would be the generation of new heat which sustains the fire. Compared to gasoline as fuel, there are no other materials which can be left in the burning process such that no char is formed. When all the volatile gases are used up, the flames also die down as there is no more fuel to feed the chemical reaction. Wood fire is entirely different because the char serves as the long-staying fuel source for the fire. Thus, the fire in wood-driven reactions stays much longer than that initiated by other fuels like gasoline.
Now we have to understand that fire behaves in different ways depending on some factors in the three elements we know so far. Since fire is the product of a chemical reaction between oxygen and a heat-produced volatile fuel gas, the chemical component of the fuel becomes a primary consideration. Carbon and hydrogen molecules are relatively flammable, especially when combined with oxygen. Other molecules are not as combustible as these molecules such that they may not actually produce fire. The chemical bonds between molecules should also be considered. It takes a variety of time and temperatures to break the chemical bonds of molecules. This means that substances will have varying temperatures at which they reach their burning point. Some will burn at lower temperatures than others while some will need extremely high temperatures, and heat, to produce the chemical reaction seen in fires.
Applied to forest fires, anything that can heat up the dry forest environment can almost always spark or ignite a forest wildfire. In California’s experience, majority of the forest wildfires were ignited by lightning strikes during heavy electrical storms. Lightning bolts can have temperatures as high as 2,750o Celsius or 5,000o Fahrenheit and this is more than enough to break the chemical bonds of molecules that comprise wood and other materials in the forest. The reaction releases the unstable gases, reacts with oxygen in the atmosphere, producing fire. The fire initially started at one point generates more heat and this further break down the chemical bonds of molecules of surrounding materials. This fuels the fire some more until it grows out of control and you now have a wildfire.
Forest wildfires can be either ground fire or crown fire. Ground fire is wildfire that remains on the ground surface and is fuelled by combustible surface materials such as dried leaf litter, dry moss and lichen, dead grass, decaying humus, rotting or dead wood, and live brush and shrubs. Crown fire is wildfire that includes the upper parts of trees – the crown – fuelled by combustible upper tree parts such as foliage, dead branches and small twigs. Crown fires always have a ground fire spreading as a unit. There is a wildfire phenomenon known as jumping or spotting wildfire. In this phenomenon, burning twigs and or other materials from a fire are carried by the wind into other non-burning areas of the forest to start a new fire. This means that fires can be set off in other places through the transfer of flaming materials into a dry and highly combustible area.
How fast a forest wildfire can spread depends on the moisture content of the combustible materials brought about by inclement weather conditions and other weather phenomena. In places with dry combustible materials, wildfire can spread to as fast as six kilometres per hour. Where the area has moist combustible materials, the spread of wildfire can be as slow as half a kilometer per hour.
The management of forest wildfires should then be anchored on the understanding of this behaviour of forest fires. Since the major elements of fire are fuel, oxygen, and heat, making some changes in any of the three will result in a change in the behaviour of fire. In order to minimize wildfire, authorities have employed methods to reduce the number of available fuel or potential fuel sources for a fire. An example of this is through controlled burns where an area is purposely set on fire. Authorities have also altered the fuel sources through the shredding of trees and vegetation to a mulch which serves as a protective covering for the forest floor, retaining moisture in the process. Some communities have employed large firefighting divisions ready to respond at a call. Helicopters and other technology are employed to speed up firefighting capabilities as well as to assure the safety of the people.
However, the perennial California forest wildfire phenomena is more than just the wrath of nature pitted against human resolve for existence and protection of his interests. If any, the California fires are a grim reminder of our place in this life. Forest wildfires exist because they are normal part and occurrences of the forest, as natural as trees belonging to the forest themselves. No amount of fire suppression nor firefighting know-how and technology can ever stop a forest fire from becoming. Nature is something man cannot control, not now and not ever. Forest wildfires start for a reason and whatever reason we may have in trying to control the wildfire may as well end up in futility because once a forest fire starts, it will burn more fiercely and more relentlessly the more we try to control it.
Ironically it may seem but we have set the wheels of more catastrophic forest wildfires rolling by tampering with the natural cycle of forest wildfires. We should understand that nature has meant for the boreal forest to provide fire-wrecked stands of same-age trees to create a natural firebreak or firewall. By altering this natural process by fire suppression in these same tree stands, we have ignited the fire that fuels a larger, wide-ranging and more catastrophic forest wildfires.
