The anatomy of wildfires is an interaction between the devastating flames and the subsequent renewal.
Every summer, a region or area of the globe is subject to violent destructive forces in the form of natural fires. We look horrified at the high flames and feel with the people who, at worst, are killed in the disaster or who are loosing great values - both financially and their life story. Rarely, the scale and disaster are as extensive as it has been seen in Sweden and Greece, but fire is a devastating force.
It is therefore natural that, in mythological terms, fire has played an important role. Most pronounced probably in the universal rebirth after Ragnarok, where the world is going under in a vast sea of flames. On the smaller scale, dwarves are sitting in the volcano’s interior and forging weapons with strong forces or creating jewelry with supernatural powers, as we know it from the Lord of the Rings, where magic powers can only be lifted by the volcanic fire. In the Christian religion, we find the fire in the purgatory, where man undergoes a cleansing process for all his sins and then to be saved.
The world over fire can be found in the mythology, and it is through the fire faith combines both destruction and renewal.
In the Greek philosophy, as it was formulated by Aristotle – and before him Empedokles – the fire was one of the four elements, where the three others were air, water and soil with each season. The fire belonged to the summer, what might just say that at that time it was the season of natural fires. In that sense, there is nothing new in the actual events, but the consequences seem immediately greater in our time, even though the people of Greece now lost their lives and values in the days of fires.
Natural fire physics
It is quite simple to put an end to the conditions that can create natural fires. These sometimes occur naturally, and in other cases, probably the most, they occur by human influence. But common to all of them is that nature must first go through a drying period where the water in the soil and plants evaporates and leaves dry flammable material. Of course, the weather is an important player here, because drying is done when water evaporates without water from other sources replace it – especially as we see it in rainfall.
It is possible to some extent counteract dehydration by irrigation, but it is both expensive and cumbersome. In areas with rivers or smaller streams, the water from here can be led over the fields, but only to the extent that the river can be maintained with water supply from remote sources.
Overlooking the globe, there are built-in areas in the climate system where drought naturally occurs. It is especially the subtropical high-pressure areas, located in two belts around 30-40 degrees north and south. These areas arise because of the general atmospheric circulation, which generally divides the earth into six zones – three in each hemisphere. Each hemisphere has a tradewind from Equator to 30 degrees N / S, the westerlies between 30 and 60 degrees N / S and an area of polar east wind from 60 to 90 degrees N / S.
The above-mentioned subtropical high-pressure areas are formed between the tradewinds and the westerlies. But there is also a seasonal variation, so that the subtropical high pressure in the summer period is drawn towards the poles, so that in the northern hemisphere during the summer period they will stay around the Mediterranean region.
In high-pressure areas there is a general air subsidence in the atmosphere. This movement will make the air drier and prevent the formation of large cloud formations. That’s why the Mediterranean region in summer is the destination of many holidays as it is almost certain you will see sunny and warm weather.
Anatomy of forest fire
Just the warm and sunny weather has a backside, which is rarely registered, as holidays most often is made in the coastal areas. Inland, the sun together with the high temperatures and the lack of precipitation will create the foundation for natural fires. If ignition does not occur, plants and trees will simply wipe out without any consequences other than that of reducing growth. As this is a recurring situation every year around the Mediterranean, the normal plant growth in the area is used to it as part of the plant’s life cycle.
But occasionally there will be an ignition. This can occur naturally by a lightning strike if conditions for thunderstorms occur. It requires heat, humidity and special temperature conditions through the atmosphere, but it is not uncommon for such situations to occur. Lightning into dry woodlands can then ignite the trees, and the natural fires are a reality. The rain that is also part of the thunderstorm will not necessarily turn off the ignited wood. The rain falls in a very small area, which is not necessarily where the lightning struck down, and on the other hand, thunderstorms can be formed high in the atmosphere, so the rain will evaporate before it reaches the ground.
Human interference is more diverse and, in the vast majority of cases, is caused by carelessness and irregularity. Direct ignition can be done with cigarette or from bonfire and grill that is not extinguished completely. More surprisingly, glass pieces from bottles may seem like a burning glass when the sun shines, thus igniting dry grass.
Regardless of how the ignition occurs, local conditions will subsequently determine whether the fire can spread. It will be a question of how much flammable material is available, and the weather will be a crucial factor. Quiet weather will make extinguishing easier, but the fire and the heat that emerges will be able to create its own local wind system. The heat the fire produces will heat the air, which then rises into the atmosphere. This will cause air from the side to be pulled into the flames to compensate for the ascending air. It creates heavy gusty winds that can cause the flames to jump many meters. These gusts are completely unpredictable and therefore one of the greatest risks in these natural fires.
Wind is also an important factor in the common forest fires in California. When they appear in the late dry autumn, there is a risk that cold – and thus heavy – dry air from high altitude plateaus in Rocky Moutains thrives down through the valleys to Los Angeles. This wind, called Santa Ana, can be extremely strong and can come with hurricane strength. An ongoing forest fire in the areas of eucalyptus trees will flare up and be very difficult to get under control.
Because the subtropical areas are exposed to this desiccation each year, both population and nature have learned to live with that risk and their preparedness is usually high. In rare occations fires become so extensive that it become disasters. In recent years, however, we have seen examples in both Portugal, Spain, France and indeed this week in Greece near Athens, where fires suddenly evolved near inhabited areas.
Many times the authorities consider if a natural fire should be allowed to burn out of its own. This can happen if the ignited area does not pose a greater risk of spreading. But there are also attitudes that say that the fires that occur can contribute to a rejuvenation of nature. It is well-known that a burned area where trees and bushes have for years prevented sunlight from reaching the surface of the earth, the following year is flowering in a completely new way because seeds have been stored in the crust and just waiting for light and heat.
Disaster in Yellowstone
The very idea that natural fires are part of nature’s cycle has been part of nature care in many places – in Yellowstone National Park in Wyoming, USA. Here in 1972, it was decided that fire caused by nature’s own forces in the Yellowstone National Park should be allowed to burn or be extinguished by a natural rainfall. Fire caused by human carelessness or even pyromania should extinguished.
When a fire occurred on June 22, 1988 because of a lightning strike, it was allowed to burn, but the weather conditions were unfavorable, because there was no rain and the wind increased. It burned until mid-October and over 3200 km2 of forest went into ashes. After that incident, 1992 adopted more specific rules for when a fire may be allowed to burn itself.
Controlled wildfires
Before Europeans invaded North America, Indians used controlled natural fires for different purposes. Fire was used to clean areas for agriculture, but also burning of the prairie’s large pastures should prevent bushes and trees from gaining a foothold. This gave the grass the best conditions for the benefit of the big animal flocks that were the hunting of the Indians. In the hunt, the Indians could also use fire to push the prey to areas where they were easier to hit.
To what extent these alleged fires came out of control for the Indians, there is no data for, but the idea of using fire-making nature care is maintained to today. An important prerequisite for controlling a natural fire is to reduce the amount of combustible material. Therefore, dead trees are removed in areas where a burning must take place.
In Denmark burning of fields after the harvest until 1990 was a common means of removing excess harsh, which was impossible to assemble. It was cheaper to burn it than to plow it down, even though the fertilizer effect was greater. However, straw fires and the use of straw in the heating plants meant that after 1990 there could be a better use of the surplus, so burning the fields was forbidden.
In view of the debate on climate change and the greater focus on CO2 emissions, it is also not advisable to burn organic matter into the free nature. The emission of CO2 will increase that personman-made greenhouse effect and thus increase the amount of energy retained in the Earth atmospheric system.
