FOREST FIRES: CHARACTERISTICS, CAUSES, CONSEQUENCES, TYPES - ENVIRONMENT - 2025

The forest fires are uncontrolled fires consuming large areas of forests and other vegetation types. They are characterized by being fires whose combustible material is wood and plant tissues and the wind intervenes in their development.

These fires can be caused by both natural and anthropogenic causes (human actions). In the first case, they occur due to lightning effects in extreme drought conditions with high temperatures, but most are caused by accidental or intentional human action.

Forest fires. Source: Cameron Strandberg from Rocky Mountain House, Alberta, Canada / CC BY (https://creativecommons.org/licenses/by/2.0)

They are one of the main causes of degradation or loss of ecosystems, since they can completely eliminate the vegetation cover, as well as the fauna of the area. This increases soil erosion, increases runoff and decreases infiltration, thereby reducing water sources.

There are three basic types of forest fires determined by the type of vegetation, humidity, temperature and wind regime. These are surface fires, canopy fires, and underground fires.

To prevent forest fires, public awareness of the problem and its consequences is essential. In the same way, the environmental nursery, detection and early warning systems, as well as having teams of forest firefighters.

Characteristics of forest fires

Forest fires are characterized by occurring in open areas where the wind plays a determining role. On the other hand, the flammable material that feeds them is vegetable matter, such as lignin and cellulose that burn easily.

For them to originate, the combination of a combustible material, heat and oxygen is necessary. The main influencing factors are the presence of dry vegetation and low soil and air humidity, as well as high temperatures and wind.

Specific composition

The plant species at a given site can determine the magnitude and speed of fire spread. For example, conifers such as pines and cypresses produce resins that increase the combustibility of plant material.

Also, some angiosperms from families such as Anacardiaceae and dry grasses (grasses) are excellent fuel. In high grasslands in particular, flames spread with great speed.

Topography

The relief of the terrain where the forest fire develops and the direction of the wind are determining factors in the spread and scope of the fire. For example, a fire on mountain slopes with rising drafts spreads at high speed and with flames from great height.

Also, when there is a steep slope, fragments of burning combustible material (firecrackers) easily drift downward.

Fire and ecosystems

Amazon fires in August 2019. European Space Agency

There are ecosystems where fire is one of their functional characteristics and species have adapted to periodic fires and are even dependent on fire. For example, in Mediterranean savannas and forests there are periodic burns that renew vegetation and promote the germination or regrowth of some species.

On the other hand, many other ecosystems do not tolerate fire, and are severely affected by forest fires. This is the case of tropical humid forests, deciduous tropical forests among others.

Parts of a forest fire

The parts of the forest fire are fundamentally determined by the direction of advance of the fire, which depends on the wind. In this sense, a fire front, flanks and a tail are defined, as well as the secondary sources.

From the starting point, the fire expands in all directions on the plane, but the dominant direction of the wind defines its characteristics.

The fire front

It is the front edge of the fire favorable to the dominant direction of the wind where the flames are high and tongues of fire can appear. The latter are longitudinal extensions of the front, which are covering the land and expanding the fire area.

Side edges

These are the lateral parts of the fire in relation to the forward front, where the winds affect laterally. In this area, the intensity of the fire is lower and its progress slower.

The tail

It is the back of the forest fire and corresponds to the place of origin of the same. At this point, the flames are lower because most of the combustible material has been consumed.

Secondary lights

It is common for fire sources to be generated far from the main core, due to the action of fragments of ignited material that move due to the action of the wind or steep slopes.

Causes

Forest fires can originate from natural causes or be caused by human actions.

- Natural causes

Some vegetation fires occur due to strictly natural causes such as lightning strikes. Likewise, the possibility of spontaneous combustion of certain types of vegetation under suitable conditions has been pointed out.

However, some researchers deny this possibility because the temperatures required to start a forest fire exceed 200 ºC.

- Human causes

More than 90% of forest fires are caused by humans, either by accident, negligence or intentionally caused.

Accidents

Many wildfires are started by short circuits or overloads in power transmission lines that pass through natural areas. In some cases this happens because weeds are not removed at the bases of the towers and the course of the power lines.

Negligence

A very common cause of wildfires is badly extinguished or uncontrolled bonfires. In the same way, the burning of garbage or cigarette butts thrown on the side of the road.

Intentional

Man-made wildfires are very common. Thus, there are those caused by people with mental problems who enjoy setting fires (pyromaniacs).

On the other hand, many forest fires are deliberately caused to destroy the vegetation cover and justify the use of the land for other purposes. For example, it has been reported that the main cause of fires in the Amazon is intentional burning to introduce pastures and crops, mainly soybeans.

Fires in the Amazon. European Space Agency

Consequences

For ecosystems where fire is part of their natural dynamics, the consequences are generally positive. However, in most cases forest fires have highly negative consequences for the ecosystem and human beings.

Biodiversity losses

Forest fires cause a direct impact by decreasing biodiversity in the ecosystem. Fire causes the death of plant and animal species, as well as other organisms such as fungus, mosses, lichens and ferns.

Loss of biodiversity. Source: Mark Wolfe / FEMA / Public domain

Only those fire-tolerant species (pyrophiles), such as some palms, trees and grasses, are not affected. On the other hand, when the habitat is degraded there is a secondary disappearance of species or many are forced to migrate in order to survive.

Loss of water sources

The disappearance or degradation of the vegetation cover and the organic matter of the soil increases the runoff of rainwater, reducing infiltration. Therefore, groundwater reserves are reduced and sediments carried from the soil that fill the reservoirs increase.

Furthermore, as the forest area decreases, its capacity to contribute to the production of rain and the capture of environmental humidity is affected.

Soil deterioration

As the soil is exposed due to the loss of vegetation, the loss through erosion increases. In addition, fire decreases the organic matter in the soil and affects its biological activity, moisture content, and mineral ion exchange capacity.

Global warming

Forest fires make an important contribution to increasing global warming. The forests that capture and retain atmospheric carbon are destroyed and the retained carbon is released in the form of CO _2, which is a greenhouse gas.

Public health problems

The smoke and particles generated by forest fires cause serious respiratory problems for nearby populations. More directly, people can suffer burns and even death from being caught in forest fires.

Damage to infrastructure and services

Forest fires produce flames that sometimes reach great heights and can affect infrastructure present in the area where they develop or in nearby areas.

Housing and other infrastructure

When forest fires reach large areas, they sometimes end up affecting nearby residential areas. Therefore, cases of forest fires that end up generating structure fires are common.

Power lines

When wildfire flames hit high-voltage power lines, they cause surges. These overloads trigger the security mechanisms of the system and the electricity supply to large urban and industrial areas is cut off.

Loss of resources from the ecosystem

Forests and other ecosystems are a source of food, medicinal, genetic and industrial resources that can be used in a sustainable way. By destroying species in the ecosystem, forest fires cause the loss of these resources.

Decrease in tourist activity

One value of ecosystems is their potential for tourism. Undoubtedly, this is negatively affected by forest fires, both because of the risk to the safety of tourists during their occurrence, and because of the environmental degradation they produce.

Economic losses

The negative impact of forest fires is also manifested economically, due to the loss of forest resources and infrastructure, the costs associated with health problems, human displacements and subsequent remediation measures.

Types of forest fires

Forest fires can be classified taking into account various criteria, including the type of plant formation where they occur. In this sense, we speak of forest fires themselves and fires of savanna or grasslands in general.

In terms of how they occur, forest fires are classified into three types: surface, canopy and underground.

Surface fires

This type of fire spreads mainly through the surface of the ground, burning the herbaceous and shrubby vegetation of the understory. It occurs mainly in ecosystems such as ungrove (treeless) savannas.

Cup fires

They occur in wooded areas where the trees have the crowns very close and the fire attacks them. Therefore, the fire advances from crown to crown regardless of the forest floor.

Underground fires

Subterranean forest fires occur mainly in areas with soils rich in organic matter. For example, in peatlands areas because fire consumes the peat below the ground.

Many times the outbreaks are not detected and are not easy to combat. Thus, peatlands can burn for weeks under these conditions.

Super forest fires or hungry fires

Hungry fires. Source: John McColgan / Public domain

They consist of forest fires that, due to their great magnitude, feed off each other by generating their own development conditions. Very extensive plant formations occur in conditions of extreme drought, so there is abundant combustible material.

Due to their extension and intensity, they generate large amounts of heat and produce firestorms. These super fires or sixth generation fires are becoming more common, due to the changing climatic conditions on the planet.

For example, during 2019, these types of forest fires consumed millions of hectares in the Amazon, North America, Siberia, Western Europe, Indonesia and Australia.

Firestorms

In some cases, the extreme heat generated in the area causes a low pressure zone into which masses of air flow. Also, the oxygen feeds the flames and the fire becomes more intense and spreads, The hot air masses rise like columns, forming a particular type of cloud (pyro cumulonimbus). When these columns collapse, they drag masses of air downward that fuel the fire and cause it to drastically change its direction.

Prevention

Preventing the occurrence of forest fires requires an integrated program of measures that ranges from promoting public awareness to early warning systems.

- Public awareness

The starting point of a forest fire prevention program is to have a citizenry aware of the problem and its consequences. Thus, political pressure can be generated on state administrations in order to invest the necessary resources.

On the other hand, a conscientious citizen contributes to vigilance and alert, while fulfilling the necessary preventive measures.

- Eradication or control of the practice of stubble burning

A very common cause of forest fires is the practice of burning stubble and crop residues before cultivating a field. This practice, in addition to affecting the ground and the atmosphere, increases the risk of fires.

- Firewall

To prevent the spread of fires, a firebreak system should be established, either through strips devoid of vegetation or live barriers. These firebreaks are arranged separating sensitive areas from possible sources of fire startings such as roads, populated areas and others.

Firewall. Source: Lucas Martínez Farra… / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

Controlled pruning and controlled burning of combustible material also contributes to preventing the occurrence of forest fires or their spread,

Living barriers

This firebreak method consists of laying out strips with evergreen vegetation of pyrophilic species. These are species that are specifically adapted to resist or tolerate fire.

- Maintenance and assistance to the forest

An adequate prevention system must include monitoring the forest and its periodic maintenance. Accumulations of dry material in sensitive areas must be eliminated and even artificial water sources provided.

- Early warning system

A fundamental element to prevent the spread of a forest fire is to detect the outbreaks in time. For this, direct surveillance systems, technological satellite detection systems and smoke detection systems are used.

For example, the National Institute of Space Research of Brazil (INPE) detects heat sources through the AQUA satellite. This satellite uses the Modis sensor with a resolution of 1 km ².

- Forest firefighters

The existence of a forest fire department with suitable and properly equipped personnel is vital to prevent the spread of a forest fire.

Forest fires in Mexico

According to the National Forestry Commission, 98% of forest fires in this country are of human origin. From 1998 to 2013, the annual average of forest fires exceeded 10 thousand events, affecting more than 2 million hectares in total.

In 2019, a total of 7,410 forest fires occurred, affecting more than 600,000 Ha. However, 95% of this area corresponds to herbaceous and shrub vegetation, only 5% involved forests.

Forest fires in Colombia

Colombia has 18.44% of its territory that is highly susceptible to the occurrence of forest fires. The Orinoquia region is the one with the highest susceptibility to forest fires with 20,000 hectares lost between 1999 and 2002.

In the period from 2002 to 2012, more than 6,000 forest fires occurred, consuming more than 900 Ha. In 2019, more than 500 forest fires occurred in this country.

Forest fires in Spain

In Spain there are plant formations where fire is part of their natural dynamics, as is the case of the Mediterranean forest. However, forest fires affect various areas of the national geography.

Between 2000 and 2006, more than 900,000 hectares of the country were burned by forest fires. Between 2007 and 2017, there were more than 8,000 fire outbreaks per year and the actual fires exceeded 4,000 per year.

Forest fire in Teo (Spain). Source: Xosema / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

In 2017, more than 178 thousand Ha were affected by forest fires, including 56 large fires (more than 500 Ha in each case). The region most affected by forest fires is the Northwest (51.57%) and in the province of León (Encinedo municipality) more than 9 thousand Ha were affected.

Forest fires in Peru

Between 1973 and 2000, 117 large forest fires occurred in this country, affecting more than 122,000 hectares of forests. The annual forest fire rate increased from 30.7 Ha in the 70s (20th century) to more than 11 thousand Ha in the 90s, due to human causes.

Forest fires in Venezuela

In Venezuela, forest fires are recurrent during the dry season and about two thirds of its territory faces a high to very high risk. During 2016, more than 200 fires occurred in protected natural areas and in 2019 the number increased to more than 700 forest fires.

On the southern slopes of the Costa mountain range, the semi-deciduous forest has been substantially reduced and fires even affect the cloud forest. For its part, the Perijá mountain range on the border with Colombia suffered in 2016 the worst fire in 15 years.

Forest fires in Argentina

According to figures from the Ministry of the Environment of this country, more than 8.5 million hectares suffered forest fires between 2005 and 2017. One of the areas most affected by the fires is Patagonia.

In addition, about 30% of the Serranía de Córdoba areas are burned recurrently every year.

References

1. Aguirre-Briones, F. (2001). Forest fire training manual for crews. 2nd revised edition. Government of Aragon.
2. National Fire Management Center (2019). Fire management program. Close 2019. CONAFOR. Ministry of the Environment and Natural Resources. Mexico.
3. National Forestry Commission (2010). Forest fires. Practical guide for communicators. Mexico. National Forestry Commission (2013). Forest fires in Mexico. 2013 season.
4. INAMEH (2019). Early warning bulletin on the risk of forest fires for the Bolivarian Republic of Venezuela. Dry season 2018-2019. National Institute of Meteorology and Hydrology.
5. Manta, IM and León, H. (2004). Forest fires in Peru: a serious problem to be solved. Floresta.
6. Ministry of Agriculture and Fisheries, Food and the Environment (2017). Forest fires in Spain. January 1-December 31, 2017. Informative preview.
7. Mondragón-Leonel, MF, Melo-Ardila, A. and Gelvez-Pinzón, K. (2013). Causes of forest fires in the Caribbean, Andean and Orinoquia region of Colombia. Forest fire prevention through regional exercises linking the community and other local stakeholders that lead to the protection of forests and ecosystem services. International Tropical Timber Organization.
8. Navarrete, R., Oberhuber, T. and Reina, J. (2007). Forest fires. Practical manual. Ecologists in Action.
9. Vignote, S. (2020). Climate change and forest fires in Spain. Technical Report