Fire environment, fire regimes and ecological role of fire
Mexico has a total area of 1,967,183 km2 and a forest area of 141.7 million hectares, of which 56.8 million hectares are temperate forests and tropical forests and 58.4 million hectares are zones with arid and semiarid vegetation.
The forest fire season normally occurs between January and July. March and April are the major fire months because they coincide with the dry season. Human activities cause 97 percent of the wildfires, with agricultural and cattle activities causing 54 percent of the fires. In tropical zones, the main cause of fires is the practice of slash and burn agricultural practices. Burns to improve grass conditions for cattle are the main cause of intemperate forests. Ninety-five percent of the fires burn on the surface, affecting mainly herbs, shrubs, and grasses.
The average number of wildfires for the 1990-1999 period was 7,767. These fires affected a total surface area of 251,697 hectares (a national average of 32 hectares per fire).
Fire regimes can be described in terms of how severe they burn and how much they change the vegetation that burned. Fire regimes can be classified in the following terms:
Understory fire (applies to forests and woodlands)–fires are generally non-lethal to the dominant vegetation and do not substantially change the structure of the dominant vegetation. Examples include pine communities and pine-oak communities.
Stand-replacement fire (applies to forests, woodlands, shrublands, and grasslands)–fires kill aboveground parts of the dominant vegetation, changing the aboveground structure substantially. Approximately 80percent or more of the aboveground dominant vegetation is either consumed ordies as a result of fires.
Mixed-severity fire (applies to forests and woodlands)– the severity of fire either causes selective mortality in the dominant vegetation, depending on different tree species’ susceptibility to fire, varies between understory and stand replacement.
Non-fire regime–little or no occurrence of a natural fire. Examples include montane rainforest and tropical rainforest.
A forest fire is considered to be any fire which affects forest vegetation by natural or human causes, and occurs and spreads in an uncontrolled manner.
Narrative summary of major wildfire impacts on people, property, and natural resources that occurred historically
The average number of fatalities due to wildfires is 2 persons per year.
Forest fires mainly cause mortality to natural regeneration in temperate forest zones, causing economic loss from the affected trees.
In tropical areas wildfires enhance the growth and spread of a fern (Pteridiumsp.) that contributes to rapidly spreading and difficult to control wildfires (Fig.1). In tropical forests, wildfires affect biodiversity, wildlife, and the ecology in general. However, people also deforest tropical areas as they look for agricultural alternatives.
Narrative summary of major wildfire impacts on people, property and natural resources during 1990s
During the 1990s, Mexico had a drought of seven consecutive years(1994-2000). In 1998, El Niño caused one of the most severe droughts, creating the most difficult wildfire season in Mexicos history. Mexico had14,445 wildfires affecting 849,632 hectares–the largest area ever burned in Mexico in a single season.
Because of the large fires that occurred in 1998, 72 people died during fire control activities.
In order to control the widespread wildfires, it was necessary to gain support from the military, (SEDENA), State Governments, many federal agencies, and volunteers. Mexico also received valuable support from the United StatesGovernment in terms of equipment, technical support, and financial resources.
In 1998,18helicopters of different types and an air tanker were used; and17,000firefighters were transported. The helicopters dropped 15.1million liters of water and foam on the fires.
Due to the large area burned by wildfires in 1998, actions were taken for reforestation, soil and water conservation, and natural regeneration. Eighty-five areas were selected in 21 States to restore 188,288 hectares through reforestation.
Figure 1. A forest fire in Lagunas de Montebello National Park in 1998 resulted in the widespread establishment of bracken fern.
Fire management organization used in Mexico
Fire prevention and control are a Federal responsibility and take place through the Secretary of Environment, Natural Resources, andFisheries (SEMARNAP). SEMARNAP has 32 state delegations distributed throughout the country with personnel, crews, equipment, and infrastructures.
SEMARNAP has about 2000 firefighters, more than 200 vehicles, about 800 radios, and the tools and equipment necessary for fire control. Thirteen Type II helicopters are rented each year on the average. To control forest fires SEMARNAP receives support from the military, other federal agencies, state governments, and volunteers.
National programs of wildfire prevention, detection, and control are prepared each year. These programs establish different actions, with emphasis on risk areas and critical zones.
Fire prevention programs are designed to inform people about being careful with fire. Television, radio, posters, booklets, flyers, and press conferences are used to communicate fire prevention messages to the public.
Firebreaks and prescribed burns are used to help limit the spread of fire and reduce the fuel hazard.
Watchtowers, ground detection, commercial aircraft reports about forest fires, aerial detection, and satellite detection are all valuable resources used in the detection of fires.
Canada provides support with maps about fire danger indexes based on the assessment of vegetation, temperature, humidity, etc. The danger rating system permits the prediction of fire risk and fire behavior.
Table 1. Number of fires and area burned, 1990-1999
The database is managed by computer and paper records. Average annual fire size: 32 ha per fire.
Use of prescribed fire to achieve resource managementobjectives
The use of prescribed burns and control lines (firebreaks) were intensified in the 1990s, mainly through training courses, to reduce the presence of risky fires. More than 59,000 hectares of prescribed burns and10,500 kilometers of control lines were completed annually on the average. These practices have been carried out in forests where people burn grasses for cattle and in places where there are large accumulations of fuels
Public policies affecting wildfire impacts
Because the major wildfire causes are agricultural and cattle activities, SEMARNAP and SAGAR (Secretary of Agriculture, Cattle, andRural Development) published a Fire Standard, which recognizes that peopleare using fire in agricultural and cattle practices; and provides norms for its proper use (Fig.2). One of the most important issues in this standard statesthat farmers must build control lines when they use fire for their activities.
Another important policy is the promotion of programmes of economic incentives and agricultural alternatives to motivate people to avoidthe use of fire as a tool. These actions are accomplished with the execution oftheprogramme named Productive re-conversion.
Also, television and radio spots are used to induce peopleto avoid the use of fire and to report detected wildfires to the toll free telephone lines.
Sustainable land use practices used in Mexico to reduce wildfire hazards and wildfire risks. Commercial exploitation of natural forests in Mexico is carried out with a Management Programme. This programme contains the necessary information and issues to practice sustainable forest management. Usually these forests have a low occurrence of forest fires becausethe owners get economic income from forests.
Figure 2. In1998, many agricultural fires were free-burning, often escaping into adjacent forests.
In forests with cattle activities the vezade invierno programme is implemented. Viciavillosa is a leguminous plant used to feed the cattle and reduces the needto use fire within these zones.
In tropical forests, different alternatives with economic support from government take place (the Agricultural Sedentarisation and Enhancing plantations on second growth tropical forests are two examples).
In another tropical zone, different practices are usedlike perennial cultivation and agro-forestry systems to keep land in constant production and diminish the need to practice slash and burn agriculture.
In 1999 the Federal Government executed the programme named Temporary Employment Programme. This programme basically consists in making new job opportunities by building control lines in low-income non-productive forest zones. This programme has diminished the presence of wildfires in the zones where it has been implemented.
Community involvement in fire management activities
Since the extraordinary presence of fires in 1998, people have been made aware of the risks that wildfires represent and the damage theydo to wildlife, vegetation, and the environment (Fig. 3).
Figure 3. SEMARNAP officers conducting a public fire prevention meeting with people from Zinacantan (Los Altos de Chiapas) in 1998. Note the hazy atmosphere from nearby fires.
Today nine different federal agencies, state governments, and municipalities work together with SEMARNAP on wildfire prevention andcontrol.
Common people and land proprietors have an important role to play in the protection of Mexico’s forests from wildfire. The media also has an important educational role to play in transferring information to variousaudiences.
During the fire season, a widespread awareness programme is implemented using television, radio, and printed material. People reportdetected wildfires to the Wildfire Prevention and Control National Center.
Note: This paper is the official contribution to the FAO Global Forest Fire Assessment 1990-2000.