Analysis 30 years after the Moratalla fire

Analysis 30 years after the Moratalla fire
Analysis 30 years after the Moratalla fire

Analysis of the severity of forest fires using vegetation indices. Case study of the 1994 fire in Moratalla (Murcia)

On July 4, 1994, a fire broke out in Moratalla that affected more than 30,000 hectares.

The Moratalla forest fire of 1994 is among the ten most devastating in the history of Spain

Juan Antonio Love

The municipality of Moratalla was the most affected by the forest fire that occurred on July 4, 1994. The burned area also affected other municipalities such as Calasparra, Cieza, Socovos and Hellín. This disaster burned a large part of the forest masses, affecting the Sierras de la Muela, Cerezo, Herrerías, Algaidón, Buho and Serratica within the municipality of Moratalla; Sierra del Puerto in the municipality of Calasparra; and finally the Sierra del Cabezo del Asno in the municipality of Cieza, and in the province of Albacete, the municipalities of Socovos and Hellín the Sierra de Maraña. These reliefs have altitudes between 200 and 1400 meters.

Forest fires are a major problem in the structure and dynamics of biodiversity in Mediterranean landscapes. They are characterized as one of the greatest environmental problems that exist.

It is worth highlighting the main factors on which fire depends to cause greater or lesser consequences on vegetation, starting from the amount of fuel, the meteorological conditions present at the time of the fire outbreak, to the type of topography of a given place.

Weather conditions are one of the most important factors that favour the spread of flames in a forest fire, so it is worth highlighting the climatic factors that occurred that day. The 1990s were marked by one of the worst droughts of the 20th century in the south-east of the Iberian Peninsula, with 1994 and 1995 being the most critical years, coinciding with the Moratalla IF. These types of climatic situations caused the low humidity in the vegetation to favour water stress in the plant cover. Added to this was the heat wave that affected the Region of Murcia during the days of the fire, making this episode of high temperatures the most intense since there have been climatic data in this area. In fact, most of the AEMET meteorological stations recorded values ​​above 45ºC on 4 July, coinciding with the same day the fire started. To this day, these records remain valid as the highest absolute values ​​recorded in the Region of Murcia, where temperatures reached 47.2ºC at the Murcia-Alfonso X (AEMET) station. The synoptic situation that triggered this episode of high temperatures was the result of the emergence of a very warm and dry continental air mass of tropical origin from the interior of the African continent. The characteristics of this warm advection had a temperature of 850 hPa (1500 metres above sea level) of 28-30ºC in the southeast of the peninsula, accompanied by strong dry south-southwest winds that made the efforts to extinguish the fire difficult.

The dominant plant formation within the burnt perimeter was the Aleppo pine, this species being the most affected. There were other formations such as holm oak groves, juniper groves, kermes oak groves, scrubland and esparto grasslands in the rest of the territory, these having a significant fuel load.

In the last century, Mediterranean forests were subject to excessive exploitation for human use, which would take advantage of forest resources. In addition, the soil was ploughed, removing vegetation for planting, turning the mountains into areas with a low risk of fire. After the rural exodus began in the mid-twentieth century, there was a significant abandonment of mountain areas, which helped the vegetation cover of the countryside and mountains to become more consistent. However, the limited exploitation of these, the abandonment of land and reforestation with flammable species has been reflected in the increase in forest fires.

The Region of Murcia has a total area of ​​11,313 km2, with 281.67 km2 being the area devastated by the Moratalla IF, that is, 2.48% of the province, demonstrating the magnitude of the fire.

Knowing the behaviour of these phenomena is important for the future, when it comes to mitigating fires or acting in one way or another in the recovery of forest masses. For this type of study, the use of Geographic Information Systems (GIS) and remote sensing has allowed us to have a database with an optimal spatial-temporal resolution to carry out work on the level of severity of forest fires.

The main objective of this master’s thesis has been based on the analysis of the degree of severity of the Moratalla IF in 1994, using satellite images belonging to Landsat 5 TM and Landsat 8 OLI, thus being able to carry out an exhaustive evaluation of the severity levels of the burn caused by the fire in the vegetation and in the soil. Different vegetation index calculations have been used, such as: Normalized Burned Area Ratio (NBR) to evaluate the degree of fire affectation, where -1 represents the burned areas and 1 those not affected by the fire; and the Normalized Difference Vegetation Index (NVDI), being able to carry out a multitemporal monitoring of the burned vegetation recovery after the fire, where values ​​close to -1 show the most depressed or unhealthy areas, and 1 represents optimal vegetation.

In this way, 30 years after this disaster, the regenerative capacity of the forests in this area has been demonstrated.

The first step is to delimit the affected area by analysing the information from satellite images based on a combination of spectral bands belonging to the post-fire. Using this method, it is possible to perfectly determine the difference between the green tones of the healthy vegetation surface and the brown and/or dark red tones referring to the burnt part.

It can be clearly seen in the image above that it corresponds to the days before the fire broke out (June 29) where the highest reflectivity of healthy vegetation is concentrated in areas of forest or irrigated land, standing out in an intense green color. However, the rest of the image is shown with poor colors, mainly due to the time of year in which it is located, with grayish tones, since during the summer period the vegetation is subjected to water stress. In the satellite image below, the post-fire scene is shown in false color, with the burned area being perfectly visible in reddish tones. This combination of satellite images ideally represents the burned areas, where healthy vegetation is distinguished from the affected vegetation cover surface.

Analysis 30 years after the Moratalla fire

Using photo-interpretation methods using the digitalisation technique, it has been possible to obtain the mask that represents the perimeter affected by the fire. In order to compare these results with those provided by official bodies, a previous surface area of ​​28,397 Ha had been calculated, compared to the 28,167.12 Ha obtained from this study. The difference between the data from official sources and those of this work are minimal (230.88 Ha), although this is probably due to the fact that the interior areas of the perimeter where the vegetation has not suffered any type of damage from the fire have not been discriminated.

Municipality Surface (ha) %
Moratalla (Mu) 20211,52 71,76
Calasparra (Mu) 3572,5 12,68
Cieza (Mu) 3198,92 11,36
Hellin (Al) 784,47 2,79
Socovos (Al) 399,71 1,42
Total 28167,12 100,0

A comparison has been made between the images after the fire and the current images, with the aim of checking the regeneration of the vegetation cover. As can be clearly seen in the image, the significant variation that has occurred on these dates where high vegetation growth predominates, coinciding mainly where the severity of the fire has been more important, representing a very high growth. With the NDVI indices, the evolution of plant regeneration up to the present has been checked, evidencing according to the data obtained a progressive increase in photosynthetic activity after the fire. After this, the NDVI spectral index showed null or very low values ​​of plant activity in pine forest areas to the west of the burned surface, while in the rest these values ​​had an average behaviour.

Analysis 30 years after the Moratalla fire

In the following image we can see the areas most affected by the fire, where we can see how the state of severity that prevails most in the area of ​​the fire is medium-low, with the yellow-orange colour predominating to a greater extent. It is true that in the western part of the study area the reddish tones stand out where the degree of severity of the fire has been high, dominated by those areas by forest masses of pine groves and sclerophyllous scrub par excellence. In general, these plant species have a very fast reaction to fire, burning very easily.

Analysis 30 years after the Moratalla fire

However, it is interesting to highlight the importance of this type of study within the environmental framework, since given the relevance of forest fires in the natural spaces of the Mediterranean, it has been considered appropriate to carry out this work, in order to verify the damage that fire can cause in a specific place and how that area can be affected in the future in terms of its plant regeneration, improving forest prevention and recovery management.

Several years after the fire, numerous forest regeneration actions have been carried out in the affected area, promoting the recovery of plant cover as well as the colonization of fauna.

 
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