Cartography of Forest Fires Recorded in Central Portugal from 1983 to 1989

Int.Conf. FOREST FIRE RESEARCH Coimbra (1990) - Proceedings CARTOGRAPHY OF FOREST FIRES RECORDED IN CENTRAL PORTUGAL FROM 1983 TO 1989 LUCIANO LOURENÇO & A. BENTO GONÇALVES lnstituto de Estudos Geográficos, Faculdade de Letras , Universidade de Coimbra, Coimbra, Portugal. SUMMARYl One of the most practical indirect ways to relate the set of all the factors involved in the forest fires problem, is through the cartography. This representation translates not only its result but also identifies the places and dates of occurrence besides the self spacial extension of the phenomenon, also carrying on, its geographic site. The cartography, both of the forest fires number and of the burned areas, provides a very good information about the different aspects to be considered, either on prevention terms or about the forest fires fight. In this way, the cartography of the forest fires, besides reflecting the sensibility to the fire of the different regions, it also translates the conjugation and, simultaneously, the degree of activity of all the intervening variables in the forest fire phenomenon, for that reason its analysis is extremely important. INTRODUCTION This work corresponds to an actualization of the communication presented, in November of 1988, to the Scientific Journeys on Forest Fires (L. LOURENÇO, A. BENTO GONÇALVES & H. SOARES, 1988). It was re-elaborated according to what was then proposed not only in terms of an enlargement of the analysis period, by including the years of 1988 e 1989, completely different from each other, either on the fire numbers or on burned extensions, but also by the enlargement of the area then considered, being included 17 municipalities at North. We intended to include all the area correspondent to the Inspecção Regional dos Bombeiros do Centro, but the absence of elements about forest fires for 12 municipalities at South, did not allow their study. l This text corresponds to an adaptation of another text, entitled "Representação Cartográfica dos Incêndios Florestais ocorridos em Portugal" (inpress). A.08- 1 METHODOLOGY Firstly we gathered the available information about the forest fires in the Direcção-Geral das Florestas, and in the Circunscrições Florestais of Coimbra and Viseu, and in the Centros de Prevenção e Detecção de Incêndios Florestais of Viseu, Lousã and Sertã After organizing and processing, statistically, those informations we carried on to their cartography. We choose the graphic presentation instead of extensive numerical tables, because the cartography, being visual, allows a better understanding of the forest fires phenomenon. For that purpose, we have considered the country divided into three large regions: North, Centre and South. The limits, for practical reasons, from the point of view of the statistic information's organization, made them correspond with the administrative divisions of the districts or of the municipalities. In this way, the North Region coincides with the five districts located at North of the Douro River. The Centre Region, practically located between the Douro and Tejo Rivers, corresponds to six districts, and the South Region, the largest one, is composed by seven districts. As the region most affected by the forest tires coincides with the center of the Country, it deserved a more detailed treatment, having been considered, at a municipality’s level, the different elements relative to the Circunscrições Florestais of Coimbra and Viseu. Some of that data is out of date but is considered because it is the only one available. Referring to the forest tires, the years from 1983 to 1989 were studied. RESULTS CHARACTERIZATION ATA GENERAL LEVEL Leaving out the years of 1974 and 1975, it was, only, after 1978 that the problem of the forest fires became worse and, particularly, in the North and Centre regions. From the three defined regions, the Centre was the most affected by the forest fires, not only in quantity but also, and mainly, by the large extensions covered by the fire. The comparison between the different aspects common to the three regions make prominent the inter-regional contrasts, at same time that, on aspects regarding the forest tires, give prominent significance to the Centre Region. Thus, regarding only its surface, we have verified that the South occupies nearly half the area of portuguese Mainland. The same has occurred when we considered the whole surface occupied by forest and by uncultivated lands, most of them having forest aptitude and, therefore, we verified that the South has remained in the first place, but was closely followed by the Centre. A.08- 4 Considering proportional areas, i.e., comparing the surface occupied by forest and by uncultivated lands with the area of each region, we have observed that the Centre Region began to distinguish itself from the others, because almost 63% of its area has forest aptitude. lt was succeeded by the North and then by the south with less than 10% of its surface occupied by forest and uncultivated lands. Comparing, now, this values with the average number of forest tires in each of those regions, we have confirmed, curiously, a certain approaching between them. With regard to the areas annually burned, it was observed that, on an average, near 70 & of them corresponded to the Center, 20% to the North and a little more than 10% to the South. This values imply that, annually, near 22, 10 and 3%, respectively, of those regions were destroyed by the forest rues. The spatial distribution, on average terms, both of the forest fires number (fig. 1) and of the areas covered by the tire (fig. 2), is a good illustration of the contrast and of the relative importance of this phenomenon in each of those three regions. Fig . 1 - Spatial representation of the annual Fig. 2 - Spatial distribution of the average area average number of fires in each region. annually burned in each region (ha). CHARACTERIZATION AT A LOCAL LEVEL (MUNICIPALITIES) As the Centre Region showed a greater sensibility to fire we have tried to define, inside it, sub-regions with similar characteristics, on forest fires terms, processing for that purpose the information available at a municipality’s level (fig. 3). On surface terms, generally, the interior municipalities are the ones that present the largest areas. In the first place come the municipalities of Castelo Branco and of ldanha-a-Nova, succeeded A.08- 3 much after, regarding that the following class has not effectives, by the ones of Guarda, Sabugal, Covilã and Pombal, the unique county of the coast. Fig. 3 – Spatial localization of the municipalities. A.08- 4 Legend: A.08 - 5 The municipalities of reduced dimension are the most frequent, mainly in the coast and in the septentrional half of the interior, since in its south half prevails, as we saw, the ones of great dimension. When we analyzed the municipality forest area we have verified that, generally, they have presented an almost direct relation with the municipal areas, i.e., the largest municipalities confined the largest spot of forest, which do not always imply that they have denser forests. It was in the municipalities that make the transition from the coast to the interior that, generally, we have found the greatest densities, i. e., in the municipalities that, roughly, extend themselves through the Cabeço Rainha, Alvelos, Lousã, Buçaco, Caramulo, Arestal, Freita, Arada and São Macário mountains (fig. 4). The superficies occupied by non-cultivated lands, full of pasturage and brushwood and, therefore, plenty of fuel, prevail in the interior municipalities concurring with the Raia region. As these are the most extensive municipalities, no wonder that they have the greatest surfaces of uncultivated lands. o 6 to 20 D 20 to 33 D. 33 to 47 rn 47 to 60 60 to 74 Fig. 4 - Municipalities distribution of the arborization rates (%). • A.08- 6 Nevertheless, considering the areas occupied by non-cultivated lands, comparatively with the areas of the respective municipalities we have verified that the highest rates corresponded to the municipalities that coincide with the mountainous regions, as occurred with the ones of Arouca , Manteigas, or even, with the one of Porto de Mós. We have observed ·that the municipalities belonging to the mountainous groups of the Cordilheira Central (Central Ridge) and of Gralheira, as well as the plateau areas plateau that serve as connection to them and that extend themselves between the mountains of Nave, Marofa and Mesas, showed the highest rates of uncultivated lands (fig. 5). After considering the spatial distribution of forest and of uncultivated lands, the spots that can provide fuel to the forest fires, it might be logical to accept that the distribution of the latter ones was similar to the distribution of the former ones. However, considering the annual· average of forest fires recorded in each municipality, we have verified that its distribution depended, also, upon other factors, both of physical order and of human nature. o O. to 10 o 10 to 20 o. 20 to 30 m 30 to 40 lil 40 to 50 Fig. 5 - Distribution of the rates of uncultivated lands, by municipalities (%). A.08 - 7 Indeed, the highest number of fires was recorded in the municipalities of Viseu and Covilhã, did not correspond to the greatest spots of material fuel, but to the existence of strangleholds that made difficult the increase of t4e populacional agglomerates. In the same way it is strange that the municipalities of Figueira da Foz and of Pombal have registered a high average number of forest fires that, surely, will reflect the importance of the humain nature's reasons better than the ones of physical order. Notwithstanding, luckily, most of the municipalities recorded an average number of fires relatively low, when compared with the number verified in Viseu. The municipality that, in average, had 234 fires by year, i.e., 2 forest fires by day, throughout the whole "fire season" (fig.

Load more