0009-B3

The influence factors on the forest fire danger in Poland

Barbara Ubysz 1


Abstract

About 83% of the forest resources in Poland are subjected to fire risk and the forest fire increases continually. This paper presents the causes increase of the forest fire danger. The existing methods of the forest fire danger classification that developed in Poland and the last changes on the field were discussed. It was demonstrated the statistical data of the fires on high forest (number of fires, area burned, average area of fire, fire causes) in Poland's post-war fire history. Current changes in the causes of occurrence of the forest fires was determined. It was compared the fire danger in the state forests and in the privately owned forests. The forest fire danger increases particularly in the privately owned forests. These forest areas are not good prepared for fire event and firefighting. The example of the fire on the privately owned forests was described. It was carried out the analyze of the fire spread by means of the forest fire model that was developed by Szczygieł (1991, 1998). The forest fire protection system in the State Enterprise "State Forests" was demonstrated and estimated of their efficiency.


Forest fires danger causes

Forest fire is one of the most basic reasons of damage in the forest environment. Considering the growing tendency of forest fire number within the last few years as well as the magnitude of resulting loss, forest fires are still more frequently considered an ecological disaster.

Potentially, about 83% of the total forest resources in Poland are subjected to fire risk which - compared with the Europe's average respective figure equal 65%, gives the evidence of the undesired advantage of our country in this respect. The actually huge forest area endangered with fire: 7.2 million ha, has been the result of the below listed factors:

Another factor contributing to the elevated of fire danger and consequently the increased number and area burned of forest fires, is the more frequent occurrence of extreme weather conditions - facilitating forest fire, accompanied by rapid changes in atmospheric fronts. Moreover, the general climate warming and the warm and often snowless winters cause the elongation of the fire season: also winter and autumn months are becoming the increased fire season. An example may be given of the year 1999 in which the maximum intensity of fires (2106) was observed in September. The figure was seven times that observed in the period 1991-1995; the September of 1999 fires were more than one fourth of the year's fires.

Forest fire danger classifications

The factors described above have caused the alteration of particular forest types susceptibility to forest fire. Therefore, also the criteria of classification of particular stands and ascribing them to the forest fire danger classes, had to be changed. Earlier, the basic criterion was, as a matter of fact, site conditions under which the stand has developed. To the highest forest fire danger class included were those stands growing in the poorest coniferous sites (that is, the site of the arid coniferous forest and the fresh coniferous forest and the fresh mixed coniferous forest) covering about 65% of the whole forest area. As forest fire danger class moderate considered were the sites of: the moist mixed coniferous forest, moist coniferous forest and the mixed broadleaved forest (making together about 16% of forest acreage); fire danger class low was attributed to the rich sites (the boggy coniferous forest, the mountainous coniferous forest, the fresh broadleaved forest and alder carr - 19%). Beginning with year 1992, a new classification system has been introduced: except of site conditions, considered are: the actual age and crowns enclosure as well as the assessment of correctness of tending measures employed. The alteration has resulted in the incorporation to the highest class of the younger stands (up to 40 years of age) of loose crowns density growing on the sites earlier considered as belonging to the forest fire danger classes two lower (the richer varieties of the coniferous sites and broadleaf- and mountainous sites: humid mixed coniferous forest; mixed mountainous coniferous forest; mountainous coniferous forest; fresh mixed broadleaf forest; mountainous broadleaf forest; and mixed mountainous broadleaf forest). Similarly altered has been forest fire danger class moderate; also to this class included were stands 41-60 years old growing in some richer sites: fresh broadleaf forest; mountainous broadleaf forest; mixed mountainous broadleaf forest; mountainous coniferous forest and mixed mountainous coniferous forest. The new classification system of particular stands is to be employed for the local (micro-) scale: for forest compartment or a group of compartments. After the 1992 modifications (Santorski 1994), the classification - though potentially very useful at the scale of a Forest District - has not come to life. Its very detailed character allows for the improved awareness of the local forest manager of the more threatened parts of the forest, facilitating thus the undertaking of desired action.

At present, the only forest fire danger categorization binding in Polish forest has been that large-scale one (Instruction... 1996). In the system, the basic units are whole Forest Districts, National Parks, larger forest complexes or the Regional Directorates of State Forests. The ever first principles and 3-class forest fire danger system for Polish forest was made in the 70-es. This earliest solution gave the tool for the choice of adequate preventive action depending on the actual fire danger class (category). The subsequent growing change in the natural-forest condition and health status of forest stands were among the reasons that had participated to the necessity of the 1992 revision of the categorization principles and - consequently - the alteration of the forest fire danger zones borders (Santorski 1994). Following the revision, considered were not only those earlier employed factors: stand age and species composition, climatic condition (as characterized by the Sielaninov hydrothermic index), geographic context (presence of town agglomerations and industrial centers and the resulting intensity of tourism) as well as fire frequency; but also included was the factor of industrial pollution (SO2 and NOx pollution index). Those newly modified criteria made it possible to update the assessment of the potential forest fire danger in Poland and, besides, to present new maps of the fire danger categories of either particular Forests Districts or whole Regional Directorates of State Forests.

Statistical data on forest fires

Statistical data on forest fires in post-war Poland show a clearly growing tendency, both in numbers and burnt area (Fig. 1). The mean number of yearly occurring fires on high forest had doubled with in the decade 1981-1990. During the next decade it became three times larger than that observed in the period 1951-1960 (Tab. 1). The average yearly size of burnt area, after a temporary yet clear decrease - has risen again in the period 1991-2000. The mean area of a single forest fire in State Forests has diminished by more than two times in the same period (considering the 10-year intervals) or even more than 5 times, considering the 5-year periods. In the period 1991-2000 the total burnt forest area was 109,146 ha and the total number of fires was 83,061. Considering the last decade, the number of fires in State Forests equaled 47,190 events and was maintained at nearly the same level as that counted for the last twenty year period (1971-1990) - 47,390. The burnt area has only diminished by 12.5% in the last decade as compared with the previous period (the respective figures: 55,868 ha versus 63,960 ha). The number of forest fires in Poland contributed in 6 to 16% to the total number of forest fires in the whole of Europe. The yearly burnt area made from 0.80 to 9.68% (the latter recorded in 1992, the ever hardest year for Polish forest when the total burnt area on forest was 43,755 ha and the total number of fires was 11,858 and when at the biggest fire nearly 10,000 ha forest were burnt in Kuźnia Raciborska Forest District) of Europe's burnt forest area.

An alarming tendency has been observed in the last years: the continuously growing number of forest fires in forest owned by non-state owners, mainly in privately owned forest. The percent portion of such cases has risen rapidly from 15% in 1991 to 57% in the year 2000. In period 1991-2000 the burnt area in the State Forests and non state forests was nearly equal (the respective figures are: 55,868 ha versus 53,278 ha), and the average area of a single fire was in the latter more than two times larger.

Example of fire spread in the privately owned forests

The problem of fires in the privately owned forest may be illustrated by the example of the fire that took place on 21 May 1999 within the administrative borders of the Forest District: Sokołów and Łochów (Regional Directorate of State Forests in Warsaw) and covered an area of 162.43 ha. This fire extensive spread had been facilitated by the weather condition but at least in the same degree by the stands structure and the lacking preparation of the private forests for an event of fire (access roads and fire access roads, water supply points). The moisture of forest fuel (pine litter) dropped below the critical level: 15% at 9:00 A.M. and down 7% at 1:00 P.M. Szczygieł (1989, 1991, 1992) showed that approximately 90% of all forest fires took place when the moisture of forest litter was below 15%. The air temperature was on that day 25.2_ C (at 01:00 P.M.) and the relative air humidity dropped from 54% at 9:00 A.M. down the 32% level at 01:00 P.M. The weather parameters should be considered, thus, the fire weather (air relative humidity <46% and air temperature >22.4_ C) under which a majority of forest fires are being initialized (Szczygieł 1989). Noteworthy, the conditions favoring the emergence and development of forest fire depend predominantly on the actual moisture of the fuel; but the spread of the fire front has been, first of all, under the control of wind speed. On that day there was a strong gusty wind blowing with the mean velocity of 7.2 m/s at 01:00 P.M. (4.7m/s at 09:00A.M.) from the south-west in general, but of the varying direction. The changing direction of wind and its severe gusts had contributed to the widening of the fire front to still new directions which had finally led to the large area burnt and its envelope. Gusty winds of varying direction and velocity of 6-10 m/s are considered the most dangerous (Szczygieł 1989). Such conditions result in the frequent changes in fire spread and intensify the emergence of convection streams of air and its turbulence which is characteristic for the emergence of so called fire storms and facilitates the creation of new fire sources for long distances, even a few hundred meters.

The forest area where the fire took place were Scots pine stands growing in the poorest coniferous sites, aged 10-44 years, 2 to 14 m high, with heather, reindeer moss and poorly decomposed pine litter in the forest floor, all these had especially facilitated the very fast spread of the fire. Similar was the effect of the undergrowth (with juniper - Juniperus communis, containing the flammable volatile oil that had additionally facilitated the fire) as well as the poorly pruned stems of trees (with dead dry and flammable branching) of the scarcely growing and non-tended privately owned forest stands; they enabled the fire to reach the layer of crowns, and leading thereafter to the most dangerous crown fire. Another factor increasing the fire intensity was the age of the stands: in most cases below 40 years. And such young growth stands are particularly highly vulnerable to fire. The rapid character of the fire may be detected analyzing the increment of fire area: one hour after the fire initiation an area of 10 ha was burning, and less one hour later (after 103 minutes form the start): as much as 50 ha. The fuel loading was varying from 3 to 7 kg/m 2 .

The analysis of available meteorological data supports the opinion that the fire spread pattern was typical for such forest stands and given weather conditions. Table 2 present the analysis of fire spread conducted with use of the forest fire model constructed by Szczygieł (1989, 1991, 1998). The bold fonts denote the model data concerning those moments of the fire when assessed was the area of fire (from a plane) giving thus the opportunity to determine the mean spread rate of fire. Additional data connected with the mean velocity of fire front for the last - third- phase of the fire (hours: 14:00 - 19:00) are approximate figures obtained using the linear interpolation method. The mean spread rate of the fire front was equal for the last phase of the fire about 5.14 m/min (0.308 km/h).

Fire danger causes in the privately forests

At present, no legal restrictions are binding that would enforce the forest owner to undertake protection measures against forest fire, for forests or forest complexes below 100 ha of area. In fact, however, neither the larger privately owned forest complexes - despite the formal obligation to preventive fire control action - are prepared for a fire case. The regulation cannot be executed under the present day hard economic condition. Such obligations like, e.g., keeping observations and controlling the forest in order to reveal forest fire, ensuring the water supply for firefighting, the building and maintenance of access roads to the marked water supply points, the arrangement and maintenance of equipment bases for fire suppression, remain thus only a dead legal note.

All these circumstances have made that the private forests are, in the majority of cases, not at all prepared for the fire protection. Besides, the fact that forest complexes are owned by very many small owners does not facilitate the reaching of the fire protection aims. The area of 1.37 million ha of forest is owned by 1.4 million private owners. The small average area of a forest parcel does not allow for treating forest as the only or important income source. Not surprisingly, the owners themselves are not interested in paying for their properties protection and proper tending and only - in possibly highest profit from the harvested wood. No detailed management plans are being prepared for the forests not belonging to the state. The stands are very often in a very poor condition because of the non accomplished tending measures, which results in their increased susceptibility to fire and difficulties in fire control; moreover, such stands are often dangerous for the adjacent state forest. The above presented situation has forced the State Forests to at least partial accomplishment of the tasks of fire protection also in the private forests which leads to increased and still growing cost. The same is true connecting the building of water supply points for fire extinguishing, the building of access roads, performing the observations and patrolling forests, as well as accomplishment of fire suppression action, the use of airplanes etc. If the measures were not undertaken growing would have been the fire hazard also of those forests administered by the State Forests and the risk of large area fires leading to huge losses.

Forest fire protection system in Poland

The above presented statistical data give the evidence for the high efficiency of the complex system of forest fire protection that has been operational for years in the State Forest of Poland. The system contains, among other, the following solutions in the field of fire protection of forest area:

1. criteria and principles of classification of forest stands and forested areas to particular classes of forest fire risk,

2. the methods of assessment of forest fire risk (including the forecasting of the fire risk of considering the actual weather forecast - Szczygieł 1991, Wiler 2000),

3. the principles of the information-warning activity,

4. the organizational-technical background of preparation of the organizational units of state forests for fire suppression in the fields of:

The homogenous state purse ownership form is undoubtedly a plus that facilitates the organizational solutions. State owned forests contribute in 78.4% to the whole of Polish forests (Fig. 2). This situation facilitates the co-ordination, proper functioning and financing, e.g., financial support to the unprofitable forest area, joint financing of airplanes used in the patrolling and fire extinguishing.

Indisputable is the fact that the private forests are still more often subjected to fire which accompanied by the still actual yet unsolved question of future privatization and re-privatization of today's state forests, makes the above presented matters a hot topic. The possible danger that could emerge in the future in the field of forests fire control cannot be overestimated. It is estimated that, following the possible decisions altering the present legal status of our forest, its major part (71.2% or 4. 891 thousand ha) of now state forests owned by the State Purse and administered by State Forests will change its ownership status. Under such circumstances one cannot expect a significant improvement, on the contrary: at least temporary worsening is to be expected. In the environment of market economy, it is the forest owner that takes decisions on the aim of forest management within the framework of legal regulations, and this aim is, first of all, income maximization. If so, an impulse that may force the private owners to the joint effective action aimed at fire control, may only be given by either disastrous forest fires and the transformations (putting a tax on forest resources - following the example of other countries) enabling forest management to become the main income source.

Current changes in the causes of forest fires in Poland

Among the forest fire causes in Poland, growing has been in the last years the consequences of fire transfer from the meadows and plant residuals subjected to burning to the forest and, also, the deliberate commitment of arson. The tradition to burn meadows, despite the legal restriction and appeals to the public repeated every year, has still been a serious problem every spring. Burning grasses are dangerous for forests and for farms; often they lead to people's deaths - including the perpetrators themselves. The smoke creates a serious danger for drivers by reducing the visibility. The drivers themselves may also produce forest fire by leaving gloving cigarette-ends. In the season of meadow burning the number of forest fires rapidly grows: even five times. Every year, hundreds of hectares of meadows and near-road ditches are being burnt (Fig. 3). In 1996 - the maximum number of fires were initiated in the non-forest grounds: 28% of all forest fires in the State Forests were because of the transfer from the non-forest grounds. The increase was nearly five-times as compared with the period: 1991-1995. In April 1996, that is the typical period of grasses burning, there emerged 66.5% of all the forest fires, and their area has contributed in 90.1% to the yearly total burned area. It is nearly impossible to explain to the farmers that their belief in the "advantageous" effect of dry grass burning for the soil fertility is not justified. The wide action aimed at the change of farmers' attitude are not always fruitful. One example of an effective action should be mentioned here; the idea to prepare special informative-propaganda materials for the priests from the especially threatened regions - to be utilized while preaching a sermon. The good starting point would be the excerpts taken from the letters of saint Peter and the teaching of saint Francis from Assissi. Such precepts, addressed directly to the conscience of farmers - perpetrators of arson - from the side of priests (often still the only accepted authority for the village people) have proved unexpectedly highly effective. Another action was arranged for the town people - often owners of allotments: an early spring happening performance. A painting showing the beauty of nature was made that was at the end of happening burnt.

Another very important cause of fire are still deliberate commitment of arson, both in the state forest and the non-state forest. In period 1991-1996 the share of deliberate arson in the State Forests was 26.3% (the number of fires) or 17.4% (their area); in the next two years (1997-1998), the respective figures were: 46.0% or 47.9%. In the period of economic transformation, new causes of forest fire may be observed. Earlier, psychological malfunctions of the perpetrators were among the main reasons of arson commitment. At present, important has become also the economic motifs. Two social-occupational groups representatives are among those committing arson in forest. For both, arson commitment is either the only possibility of making an extra income or, even, the only possibility to earn any money during the hard period of transformation. One of them are firemen (members of the Voluntary Fire Department units) who are paid for their direct participation in the fire extinguish actions and if so - they may be interested in more frequent fires. The cost of economic transformation is, unfortunately, very high, and a large part of society are becoming pauperized. And this forces people to committing so desperate activity. The other group of perpetrators is recruited directly from the unemployed people or, even, late forest workers fired in the result of the re-structurization. Such people - nowadays being even employees of private forest firms - are also interested in the increased demand for forestry labor - e.g. in the field of removing the fire residuals. The desperate people do not pay much attention to the results of their activity. This is especially evident in the regions of so called structural unemployment.

References

Annual statistic reports of fire protection and of fire and losses, 1978-2000, National Headquarters of the State Fire Service.

Information and elaboration statistic: Forestry, protection of environment 1988-2000, Warsaw [in Polish].

The Instruction for the fire protection of forest areas, 1996, MOŚZNiL, DGLP, Warsaw [in Polish].

Santorski, Z., 1994. Regionalization of forest fire danger in Poland. Ph.D. Thesis, Forest Research Institute, Warsaw [in Polish].

Szczygieł R., 1989, Forest surface fire spread - modelling attempt, Ph. D. Thesis, Forest Research Institute, Warsaw. [in Polish].

Szczygieł, R., 1991. A model of fire forest. 10éme Congres Forestier Mondial, Proceedings actas No. 2, Paris.

Szczygieł, R., 1991. Meteorological factors and forest fires. Scientific Fascicles of the Main Schools of Fire Service No. 1, Warszawa.

Szczygieł, R., 1992. The influence of weather factors on forest fire risk. Proceedings of Seminar of Forest Fore Prevention, Land, Use and People. Athens, Greece 27 October to 3 November 1991, Seminar ECE/FAO/ILO. Published by Ministry of Agriculture Secretariat General for Forest and National Environment.

Szczygieł, R., 1998. A model of forest fire. Proceedings of Symposium CTIF "Firefighting and risk coverage". Lisbon.

Wiler, K., 2000. Forest fire protection. SA PSP, Poznań [in Polish].

Table 1. Statistical data of fires on high forest in Poland in the period 1951-2000

Period

Mean yearly

number of fires

area burned [ha]

average area of fire [ha]

total

in State Forests

total

in State Forests

total

in State forests

others

1951-1955

 

1609

 

5069

 

3,15

 

1956-1960

 

1344

 

2946

 

2,19

 

1961-1965

 

1298

 

2641

 

2,03

 

1966-1970

 

1569

 

1822

 

1,16

 

1971-1975

 

2094

 

2708

 

1,29

 

1976-1980

 

1757

 

2610

 

1,49

 

1981-1985

2799

2627

4469

3871

1,60

1,47

3,49

1986-1990

3419

3001

4389

3603

1,28

1,20

1,88

1991-1995

8364

5206

13818

8673

1,65

1,67

1,63

1996-2000

8248

4232

8011

2500

0,97

0,59

1,37

1951-1960

 

1477

 

4007

 

2,71

 

1961-1970

 

1434

 

2232

 

1,56

 

1971-1980

 

1925

 

2659

 

1,38

 

1981-1990

3109

2814

4429

3737

1,42

1,33

2,35

1991-2000

8306

4719

10915

5587

1,31

1,18

1,49

1951-1980

 

3223

 

2966

 

0,92

 

1951-1990

 

3120

 

3159

 

1,02

 

1951-2000

 

2474

 

3644

 

1,47

 

1961-1980

 

1690

 

2563

 

1,52

 

1961-1990

 

2065

 

2954

 

1,43

 

1961-2000

 

2728

 

3612

 

1,32

 


Table 2. Analysis of fire spread in the 1999 fire in Forest Districts Sokołów and Łochów

Hour

    Fire duration

Duration of perimeter phases of fire

Total fire area

Fire area in particular phases

Total perimeter of fire

Fire perimeter in particular phases

Mean rate spread of fire front in particular phases

 

[min]

[min]

[ha]

[ha]

[m]

[m]

[m/min]

[km/h]

12.00

0

Fire emergence: 21May 1999

13.00

60

60

10

10

1186

1186

8,1

0,486

13.43

103

43

50

40

3555

2369

22,6

1,356

14.00

120

17

56

6

4492

937

22,6

1,356

15.00

180

60

108

52

7185

2693

18,4

1,104

16.00

240

60

139

31

9264

2079

14,2

0,852

17.00

300

60

155

16

10757

1493

10,2

0,612

18.00

360

60

161

6

11665

908

6,2

0,372

19.00

420

60

162

1

11987

322

2,2

0,132



1 Department of Forest Fire Protection. Forest Research Institute.
00-973 Warsaw, 3 Bitwy Warszawskiej Street, Poland
tel. +(48 22) 715 04 24, fax +(48 22) 715 04 22,
e-mail: B.Ubysz@ibles.waw.pl
http://www.ibles.waw.pl