DEGRADATION Of DOLINES ON LOGAŠKO POLJE (SLOVENIA) DEGRADACIJA VRTAč NA LOGAŠKEM POLJU (SLOVENIJA) Mateja BREG 1 Izvleček UDK 551.435.8:551.44(44) Mateja Breg: Degradacija vrtač na Logaškem polju (Slovenija) Kot primer dolgotrajnih antropogenih posegov v kraško geomorfologijo je v članku predstavljeno Logaško polje, na območju katerega je zadnjih petdeset let potekala zelo inten- zivna degradacija vrtač. Na 604 ha velikem vzorčnem območju izvedena analiza letalskih posnetkov iz različnih obdobij (leto 1944 in 2000) je pokazala, da je 77,5 % vrtač (441 od skupno 569) popolnoma izginilo. V glavnem so bile zapolnjene z različnim odpadnim materialom (izkopni material, komunalni, industrijski in gradbeni odpadki) ali pozidane, 22,5 % (128) vrtač je bilo le delno pozidanih in preoblikovanih oziroma so se povsem ohranile. Ovrednotili smo številne antropogene dejavnike, ki so pomembno preoblikovali vrtače. Kljub temu da je vrtača tipična geomorfološka oblika kraške pokrajine, se tako v javni (krajevni ali državni) kakor strokovni sferi pre- malo pozornosti posveča njihovemu ohranjanju in zaščiti. Ob upoštevanju paradigme sonaravnega trajnostnega razvoja je treba pokrajino in reliefne oblike kot del zemeljskega površja opredeliti kot neobnovljivo naravno dediščino oziroma kot neobnovljiv naravni vir. Ključne besede: geografija, vrtača, neobnovljiv naravni vir, de- gradacija, zaščita, sonaravni razvoj, Logaško polje, Slovenia. 1 Anton Melik Geographical Institute, SRC SASA, Gosposka 13, 1000 Ljubljana, Slovenia; e-mail: mateja.breg@zrc-sazu.si Received/Prejeto: 30.01.2007 COBISS: 1.01 ACTA CARSOLOGICA 36/2, 223-231, POSTOJNA 2007 Abstract UDC 551.435.8:551.44(44) Mateja Breg: Degradation of dolines on Logaško polje (Slo- venia) As an example of long-term human intervention onto karst geo- morphology, the article deals with the area of the Logaško polje, where degradation processes of dolines have been very intense during the last fifty years. The analysis of aerial photographs from different periods (years 1944 and 2000) was carried out on a study area of 604 ha. It showed that 77.5 % of dolines (441 of total 569) have completly disappeared mostly by being filled up with different waste materials (excavation material, municipal, industrial and building waste etc.) or they were built up while 22.5 % (128) of dolines have been entirely or partly preserved. Several anthropogenic factors that had an important influence on doline-changes are being evaluated. Despite the fact, that doline is a typical geomorphological feature in karst landscape the public (local or state) and the scientific sphere pay little at- tention on their geomorphological preservation and protection. Considering the paradigm of sustainability, the landscape and its landforms, as they are part of Earth’s surface, would need to be classified as a non-renewable natural heritage or even non- renewable natural resources. Key words: geography, doline, non-renewable natural resource, degradation, protection, sustainable development, Logaško polje, Slovenia. INTRODUCTION Landforms are among the most widely-spread and spec- tacular natural, non-biological features: dolines, river gorges, mountain peaks, natural bridges, maritime cliffs and others. They have always raised attention as attrac- tive elements of the landscape but not only does the vis- ual aspect of the landscape determine the importance of landforms, so does its cultural role. Besides that, the sci- entific, educational and research aspects have to be con- sidered as well (Panizza and Piacente, 2003 in: Panizza, 2003). While using natural resources man has for centuries selfishly subdued landscape and nature and transformed ACTA CARSOLOGICA 36/2 – 2007 224 them in accordance to his needs. Cultivated dolines have been the site of various traditional activities (arable farm- ing, gardening, pasturing, water supply etc.). In some Slovene areas (Kras, Bela krajina, Matarsko podolje etc.) these activities have survived to a smaller extent while in other places subtle cultural elements, such as dry-stone walls, speak of their past presence. Despite the apparent usefulness of dolines there had often been a desire among the inhabitants of karst regions, particularly in agricul- tural areas, to fill them up. Many dolines today are filled up with different kinds of unknown waste material, covered with variable thick layers of cover-material or simply overgrown by vegeta- tion. Waste materials (municipal, construction, indus- trial waste etc.) deposited in nature represent the most irresponsible activity affecting the karst features and pro- cesses that at one point became subject to degradation processes that had not only had a great effect on karst hydrology or ecology but also permanently influenced karst landforms and the entire landscape. STUDy AREA AND WORKING METHODS We have studied the North-East part of Logaško polje (map 1) where several dolines had been formed mainly on limestone bedrock (dark-grey limestone and grained dolomite) and river or stream deposits (Buser et al., 1967). At the moment, the Logaško polje is under the big- gest environmental pressure as several socio-spatial fac- tors (proximity of Ljubljana, good transport connections, lower rents etc.) have caused immigration to its largest urban centre, Logatec (7616 inhabitants (SURS 2002)), and its surroundings. f urthermore the proximity of the motorway and a double track railway have stimulated the development of the secondary and tertiary activities and the expansion of the business-industrial zone. The comparison of available aerial photographs from different periods can show how unsustainable the dealing with dolines had been over the last decades. The map 1: Logaško polje is located in the south-western part of Slovenia. MATEJA BREG ACTA CARSOLOGICA 36/2 – 2007 225 artificially defined test-area measures 604.8 ha (6.048 km²) and coincides with the surface of two partly cover- ing digital b/w aerial photographs from 1944 (spatial res- olution 1200 dpi). Archive aerial photographs from 1944 are the oldest known aerial photographs of the studied area and represent the starting point for the analysis of dolines-changes till the year 2000. The origins of the aer- ial photographs from 1944 are allied aerial observations during World War II. The documents are being kept in The Aerial Reconnaissance Archive (TARA) - University of Keele in the United Kingdom. The records are avail- able in digital form but need to be georeferenced and their quality (colour, contrast, transparency) adjusted to get as much useful information as possible. We have georeferenced the aerial photographs and adjusted them with the coordinate system DOf5 (Digital orthophoto image, scale 1 : 5000, Gauss-Krüger coordi- nate system). Based on selected old and new control point coordinates (buildings, junctions etc. that are present on both photographs) the computer program calculates the transformation parameters. The function contains for- mulas of linear mapping, un-linear mapping and the least squares method (Petek, f ridl, 2004). The photointerpretation of the old aerial photo- graphs and of the recent digital orthophoto (map 2) made it possible to digitalize the dolines (polylines) of the stud- ied area at two points in recent history. The database was edited with separate attributes for each photograph. The identification of dolines and their main characteristics was based upon a photointerpretation-key that included following parameters: shape, depth (shadows give an im- pression of depth), colour (different shades of grey - the darker ones usually mark the bottom of dolines), texture. Attributes for each doline were defined with the help of visual photointerpretation and analysis. f or the year 1944 the location, shape and dimension of each visible doline were determined and at the same time their actual pres- ence was checked on the more recent photograph from the year 2000. Both sources served furthermore for iden- tifying accessibility and land use of dolines. The gained data was statistically analysed. map 2: Aerial photographs of study area in the years 1944 and 2000. DEGRADATION Of DOLINES ON LOGAŠKO POLJE (SLOVENIA) ACTA CARSOLOGICA 36/2 – 2007 226 On the aerial photograph from 1944, 569 dolines were evidenced and their shape, dimension and surface-cover determined. The spatial spread of dolines in the studied area is connected to its geologic structure: on limestone, dolines are larger and more concentrated, on fluvial de- posits they tend to be smaller whereas there are almost none in the areas with dolomite bedrock. Dolines cover approximately 28.9 ha (0.288 km²), which represents 4.8 % of the total surface of the studied area. The aver- age dimension of a doline is 507 m². The comparison shows that between the years 1944 and 2000 77.5 % of dolines (441 of total 569) have completely disappeared - in most cases they were being filled up with differ- ent waste materials (excavation material, municipal and building waste etc.) or they were simply built up. f urthermore 22.5 % (128) have been entirely or partly preserved (partly built up). On map 3 red polygons mark the dolines which have not been preserved between the years 1944 and 2000, yellow polygons mark the partly preserved dolines and green polygons mark the preserved ones. Among the first to change the surface morphology were farming activities, most notably agriculture. The most important were agro-tech- nical operations that were carried out in the lower part of the Logaščica stream basin in the year 1986 and continued in years 1987/88 on Pus- to polje (in English: Bleak (empty) field). The prevailing process, that changed the landscape-morphology, was the filling up of dolines with soil, rock- and excavation material from other locations. f or this purpose 12,000 m³ of material from an old railway embankment, dating from World War I, was used. At the same time municipal landfills in dolines, including industrial landfills with dangerous waste, were being covered (Bricelj, 1988). The agricultural use of the doline’s floor is conditioned by its shape and depth that defines the pos- sible cultivation. Dolines covered with meadows (meadow-dolines) are usually cultivated in its entirety (bottom and slope) while the fields are usually located on the bottom of dolines and their flatter parts re- spectively. f ield-dolines are best used if filled up and levelled to the surrounding height. Since the floor of dolines is mostly narrow the fields there are smaller, so in order to in- crease the arable land, dolines were filled up. A field on a greater surface consequently enabled a greater har- CHANGES Of THE NUMBER AND LAND USE Of DOLINES IN THE LAST f IVE DECADES map 3: Dynamics of the dolines-changes in the period 1944 – 2000. MATEJA BREG ACTA CARSOLOGICA 36/2 – 2007 227 vest. In the year 1944 the dolines coverd with fields (field- dolines) reached 7 % (40 counts) that represented 13 % of the total doline-surface. The most common and the greatest were meadow- dolines as they represented 80 % of the dolines (448 counts) and 40 % of the total surface (186,050 m 2 ). Be- cause the surface of a hemisphere is greater than the surface of a circle, meadows were economically more suitable and profited best from the available surface of the doline’s concave structure. Grass can grow on the bot- tom and slope where the soil is thinner and thus gives, theoretically speaking, a greater “output” than it would map 4: Land use in dolines in the years 1944 and 2000 regarding doline preservation. YEAR 1944 YEAR 2000 Land use type in doline Number of dolines Percent (%) Area (m²) Percent of area (%) Number of dolines Percent (%) Area (m²) Percent of area (%) Field 40 7 38,921 13 19 3 6,202 2 Forest 5 1 3,454 1 39 7 42,617 15 Meadow 448 79 186,050 64 230 40 52,965 18 Garden 1 0 669 0 9 2 5,238 2 Sparse trees, overgroving 73 13 59,510 21 41 7 40,215 14 Potencial waste dump 2 0 160 0 74 13 15,046 5 Built up, partly built up 0 0 0 0 154 27 125,146 43 Other 0 0 0 0 3 1 1,337 0 sum 569 100 288,765 100 569 100 288,765 100 Tab. 1: Land use in dolines in the years 1944 and 2000 (regardless the number and area). DEGRADATION Of DOLINES ON LOGAŠKO POLJE (SLOVENIA) ACTA CARSOLOGICA 36/2 – 2007 228 have from the flat and round surface, had the doline been filled up. Therefore the desire to fill up meadow-dolines should be superfluous, but nevertheless their number, in the studied time-interval, was halved (from 448 to 230) and their total surface decreased for 75 % (from 186,050 to 53,000 m 2 ). The mechanization in agriculture had a bigger impact on the diminishing number of meadow- dolines. With the transformation from manual labour to mechanised and more intensive agriculture, dolines became even more unpopular since they represented a relief obstacle to mechanised cultivation. The construction of transport infrastructure in the area of Logatec had a strong impulse on relief changes in the past, particularly because of its geographic location. In the middle of the 19th century the so called “Southern railway line” was constructed through Logatec. Already at that time tracks were placed on filled up dolines that had been thereby lost forever and were even unable to be traced on the photograph from 1944. The burned waste of the railway however is the first known waste material that filled dolines around the Southern railway line. f ur- thermore it is not known how many dolines were filled up with waste material from the railway embankment of the line Logatec – Idrija, close after World War I. Consid- ering these historical facts there had probably been more dolines present in the studied area than were determined by the analysis of the aerial photograph from 1944. Dolines have changed and disappeared also because of settlement-expansion as the area of Logatec has one of the most positive migration saldos in Slovenia. New neighbourhoods are being constructed increasing en- vironmental pressures as more inhabitants cause more waste water, more waste dumps and consequently less dolines. Between 1944 and 2000, 154 dolines were fully or partly built-up representing 43 % of the total doline- surface (125,146 m²). The number would increase greatly if the dolines that were destroyed by the commercial- industrial zone Logatec, which was built after the aerial photograph was taken in the year 2000, were included. Lost dolines that were covered with built surfaces during the last 50 years had been previously filled up with di- verse materials – from excavation material to municipal and other types of waste. Fig. 1: Traditional meadow doline (photo by m. Gabrovec). Fig. 2: The railway embankment of line Logatec – Idrija, closed after World War I (photo by m. Breg). f ILLING-UP DOLINES WITH WASTE MATERIAL On the study area of Logaško polje the degradation proc- esses of dolines have been very intense during the last fifty years. f rom the aspect of nature protection and an environmental point of view it is important to identify the material used for filling up the dolines since these are areas of concentrated water through flow into the karst subterrain. With the increase of municipal waste its percent- age among the filling material rose. Over several decades the illegal waste dumps became a significant anthropo- genic element in the karst landscape. Therefore not only their impact on karst aquifers and ecosystems has to be evaluated, but their influence on changes of surface geo- morphology as well. With the used methodology and the acquired data it is difficult to define the number of waste-filled dolines since it is impossible to get access to the actual structure of the material. The clearest evidence is the abnormal texture identified on the aerial photo- graphs (1944 and 2000) and typically characteristics for waste dumps. With this method, 74 dolines were marked MATEJA BREG ACTA CARSOLOGICA 36/2 – 2007 229 as a potential waste dump, but the greatest methodologi- cal weaknesses are several already overgrown and waste- filled dolines that were not marked as such. The increasing quantity of municipal waste was a suitable material for filling up dolines, especially dur- ing the 70’s and 80’s. A rather new phenomenon is the municipal waste of the recent decades. Regardless its size dumps contain different types of waste, also including domestic rubbish. Waste dumps in dolines were studied in detail by I. Šebenik (1994) in the scope of a research on illegal dumps in Slovenia. The author ascertains that areas with “suitable” locations for illegal dumps have sev- eral characteristics: they are accessible, less visible (phys- ical depressions), covered by vegetation, remote, un- functional and uninhabited. Two thirds of dolines filled with waste are located in the forest or are covered with a bushy-vegetation. Less than 15% of waste-dolines are in the form of meadows or abandoned pastures. Dumps in dolines are most commonly unspecific (these repre- sent 84% of the waste), some are periodical or private. On both larger and smaller dumps mixed waste materials (including waste from households) prevail. A large part is in the form of dug material and tailings as a residue of different activities (e.g. house-construction), which are being transported to illegal dumps together with the rest of the waste. This kind of unusable material is very common in karst areas and in many cases represents the majority of waste materials. 75% of dumps are accessible through roads and only 10% of the waste is dumped be- yond. Dolines are furthermore favourable dump locations due to their steep slopes that make depositing simple. In karst areas it is common to believe that dolines need to be filled up since they are only pointless and limiting holes (Šebenik, 1994). With the handicraft and industrial workshops, new forms of hazardous waste products arrived that were dumped uncontrolled until the introduction of adequate legislation and the set up of regulated dumps. f or the fill-up, different waste materials were used depending on their availability. With the growth of transport (railway), handicraft (blacksmith, charcoal-burning) and indus- trial activities (timber, cardboard-box and metal indus- try), hazardous waste products were produced. Several landfills that are already covered and overgrown contain heterogeneous and dangerous waste (sawdust, bark, in- dustrial oils, galvanic sediment etc.) (Bricelj, 1988), that was deposited thirty years ago or even earlier. With the population growth and production-ac- tivities, built-up surfaces and garbage quantity have in- creased. The municipality of Logatec produces yearly 4,000 tons of waste (SURS, 2005). Until the 90’s the public collecting of municipal waste was gradually introduced in Slovene settlements that until then had to dump their increasing amount of waste somewhere nearby. Later it was taken over by public companies that continued to dispose the waste in dolines. Regarding preliminary studies (Smrekar et al., 2005) active illegal waste dumps contain the highest percentage of construction waste (more than 70 %), while the per- centage of municipal waste is decreasing. Considering these facts in combination with a growing migration and an increased interest for new or better lodging facilities on the Logaško polje the filling up of dolines with con- struction waste will most likely continue in the future. Fig. 3: Waste dump (construction and demolition waste) in the meadow-doline (photo by m. Breg). INTEGRATED ISSUES f OR THE PROTECTION AND PRESERVATION Of DOLINES Based on the presented example of the degradation of dolines on the Logaško polje and by considering the fact that it is a common problem in Slovenia (dumps and landfills in dolines in Slovenia, Šebenik 1994) it becomes obvious that dolines – a typical karst feature – are almost entirely ignored in the existing system of protection and planning of land-use, nature and environment. Dolines on the Logaško polje are the prevailing surface karst land- forms and have in this form always been a strong element of the cultural landscape. The attitude of the population towards this landscape and the consciousness of the im- portance of its particularity have considerably changed with the diminishing role of agricultural activity (in so- ciety and space) and with the consequently diminished DEGRADATION Of DOLINES ON LOGAŠKO POLJE (SLOVENIA) ACTA CARSOLOGICA 36/2 – 2007 230 dependency on natural factors. Secondary and tertiary activities, which are not exclusively based on local capital and natural resources, took the lead. The consequences provoked by non-agricultural activities in the karst land- scape (construction, industry, transport etc.) are more unsustainable and less environmentally friendly than in the case of agricultural activities. In the scope of the existing legislation it is necessary to define the possibilities for a long-term (sustainable) protection of dolines and to propose a new approach in spatial planning for geomorphologically unique doline- areas respectively. Considering the paradigm of sustain- ability the landscape and its landforms, as part of Earth’s surface, would need to be treated as non-renewable natu- ral resources – more precisely as a geomorphologic re- source. Dolines are elements of the natural space which intervene with man’s cultural space forming the unique karst landscape. “ A landform becomes a geomorphological resource only if it has social implications, that is, only if other pa- rameters, external parameters, come into play to invest it with value (Panizza and Piacente, 1993). As long as a particular river, or a particular landscape are studied by and known only to scientists and researchers, it remains “private” knowledge and its potential as a resource do not materialize. However, if the scientist or the researcher publicizes it, making its cultural and environmental sig- nificance known to the general public and thereby giving it a social dimension, then the landform becomes a geo- morphological resource in the eyes of society at large (Pan- izza, p. 22, 2003). ” As a consequence it is necessary that dolines in the area of Slovene classical karst are consid- ered as areas of geomorphological localities in the future planning of land use. In comparison to subterrainean caves which are subject to the Cave Protection Act (Official Journal of the Republic of Slovenia (in further OJ RS), 2/2004), there is no similar act that would determine the protection and activity-management of doline-areas. The Environment Protection Act (OJ RS, 41/2004) foresees an environmen- tal impact assessment prior to any activity affecting the environment. Before the start of such an activity it is nec- essary to conduct an environmental impact assessment, to obtain environmental protection consent from the ministry and to obtain an environmental protection ap- proval (OJ RS, 41/2004, article 50-51). Thereby protected areas and natural values are being considered. Considering the Nature Protection Act (OJ RS, ar- ticle 37, 96/2004) the scientific evaluation measures are: exceptionality, typicalness, complexity, preservation, rare- ness and its importance for science and the ecosystem In case it isn’t recognized as a natural value, a landforms can be incorporated in the framework of a protected environ- ment. This guarantees a certain level of protection as any activity has to be in compliance with the protection ar- rangement of the relevant area. The Environment Protec- tion Act defines further protected areas (national park, regional park and landscape park) and stricter protected areas (strict nature reserve, nature reserve, and natural monument). In 1944 there were 569 dolines present in the stud- ied area while until the 2000 only 51 (8.69 %) have been entirely preserved and 77 (13.5 %) have been almost (partly) preserved. In 46 years 441 dolines vanished re- sulting in the loss of almost 10 dolines per year. In ac- cordance with the gained results from research-work and by considering sustainable and environmentally-friendly development dolines should be put under protection as a distinguishing karst feature and the level of endanger- ment for doline-areas to be determined. This would then represent the basis for future spatial-planning activities. As a unique feature dolines should be furthermore rec- ognized by local inhabitants, as this is the only way to prevent their uncontrolled degradation. 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