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Classical Karst (in Slovene language: Klasicni kras)

Date of Submission: 25/11/2015
Criteria: (vii)(viii)(ix)(x)
Category: Natural
Submitted by:
Permanent Delegation of Slovenia to UNESCO
Coordinates: N45 40 E13 54
Ref.: 6072

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The Classical Karst is part of the Dinaric Karst. Dinaric Karst is a typical karst landscape located in temperate latitudes, the largest continuous karst surface in Europe and belonging among the largest karst surfaces in the world. The karst landscape is the most widespread landscape type in Slovenia. Classical Karst covers the area between the Ljubljana Marsh (Ljubljansko barje) and the Bay of Trieste. There are around 6,000 known and explored caves in this area that cover approximately 6,400 km2 or 27% of the territory of Slovenia. The geological strata of the Classical Karst comprise Triassic, Jurassic and Cretaceous limestone and dolomites, as well as Palaeocene and Eocene limestone to a lesser extent. The bottoms of poljes are backfilled by Quaternary alluvium from rivers and streams. The geomorphology of the Classical Karst strongly reflects the tectonic processes. The area of the Classical Karst has an extremely diverse relief. The higher relief in the central area comprises high karst plateaus that drop off in cascades into lower-lying karst plateaus or poljes. Rivers that spring from non-carbonate rocks disappear at the contact with the karst landscape and form blind valleys or cross the karst via karst valleys and gorges. Numerous extensive and complex cave systems were formed by the disappearing streams and are connected to the surface by numerous shafts. Fluvio-karstic phenomena such as dry valleys are frequent on the dolostone basement. Karst rivers appear only at the bottom of poljes.

The karst region of Slovenia is among the richest areas in Europe in terms of flora and fauna and one of the global "hotspots" of biodiversity. There are some typical archaeological deposits of plant and animal species; this was where the first troglobitic cave-dwelling animal species were discovered and scientifically described.

The image and use of the man-made environment is also closely linked to the rock composition of the karst landscape, as is the karst architecture. The man-made environment is adapted to the use of limestone as the basic building material, as well as to the shortage of arable land. The oldest known traces of human inhabitation of the Classical Karst come from the karst caves of the Palaeolithic.

Cave tourism began developing in the Classical Karst as early as in the 17th century. Vilenica is mentioned as the oldest tourist cave (since 1633), while cave tourism began developing more intensively in the 19th century when the Postojna Cave (Postojnska jama) and the Skocjan Caves (Skocjanske jame) were discovered.

The Classical Karst is extremely important for the history of research of the karst and karst phenomena, i.e. the development of karstology and speleology. The first records go back to antiquity, while continuous and true scientific research began at the end of the 16th century. Today, the Karst Research Institute (lnstitut za raziskovanje krasa) of the Research Centre of the Slovenian Academy of Arts and Sciences based in Postojna holds the leading research role. The areas of the Classical Karst with outstanding universal value are: the Kras (Kras), the Podgrad lowland (Podrgrajsko podolje), the Postojna Karst (Postojnski kras) and the Poljes of the Classical Karst with the Rakov Skocjan valley (Kraska polja z Rakovim Skocjanom).

1. Kras (Kras)

Kras is a carbonate plateau with elevations from 250 to 600 metres that lies between the Gulf of Trieste in the west and the Friuli lowland in the north-west; it is limited by flysch rocks in the Vipava Valley in the north and by the Reka Valley and Brkini in the south-east. The Karst Plateau is approximately 60 km long and 15 to 20 km wide, covering an area of around 800 km2, 440 km2 of which lie in Slovenia and the remainder in Italy. The plateau surface is rocky and features no surface-running water. The Kras is formed of two fold structures made of Cretaceous and Palaeogene carbonate rocks created by the subduction of lstria under the Kras. Numerous and diverse surface and underground geomorphological karst features are represented in the Kras. The most frequent relief feature is the doline. There are up to 100 dolines per km2 and they cover nearly 10% of the entire area of the Kras. Other characteristic relief features include large blind valleys, dry valleys and large collapse dolines primarily above the groundwater flow of the Reka River. The rocks exposed on the surface also exhibit various small macro and micro solution features. Another important geomorphological element is the denuded caves that were destroyed by denudation to such an extent that only cave sediments and cave passages without roofs have been preserved on the present surface and that are the oldest karst elements in the landscape.

More than 1,500 speleological formations have been discovered in the Kras to date with an average density of 2 caves per square kilometre and in places as many as 40 caves per square kilometre. The longest cave complex is that of the Skocjan Caves (Skocjanske jame) and Kacna Cave (Kacna jama) (together, they are more than 20 km long) with the deepest caves reaching down to 330 m. These are shafts that lead to the underground Reka River, which has formed an exceptional underground hydrological network in its groundwater flow. The Reka River is the largest Slovenian sinking stream with its groundwater flow beginning at the ponor in the Skocjan Caves, after which it runs below ground for 35 km to the sources at Stivan. The typical torrential character of the Reka River is exhibited in the rapid change in the water table in the caves, which can rise by 100 metres or more in a very short time. In addition to the hydrologically active caves, there are many relict caves that were formed by underground streams. Cave sediments were deposited there, especially flowstone material that is present in various forms and colours. Fossil remains have also been preserved in the cave sediment. In addition to the speleological formations, another important relief form is the denuded caves, i.e. remnants of caves that were uncovered by denudation. The fauna found in the Karst caves is diverse. Fossil remains of the species Marifugia cavatica have been found in a denuded cave that have been dated at more than 4 million years old, which makes them the oldest known remains of a cave-dwelling animal and in turn testifies to the long and continuous development of this karst.

The Kras is the area where the first systematic research of karst phenomena in the world began at the start of the 20th century. This was the start of continuous organised speleological exploration that is still going on today. The Kras Plateau played the pioneering role in the naming of karst phenomena and this is why the landscape was termed Kras.

2. Podgrad Lowland (Podgrajsko podolje)

Podgrad lowland (also called Materija lowland -Matarsko podolje) is a 20 km long and 2 to 5 km wide continuation of the Kras Plateau, with its northern edge representing the area of contact karst between the carbonate Kras Plateau and the flysch hills of Brkini. lt rises 490 m above sea level in the north-west and up to 650 m on the south-eastern side. There are 17 sinking streams that disappear along its edge and have created a well-formed series of blind valleys, including Odolina, Jezerina and Raciska Dana. Blind valleys are an exceptional example of the interaction of surface and underground karst drainage reflected in the formation of the relief on carbonate and non-carbonate rocks. The territory rose tectonically during the formation of the abovementioned valleys.

3. Postojna Karst (Postojnski kras)

The Postojna Karst comprises three individual units: a) the surface between the Pivka Basin (Pivska kotlina) and the Planina polje (Pianinsko polje) with the Postojna Cave and Planina Cave (Pianinska jama) as a part of the broader Postojna-Pianina cave system, b) the Predjama cave system, and c) the Pivka intermittent lakes with the surface flow of the Pivka River. The characteristic relief of the karst planation with hills and numerous dolines and collapse dolines has developed at a height above sea level of 550 to 700 m. The area of Cretaceous, Jurassic and Triassic limestones and dolomites ends in the south-west with Eocene limestone where contact karst features appear. Numerous surface and underground karst phenomena have developed on the limestone, with dolines, collapse dolines and caves being a predominant feature. Dolines cover almost the entire area and have a density of 300 dolines per km2.

The Postojna Cave is a complex of cave passages that are more than 20.5 km long, lie on several levels and feature multiple historic entrances (Postojna Cave, Pivka Cave, the Otoska jama Cave, the Crna jama Cave and the Magdalena Cave). The upper levels are dry and feature river sediment and rich speleothem formations. The lower passages have water as the Pivka River runs through them and inundates them. The explored cave passages end in a siphon, while the perennially water-filled cave passages continue into the 6.6 km long Planina Cave (Planinska jama) with the subterranean confluence of the rivers Pivka and Rak. The Postojna Cave is exceptional on account of the great length of the large wet and dry passages, large halls, collapse dolines above wet passages, as well as in terms of the history of visits and exploration. The following cave-dwelling species were first found and scientifically described in the Postojna Cave in the 19th century: the Leptodirus hochenwartii beetle, Zospeum spelaeum snails, Neobisium spelaeum pseudoscorpions, Stalita taenaria spiders, and latter also cnidarians (Velkovrhia enigmatica), etc. The Postojna Cave and the Planina Cave are type localities (locus typicus) for around 90 species of invertebrates. With more than one hundred currently known aquatic and terrestrial troglobitic species and a large number of troglophile and trogloxene aquatic and terrestrial species, the Postojna-Pianina cave system is one of the richest cave systems in terms of fauna. Troglobite populations of eutroglophile species are especially interesting from the scientific point of view, such as AselIus aquaticus and others.

The Predjama cave system was formed by the Lokva Stream, which disappears beneath a 120 m tall overhanging rock face at the end of a deep blind valley. The rock face has several entrances on several levels that lead into a 13.1 km long Cave under Predjama Castle (Jama pod Predjamskim gradom). Archaeological remains have been preserved in some passages that show the use of the cave from the Eneolithic to the Middle Ages. The picturesque Predjama Castle was built in the rock face that is functionally connected to the cave passages and was first mentioned as early as 1202.

Pivka intermittent lakes with the Pivka River were created in a former polje, the hydrological characteristics of which were changed by neotectonic displacement. During high water stages, the Pivka River, which is part of the basin of the karstic river Ljubljanica, runs on the surface, while during low water stages it disappears underground beneath the Javorniki hills and runs directly towards the Planina polje. During extensive precipitation, the water stage of the karstic water rises and fills the bottoms of depressions, creating short-term lakes. More than 15 of these lakes are known. The seasonal occurrence of a massive population of the Chirocephalus croaticus fairy shrimp is especially interesting.

The Postojna Karst has played an important role in the development of speleology and karstology. The role of the Postojna Cave is especially important. The first visits to the Postojna Cave were recorded in 1213. After the discovery of the interior sections of the Postojna Cave in 1818, the interest in karst and cave exploration increased significantly. The development of speleobiology began after the surprising discovery of the blind Leptodirus hochenwartii beetle in 1832 and the transition from random finds to active exploration. The arrangement of the Postojna Cave for tourism purposes represented an important promotion of the entire Classical Karst.

4. Poljes of the Classical Karst and the Rakov Skocjan Valley (Kraska polja in Rakov Skocjan)

There are numerous poljes in the Classical Karst, which are representatives of karst formations in various stages of geological development. All poljes are polygenic and polyphase. In the central (highest) part of the Classical Karst, a narrow belt of a lower relief was created along the ldrija fault zone where the poljes are located in a series and are in contact with the karst water table. The most representative poljes are the Cerknica polje (Cerknisko polje) and the Planina polje, while a special feature is the Pivka intermittent lakes, which represent a polje in the final development stage.

The development of closed karst depressions such as poljes is the result of tectonics and accelerated corrosion that was influenced by the geological structures and the specific hydrological networks. This is especially reflected in long-lasting seasonal flooding and other karst water phenomena such as springs, ponors, estavels, sinkholes, active caves, and occasional and perennial surface-running flow. The caves found in poljes are active/wet caves (lowest-lying ones), intermittently active caves and completely inactive caves. All the water elements of the poljes of the ldrija fault zone in the area under consideration are part of the hydrological network of the karst Ljubljanica.

Poljes are rich in vegetation that is characteristic of this environment and adapted to different water stages (floods and droughts). Planina polje is an overflow polje that is 6 km long and 2 km wide. The depression is 50 m deep and encompasses 16 km2 of the flat surface with a height above sea level of 450 m. On the south-western side, it has two narrow pocket valleys and represents the most important confluence of the groundwaters in the river basin of the Ljubljanica River. Floods begin during high water stages in the karst and last up to several months per year. There were attempts at regulating the regular floods on the Planina polje as early as in the first half of the 191h century. The so-called Putick's wells (deepened and walled-in sinkholes in the form of wells) from the period prior to the First World War have been preserved. In the north-westernmost part of the floodplain meadows is the habitat of the Amethyst Meadow Squill (Scilla litardierel), which is endemic to the Dinaric poljes; the wild gladiolus (Gladiolus illyricus) and various other less noteworthy plants also grow here.

The Cerknica polje (Cerknisko polje) is a typical polje with the largest and most characteristic intermittent lake in Slovenia. This is where the cave salamander was found that was the basis for its scientific name Proteus anguinus Laurenti (1768). lt is often called the Cerknica intermittent lake because of the regular flooding. The bottom is flooded for a few months each year, namely in the fall, winter and spring. The area of the bottom of the Cerknica polje is 38 km2 and lies at a height above sea level of around 550 m. When the intermittent lake is full, it encompasses 26 km2 and is 10.5 km long and 5 km wide. Most of the karst hydrological phenomena have developed here. The water runs off from the ponors directly into the springs of the Ljubljanica River or towards Rakov Skocjan. The Krizna Cave (Krizna jama) lies in the catchment area of Cerknica lake, which is known for flowstone dams that form a total of 47 lakes, numerous fossilised remains of the cave bear (Ursus spelaeus) and great biodiversity. The unusual hydrological characteristics of the Cerknica polje piqued the interest of experts as early as in the 161h century, while the lake became well-known from Valvasor's descriptions from 1689. Numerous plans for the exploitation of the lake have been drawn up in the past. The first plans for draining the lake were mentioned by Hacquet in 1778, while plans were later produced for building a dam and creating a permanent lake. Several smaller land reclamation efforts were made, as well as other interventions, but the lake nevertheless remains in a relatively natural state.

Rakov Skocjan is a roughly 1.5 km long and 200 m wide pocket valley. lt was created on Cretaceous limestones and features a thin layer of river sediments at the bottom. lt lies between the Planina and Cerknica poljes at a height above sea level of around 500 m. The permanent flow of the Rak River runs through the valley and springs from the Zelske jame caves. The Zelske ame caves are approximately 5 km long and terminate under the Velika Sujica collapse doline, at the bottom of which the Karlovice cave system terminates on the other side. The Karlovice cave system is the main subterranean outflow of the Cerknica polje. In the surroundings of the entrance to the Zelske jame caves, there are numerous collapse do lines, one of which features a preserved 60 m tall Small Natural Bridge (Mali naravni most) over the collapse doline. Downstream, the valley widens and numerous springs feed the Rak River. The valley narrows at the Large Natural Bridge (Veliki naravni most), and the Rak River disappears into the Tkalca jama Cave, from which water runs into the Planina Cave where the subterranean confluence of the rivers Rak and Pivka is located. The Rakov Skocjan valley was created by the collapse of a large cave system that was located just beneath the surface. Only the outlet and inlet caves, which are connected by the Rak River on the surface depending on the karstic water table, remain of the said system.

Justification of Outstanding Universal Value

Classical Karst is a distinct karst landscape with distinct karst phenomena where exceptional “karst" natural phenomena have been described since antiquity. The Kras Plateau got its name from the domestic name for the rocky, poorly-fertile landscape; i.e. kras (karst in English). Its German name "karst" was therefore accepted as the scientific name for a special type of landscape that developed in carbonate rock. This area also gave names to a set of professional terms for numerous karst phenomena such as doline and polje. The terms karst, karstic and karstology have become part of the national scientific vocabulary. Classical Karst unites a geographically rounded off area of carbonate rock, the globally most recognisable type of karst, lying in temperate latitudes of a wet climatic zone with preserved characteristics of natural phenomena, which represents an outstanding universal value. The typical characteristics of natural phenomena, their genesis and the multi-century history of the research of the karst and karst phenomena have introduced the karst terminology into scientific nomenclature.

The exceptional features of the Classical Karst, which is part of the Dinaric Karst, lies in the connection and combination of lithology and geological structure. The diverse combinations of thrust units from carbonate and poorly permeable rock have created hydrogeological barriers and conditions for the occurrence of poljes. The intertwinement of the surface and underground action of water and the associated chemical processes have enabled deep karstification. The exceptional nature of karst caves is exhibited in the variety (on a global scale) that results from the different types (inactive caves, active caves, cave complexes, shafts, spring caves, etc.) and dimensions (the longest cave systems are more than 20 km long), as well as the sheer number of speleological formations per unit of surface area -around 40 entrances/km2 in the area of Sezana.

The variety is also exhibited by the quantity of cave passages with flowstone formations, types of flowstone and its forms (stalactites, stalagmites, curtains, cave pearls, etc.). The importance of cave sediments for scientific research should also be specifically highlighted. Based on the carbon dating of the said sediments, the age of the caves was determined and the dynamics of the development of the karst scientifically explained. The oldest scientifically dated flowstone is between 3 and 4 million years old and comes from several locations in the Podgrad lowland and above the groundwater flow of the Reka River. The series of blind valleys in the Podgrad lowland is a unique and best preserved example of such geological formations in the karst on the global scale.

All the surface and subterranean karst features of the moderate climate zone have developed in the Classical Karst, including macro and mezzo (poljes, uvalas, collapse dolines, dolines, dry valleys, blind and pocket valleys, ponors, karst springs, estavels and caves), as well as micro (rillenkarren, karren and solution pans).

The uniqueness of Classical Karst is also multifaceted in speleobiological terms. The first troglobitic species (Laurenti, Schmidt) were discovered in the Classical Karst; the first speleobiological monograph (Schioedte, 1849) was written about the caves in the Classical Karst; based on this, the first eco classifications of subterranean fauna were designed. The relative density of troglobitic species (within the scope of the broader Dinaric area) is also highest here in global terms, and the exceptional density of the Coleoptera or beetles is up to 20 species per 20 km2, making it the richest cave system in terms of fauna with over 100 troglobitic species. The rate of endemism is also extraordinary (close to 100% of the species and around 50% of genii are endemic to at least the Dinaric area, while a large share is also endemic to Slovenia. The conditions in the Classical Karst have provided excellent opportunities for evolutionary research and insight into the creation of subterranean fauna.

Criterion (vii): Ever since antiquity, numerous explorers and experts have depicted this dramatic landscape with caves, water bodies and poljes. Karst features and phenomena are preserved in their natural state, as is the landscape as a whole. The aesthetic value of this area has been formed through centuries of co-habitation and dependence between man and nature. The Classical Karst represents an example of a typical karst landscape where the shortage of arable land and water has prevented the intensive use of space. The global recognition of the Classical Karst was strongly affected by the development of cave tourism that builds on the extraordinary natural beauty and aesthetic value of karst caves.

Criterion (viii): The geological development of Classical Karst is closely tied to the dynamic events on the carbonate platform and the intense tectonic processes that have affected the development of the surface. Recent research even shows that particular types of karst geomorphology are tied to particular types of tectonics. Classical Karst represents an area of pioneering tectomorphogenic-speleogenic karstological and historical research. The Karst features special and typical hydrological conditions -underground runoff and corresponding special hydrological phenomena. These phenomena are highly diverse in the Classical Karst and include karst springs, great and deep vaucluse springs. One of the exceptional springs is the Gabranca Spring near Neverke (water rises more than 200 m). Hydrological phenomena also include estavels and various types of ponors, ranging from alluvial to large inlet caves such as the more than 20 km long Postojna Cave. Groundwater connections between disappearing streams and the nearby poljes are especially interesting. The connections are frequently very complex and take the form of networks, including surface and underground bifurcations where water runs off to different springs during different water stages. The distances between ponors and springs can be very long such as the one between the Skocjan Caves (Skocjanske jame) and the springs of the Timavo which is around 35 km. Poljes are a special phenomenon from the hydrogeological point of view as well. The Cerknica polje is an intermittently flooded polje -an intermittent lake -and represents and includes karst features and phenomena characteristics of poljes and karst depressions, as well as all the characteristics of the karst relief. lt is also important historically as it has been mentioned by authors since antiquity with the first printed accounts going back to 1537. Around 6,000 caves have been explored in the Classical Karst. A high share of cave systems confirms that the karst processes have developed in all directions. Some caves have an outstanding aesthetic value considering the extensively branched cave passages and the variety of the speleothem inventory. An important relief feature of the Classical Karst is the blind valleys that occur at the contact of the surface non-karst and karst river networks. The formation of the relief at ponors reflects the situations in the karst at the time of the development of features and serves as a diagnostic relief feature. The series of blind valleys in Brkini is among the best examples of this karst phenomena.

Criterion (ix): The long-term development of Classical Karst without any interruptions is also reflected in its rich subterranean fauna. Biological research of the underground world, i.e. speleobiology, began in this area and this is when numerous animals were first described. This is where the type localities of the first known cave-dwelling animals, the cave salamander (Proteus anguinus Laurenti) (1768) and the beetle Leptodirus hochenwartii Schmidt (1831) are located. The Postojna-Pianina cave system is also the richest cave system in the world with more than 1 00 troglobitic species. Quite a few Pleistocene animals (cave bear, cave lion, hyena and others) have been preserved in caves. Caves also serve as an important occasional dwelling or refuge for larger forest animals such as dormice, bats, badgers, foxes and bears. The history of the deforestation and reforestation of the Karst with the accompanying opening of new habitats is especially interesting and instructive.

Criterion (x): Caves and extensive systems of fissures in karstified rock serve as a habitat for a diverse troglobitic fauna. These animals are able to feed on the elements of the relatively extensive bioproduction on the surface, which enter the underground along with the relatively large quantities of infiltrating water. Various habitat types are present in the Classical Karst: surface, intermittently flooded and aquatic habitats, as well as intermediate habitats (underground-surface). Intermediate habitats are also settled by certain troglobitic and troglophile species. Certain sessile (and mostly filter feeding) troglobitic animals such as cnidarians (Velkovrhia enigmatica), the Marifugia cavatica tube worm and Congeria kusceri. The first troglobites from the Classical Karst to be described were: the cave salamander (Proteus anguinus) from Cerknica Lake; the beetle Leptodirus hochenwartii from the Postojna Cave and a whole range of others. The surface fauna is rich here. Its special members include large forest mammals, including large predators, wetland birds, vertebrates in rocky habitats and invertebrates from aquatic and surface semi-subterranean "cryptic" habitats (springs, soil).

Forest fauna includes the brown bear, wolf, jackal and the re-introduced lynx.

The variety of flora in the karst is first and foremost dependent on the interaction between the climatic, edaphic, hydrological and orographic conditions throughout geological history. An important factor that contributes to the high level of fauna diversity in the Classical Karst is also the relatively small human impact owing to the low density of settlement and land use type that includes pastoralism and the exploitation of forests. On the other hand, the karst was also the hub for numerous groups of plants before, during and after the ice ages. The Western Balkans were one of the flora refuges during glaciation. All of these factors -independently or jointly -have shaped the especially extensive diversity of karst flora and vegetation. Even though many original landscapes have experienced different levels of ecosystem disruption, the exceptional local and regional diversity of vegetation and flora has been preserved. lt is the Mediterranean and sub-Mediterranean mountains especially that are home to habitats for Tertiary, glacial and post-glacial relict species. Through deforestation in prehistoric times, humans have even contributed to the diversification of the flora by opening up space for the occurrence or expansion of habitats that are today perceived as natural (dry meadows, rock flora).

Statements of authenticity and/or integrity

Select areas of the Classical Karst include all the karst phenomena typical of karst in moderate latitudes, including plant and animal species and their habitats, and they also represent a complex intertwined area suitable for the presentation of these phenomena, species and habitats. lt is especially important that some karst phenomena, processes and animal species were first recognised, described and professionally proven in the Classical Karst. The knowledge of these contributes significantly to the understanding that natural processes are a universal value of the Classical Karst and the karst landscape in general.

The karst phenomena of this area that were formed by specific natural processes, lithology and tectonics are developed in both the surface and underground relief features. A long, continuous development of karst geomorphological features (more than 20 million years) has also enabled the development of varied and exceptional cave fauna. Each selected area represents one or several complete karst systems with all the micro and macro features; e.g. a system of speleological formations with the underground flow of the Reka River, a system of blind valleys with disappearing streams and typical poljes in various stages of development. Surface and underground karst phenomena in select areas are well-preserved.

Cave passages and cave the inventory of the underground flow of the Reka River and the caves above it are well-preserved. There are small settlements, infrastructure and extensive land use present on the surface, but they do not represent a great risk for the pollution of the water, caves and the cave inventory. Some of the best preserved caves that need mentioning is the Gustinciceva jama cave in the Blazceva dolina valley and the Nova Krizna jama cave (Jama v Grdem dolu), which are closed to the public due to their exceptional nature and the state of preservation of the cave features, whereby access is only allowed with the permission of the competent ministry.

The series of blind valleys in Brkini with disappearing streams are well-preserved. Only extensive farming is pursued in the bottom of blind valleys and their catchment so there is no extensive risk for the preservation of the natural condition.

The Postojna Cave and Planina Cave, together with the other cave complexes, represent an important habitat for troglobitic species. The good level of preservation of the habitats and their rate of occurrence is reflected among other things in the numerous endemic species and the fact that the Postojna-Pianina cave system is one of the hotspots in terms of the number of species. The area is well-preserved despite the fact that the Postojna Cave is visited by more than half a million visitors each year, and the fauna there does not seem to be under threat. In historic terms and on account of the changes to the natural environment, the Postojna Cave is also considered an especially instructive example of the development of the karst, humans in the karst, the economy and finally the science (changes to the natural environment must be presented as serving the function of development).

Poljes are well-preserved; they are only partly cultivated, which is true of the areas of the Pivka intermittent lakes as well. Traditional sustainable agricultural use over the centuries has proven to be an important factor in the preservation of habitats and biodiversity.

Comparison with other similar properties

Karst landscapes cover approximately 11% of the Earth's surface. Classical Karst is a component part of the Dinaric Karst, with the Skocjan Caves in Slovenia, Durmitor in Montenegro and the Plitivice Lakes in Croatia already being inscribed in the World Heritage List. All these areas are inscribed as independent properties. Classical Karst is a rounded off whole of all the typical karst phenomena and processes, and is also a biotic hotspot. The added value of the Classical Karst that sets it apart from other karst areas around the world is the longstanding and continuous history of research -systematic and speleological research, as well as scientific research and the development of karst terminology. The Karst landscape has yielded the Slovenian and internationally recognised German scientific term "karst" and the toponym for a karst feature -"doline". Exceptional geomorphological phenomena that we now call karst phenomena have been described in the Classical Karst since antiquity. The Karst is the cradle of the new science of karstology.