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Slovenia has some of the greatest subterranean biodiversity in the world. The aquatic fauna, with its 200 species, is by far the richest, while the terrestrial fauna, with 150 species, is second only to the more southern areas of the Dinaric karst. Five Slovenian cave systems have been listed among the 20 richest cave systems in the world. The Postojna-Planina Cave System, with its 50 aquatic and 35 terrestrial species is by far the most abundant. The Cave Protection Act protects the subterranean environment as a whole. The state of subterranean habitats has been observed to be deteriorating; the decline is especially drastic around Kočevje.


This indicator shows the number of species in subterranean habitats in Slovenia. Only obligate subterranean species, also known as troglobitic species, have been taken into consideration. The figures have been rounded off, as they are constantly on the rise due to advancements in research. The number of species in subterranean waters, i.e. caves, as well as sandy and gravelly alluvia, encompasses approximately 8% of all freshwater fauna in Europe. The share of terrestrial cave fauna cannot be determined.

A considerable predominance of obligate subterranean species over surface immigrants in a subterranean water body also suggests a high level of cleanliness and thereby usefulness of the subterranean water.


Charts

Figure NB04-1: Slovenian subterranean biodiversity compared to the subterranean biodiversity of nearby countries and North America by number of obligate subterranean species – troglobites
Sources: 

Database Subterranean fauna of the wider Dinaric area, Department of Biology, Biotechnical University, University of Ljubljana, 2007.

Show data
Slovenia Croatia Bosnia and Herzegovina Bulgaria Greece USA
aquatic troglobites number of species 200 150 80 80 90 420
terrestrial troglobites number of species 150 270 290 100 115 930
state area 1000 km2 20 56.5 51 111 132.5 9514
Figure NB04-2: Number of troglobitic points in Slovenia (*Note: There is no terrestrial subterranean fauna in the interstitial water of the Ljubljana Plain [Ljubljansko polje])
Sources: 

Sket, Zagmajster, 2004.

Show data
Selected points with the richest subterranean fauna in Slovenia Postojna-Planina Cave System Logarček Cave Šica-Krka System Križna jama cave Ljubljana Plain
troglobitic species number of species 85 44 38 44 28
Figure NB04-3: Selected points with the richest subterranean fauna in Slovenia, evaluated according to the provisional scoring system by the Department of Biology at the Biotechnical Faculty at the University of Ljubljana
Sources: 

Sket, Zagmajster, 2004.

Show data
Selected points with the richest subterranean fauna in Slovenia Postojna-Planina Cave System Logarček Cave Šica-Krka System Križna jama cave Ljubljana Plain
points due to troglobitic fauna points 1655 720 580 430 420
points for other biological aspects points 19 3 15 3 5
other points 30 5 5 20 15
total points points 1704 728 600 453 440
Figure NB04-4: Density of exclusively cave-dwelling beetles in Slovenia and in its surroundings. (Calculated for the number of species per 400 km2 squares.)
Sources: 

map prepared by: M. Zagmajster; basis: Database Subterranean fauna of the wider Dinaric area, Department of Biology, Biotechnical University, University of Ljubljana.


Goals

·         To preserve a high level of biodiversity and to halt the decline in biodiversity by 2010;

·         to preserve or to achieve a favourable state of species and habitat types that are endangered or located in areas designated as important for the preservation of biodiversity (for example the Ramsar localities).


Slovenia has an exceptional number of obligate subterranean species. It seems that aquatic fauna, with 200 species, is by far the richest, while terrestrial fauna, with 150 species, is second only to more southern parts of the Dinaric karst. Roughly 55% of aquatic fauna is comprised of tiny crustaceans, while 25% are small snails. Over 50% of terrestrial species are beetles. The highest density of species is found in the Dinaric karst of southern Slovenia and other karst areas, while some aquatic fauna is also found in groundwater in non-karst lowlands.

The number of obligate subterranean species in individual cave systems is also high. As many as five Slovenian cave systems have been listed among the 20 richest cave systems in the world. The Postojna-Planina cave system, with its 50 water and 35 terrestrial species is by far the most abundant. Another advantage of this system is the plethora of "young" surface immigrants in the underground river and entrance passages. Species that are progressively better adjusted to the subterranean world as we move along the underground river are of special interest. Apart from caves, a very high number of species are also found in the water of the gravelly lowlands of the Ljubljana Plain (Ljubljansko polje).

Most subterranean animals are not threatened by collectors (scientists or merchants). They are, however, all threatened by pollution, which normally originates from the surface. Many substances pose a direct threat to the underground life. The input of seemingly less dangerous organic substances into the underground enables the invasion of surface species, which are driving out obligate subterranean species. Water in the underground purifies itself only to the level of nitrates, which then accumulate. For this reason, the proteus and subterranean beetles require and are given special protection by the Decree on protected wild animal species (Official Gazette of the Republic of Slovenia, Nos. 46/2004, 109/2004, 84/2005, 115/2007 and 32/08-decCC). This decree also protects the habitats of other subterranean species, i.e. the subterranean environment as a whole. Apart from that, a substantial part of especially biodiverse areas is partly under Natura 2000 protection, while only the rather modest subterranean fauna of the Škocjan Caves is under special protection (as a Ramsar wetland).

The state of waters in sandy and gravelly deposits below the plains is deteriorating; there are also fewer and fewer usable wells where monitoring the conditions is still simple. The state of these deposits has deteriorated significantly in certain places in karst areas as well. The invasion of surface species along the underground river was observed in the Postojna-Planina cave system in the post-war period, but after remediation, the situation has improved. The state of deposits in the Kočevje area is extremely bad. Some subterranean waters are polluted due to intensive livestock breeding and others, due to landfills; the once exceptionally dense proteus colonies have since disappeared. Similar phenomena can be observed elsewhere, though to a smaller extent; animals previously present in caves that are not particularly polluted often cannot be found anymore. There is no systematic monitoring of these changes.

The vast majority of obligate subterranean species are endemic. This means they are only limited to a certain place or area. They are mostly limited to the southern half of Slovenia and many of them to a much narrower area. In addition, their general habitats are broken up into many small patches, making all of these species threatened.


The Department of Biology at the Biotechnical Faculty of the University of Ljubljana collects detailed data on the abundance of species in subterranean habitats for all areas of the former Yugoslavia in the database Subterranean fauna of the wider Dinaric area. The register includes published and yet unpublished data. Data beyond this area are collected and published only for a smaller number of countries, while data for areas with the same surface (which are thus comparable) are still being prepared. The numbers for Bulgaria and the US have been derived from the publications by their local researchers.

With a view to nature protection, the Department of Biology at the Biotechnical Faculty at the University of Ljubljana has created a scoring system for the evaluation of objects. The numbers of obligate subterranean species – troglobites, as well as their endemism, typical localities, etc., are taken into consideration. Points are added for non-troglobitic fauna and other ecological aspects, such as bat colonies, the underground stream fauna, habitat diversity, etc. Points are also added for non-biological aspects: cultural-historical significance, aesthetic values, education, economy (tourism, drinking water) and other aspects.

- Sket, B., 1972. Zaščita podzemeljske favne se ujema z življenskimi interesi prebivalstva [Subterranean fauna protection matches the main interests if the population]. In: Zelena knjiga [Green book], Natural History Association of Slovenia, Ljubljana 137-140, 164-165
- Sket B., 1979. Jamska favna Notranjskega trikotnika (Cerknica - Postojna - Planina), njena ogroženost in naravovarstveni pomen [Cave fauna of the Notranjska triangle (Cerknica – Postojna – Planina), its endangerment and significance for nature conservation]. Varstvo narave [Nature Conservation], Ljubljana, 12: 45-59
- Sket B., 1992. Rdeči seznam ogroženih živali podzemeljskih voda v Sloveniji [Red list of endangered subterranean water fauna in Slovenia]. Varstvo narave [Nature Conservation] 17: 193-204
- Bole J., Drovenik B., Mršić N., & Sket B., 1993. Endemic animals in hypogean habitats in Slovenia. Naše Jame - Our Caves, 35(1): 43-55
- Sket B., 1996. Biotic diversity of hypogean habitats in Slovenia and its cultural importance. Biodiversity - Intern. Biodiversity Seminar, UNESCO, Gozd Martuljek, Proceedings: 59-74
- Sket B., 1997. Biotic diversity of the Dinaric karst, particularly in Slovenia: history of its richness, destruction, and protection. Conserv. Prot. Biota of Karst, Karst Water Inst., Spec. Publ. 3: 84-98
- Culver D.C. & Sket B., 2000. Hotspots of subterranean biodiversity in caves and wells. Journal of Cave and Karst Studies 62(1): 11-17
- Sket B., 2004. Postojna-Planina Cave System: biospeleology. In: Gunn J. ed., Encyclopedia of Cave and Karst Science, Fitzroy Dearborn, New York London, pp. 603-604.
- Sket, B., K. Paragamian, and P. Trontelj, 2004. A census of the obligate subterranean fauna in the Balkan Peninsula. In: H.I. Griffiths & B. Krystufek (eds), Balkan Biodiversity. Pattern and Process in Europe's Biodiversity Hotspot. Kluwer Academic Publishers B.V., pp 309-322.
- Sket, B., Zagmajster, M., 2004. How to inventory and evaluate the biologically important subterranean world heritage? The case of Slovenia.(abstract). Acta carsologica 33(2, suppl. 1): 28.
- Sket B. (2005) Subterranean animals in Slovenia: protecting habitats, not specimens. New currents in conserving freshwater systems (Ed J. Stenzel), p. 22. American Museum of Natural History-Center for Biodiversity and Conservation, New York.


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