UNESCO wORLD KARST NATURAL HERITAGE SITES: GEOGRAPHICAL AND GEOLOGICAL REVIEw

. The paper is devoted to the review of the World Karst Natural Heritage and the perspectives of such new properties in the Russia. Presently there are 37 World Karst Natural Heritage sites on the globe; 34 of them have the natural heritage and 3 sites have the mixed, natural-cultural significance. The World Karst Heritage distribution by the countries and by parts of the world was analyzed. A brief description of outstanding universal value of the “Lena Pillars Nature Park”, being currently the only Russian karst area nominated at the List of World Natural Heritage by a specific type of the karst – ground frozen karst, was given. The necessity of the new World Karst Heritage properties characterizing by the karst development in sulfate and salt rock sites are considered. The karst areas, located in extreme (cold or arid) climate conditions, are in the focus of separate attention.


INTRODUCTION AND BACKGROUND
The identification, protection and preservation of natural and cultural heritage having the outstanding universal significance for the humanity are the one of the United Nations Educational, Scientific and Cultural Organization (UNESCO) objectives. This idea was the basis for the international «Convention for the protection of the world cultural and natural heritage» signed in 1972. Cultural heritage includes «monuments, groups of buildings and sites with historical, aesthetic, archaeological, scientific, ethnological and anthropological value» (World Heritage… 2005); and "outstanding physical, biological and geological formations, habitats of threatened species of animals and areas with scientific, conservation or aesthetic value" (World Heritage… 2005) are referred to the natural heritage.
Currently the Convention has been joined by more than 190 countries, and the World Heritage Fund, operating under the auspices of the Convention, assists to States parties in the World Heritage Sites identification, protection and development.
The aim of this paper is to present the review of the World Karst Natural Heritage and the conditions in which the unique outstanding karst is developed as well as to indicate the perspectives and necessity of the new Russian karst nominations preparation.

THE wORLD KARST HERITAGE DISTRIBUTION ON THE GLOBE
Among the natural sites, inscribed on the World Heritage List and having the high natural or natural-cultural (mixed) status (in total 241 sites as of January 1, 2018), a special group is formed by the 37 karst properties (Fig. 1, Table 1) (Gunn 2004;Williams 2008;Trofimova and Hada 2016;etc.). Such large number of karst properties described by the universal significance is defined by a wide spread of karstic rocks (limestone, dolomite, etc.): nearly 30 % of continental surface is characterized by the conditions of karst development.
Thirty-four World Karst Heritage sites are distinguished by their natural properties. The picturesque canyons, profound karstholes ( Fig. 2), blue-eyed karst springs as well as the enormous underground systems are preserved here. Three karst properties are determined by a mixed (natural and cultural) status: the temples, monuments, etc. referring to the different stages of contemporary civilization development and coupled with the caves where the priceless archaeological and paleontological material was found.
Nahanni National Park (Canada) (18, here and in the rest of the text the number (X) in ENVIRONMENT parentheses correspond to that represented in Table 1 and shown on Fig. 1) is the first karst natural object inscribed on the UNESCO List in 1978.
As can be seen from Table 1 and Fig. 1, the largest number of the World Heritage Sites is situated in the China -five natural areas nominated: (1-5). All of them belong to the areas of karst development in the central and southern parts of the region researched. According to M.M. Sweeting (Sweeting 1995), the karst occupies more than 15% of the China territory, that is the reason that the numerous works of the Institute of Karst Geology (Guilin, Guangxi) are devoted to the karst processes study. In December 2008 this Institute was renamed to the International Research Center on Karst under the Auspices of UNESCO where the substantial attention is focused on the exploration of karst manifestations universal significance.
Four unique karst objects are located in the Australia: (6-9), therewith the World Heritage Site "Australian Fossil Mammal Sites (Riversleigh, Naracoorte)" (8) consists in two parts, the northern and southern, united in the one nomination. Since the end of last century the Australian colleagues have paid much attention to the protection of karst areas, in particular to the ones having the property of the World Heritage (Middleton 2016;Watson et al. 1997 (26) and (28). The climate of deserts /Bw/ is noted only for the one site: (10), but the climate of the steppes /Bs/ is mentioned for the three properties: (7-8) and (12). One site nominated has been marked by a warm temperate (with a dry summer) climate /Cs/: (34), and three properties: (1, 2, 4) are described by the same warm temperate climate, but with a dry winter /Cw/. The warm temperate climate with uniform humidification /Cf/ has the most spread for the World Heritage karst areas: 13 sites. Cold temperate climate with uniform humidification /Df/ is appropriate for three properties: (13), (14) and (30).
The advisability of the new nominations to reflect the karst development «in cold regions, arid /semi-arid regions and tropical oceans regions, and to identify evaporite karst sites of outstanding universal value", was underlined by P. Williams (Williams 2008).

RUSSIAN wORLD KARST HERITAGE
As it was shown above, currently only one Russian natural karst object was inscribed on the List of World Heritage: the Lena Pillars Nature Park (30) (Butorin et al. 2012;Korzhuev 1961).
The uniqueness of the NPLP karst is predetermined by its development in the conditions of continuous permafrost up to 500 m thick, where the moisture condensation processes are the main factor of karstogenesis. On one hand, during spring and summer periods the soil layer actively condenses the water moisture from the air because of the considerable amplitudes of daily air temperature fluctuations, reaching 12.8°C. On the other hand, the condensation of moisture occurs on the lower part of the active layer as a consequence of big gradients (to 7.8°C per 1 m) between earth temperatures and lower situated perennially frozen rocks. As observed in a condenser created at the Melnikov Permafrost Institute (Siberian Branch of the Russian Academy of Sciences), 80 mm of water is condensed at the average in the Central Yakutia during the warm season (Shepelev 1980), constituting more than 30% of annual precipitation. Moreover, the permafrost blocks the quick filtration of precipitation into karst massifs. Thus, the accumulation of water, which in turn, causes the karst processes, occurs on the surface. This moisture, cooled almost to zero temperatures, is distinguished by a considerable aggressiveness in relation to karst rocks: since dissolved carbon dioxide (being also a leading factor of a karstogenesis) is characterized by the greatest solubility in cold water: the CO2 absorption coefficient is 0.665 at the solution temperature of 30°C, at the temperature of 15°C -1.019 and at 0°C is already 1.713 (Jakucs 1973).

DISCUSSION
As it was mentioned before, 37 karst properties are currently described by a high status of an outstanding universal value on the globe. Obviously, for Russia (where 8 karst areas, 22 karst provinces, and 57 karst districts are distinguished only on the Russian Plain (Chikishev 1978)) there is a considerable potential for natural karst sites of such high status, therewith, for example, both for conditions of sulphate (karst of the Belomoro-Kuloy Plateau in the Arkhangelsk Region) and salt karst (the Kempendyay salt springs in the Yakutia), that is more the areas considered are referred to the conditions of moderately cold climate with uniform humidification (Df ).
A remarkable example of a naked sulphate karst is developed in SE part of the Belomorsko-Kuloy Plateau located on the NW of the Russian Plain at 70-180 m above sea level. Lower Permian gypsums and anhydrites with a typical thickness 40-70 m are exposed here. The rocks have practically a monomineral composition: 95-98% consisting of CaSO4 x 2H2O (The Karst... 2011). The sulphate rocks of the Belomorsko-Kuloy Plateau are considerably karstified especially in wide-spread karst fields, socalled "shelopnyaky" by a local dialect where a density of the superficial karst forms (sinkholes, karst basins, small flat-bottom valleys) reaches extremely unique values: more than 3000 (The karst... 2011) per 1 km2. As it is described by A.G. Chikishev (1965): "Sometimes the crests separating the sinkholes are such narrow that it is impossible to across theirs without risk of falling down. The diameter of sinkholes is varied from 5 to 50 m and the depth is changed between 1.5-15.0 m".  (Uzemblo 1966).
First the description of the «ice» salt of the Kempendyay salt karstic springs was realized in 1828 by geologist I. Tchaikovsky (the father of the Great Russian composer P. I. Tchaikovsky). He noted that in summer period «winter crystals are destroyed and turn into a fine salt dust of the purest whiteness... which is can be taken and put in bags without any difficulty» (Dzens-Litovsky 1966).
The necessity of the researches, related with the preparation of new nominations for the Russian karst sites is determined by the anthropogenic pressure which is growing every year to karst landscapes being very fragile and vulnerable. For example, 2 July 2012 the above-described Buotamsky site of the Nature Park Lena Pillars was inscribed on the World Heritage List during the 36th session of the UNESCO but it is in the summer of 2012 in the Valley of Sinyaya (the Sinsky site of NPLP) a gabbro-diorite quarry was found in a few kilometers from the mouth of its right tributary: River Billyakh. However, already in 2013 the preparation of Sinsky site nomination was started under the influence of local population and at the support of the direction of the natural park. In fact the prompt work of Natural Heritage Protection Fund of Russia saved the nature of the Valley of Sinyaya from the destruction: after 39th session of UNESCO (25 June-10 July 2015) for which the Sinsky site nomination was supported almost unanimously, the further exploitation of the quarry was completely stopped.