Natural habitats as a part of the biological diversity of Bulgaria

Physical and geographical prerequisites for the diversity of natural habitats in Bulgaria. State and threats

Biodiversity conservation is closely linked to the conservation of natural habitats. Their preservation guarantees, to a large degree, the preservation of the plant, animal and fungi species associated with them. Bulgaria is a country with a rich and diverse nature. Its geographic location on the border between the temperate and subtropical zone presupposes to a high degree the diversity of its natural conditions - climate, water regime, soil and vegetation cover. Another factor is the relief, conditioned by the geological structure and the various morpho-tectonic structures: platform-like Danubian Plain, the parts of the young Alpine-Himalayan mountain system, the old land of the Macedonian-Thracian massif. These and other factors presuppose the great diversity of natural habitats in Bulgaria.


The present geo-morphological characteristics of Bulgaria are a result of a long-lasting evolution of its complicated geological structure. It consists of rock complexes of different age. Being part of the Alpine-Himalayan orogenic belt the relief of the country is very diverse. North Bulgaria is occupied by the Moesian hilly-plateau plain (Danubian plain) with predominantly lowland and plateau-hilly relief (a result of its platform structure) and a number of alluvial lowlands along the Danube. Its western part is dominated by large, flat areas separating the numerous rivers in the area. Its eastern part consists of the Ludogorie-Dobrudzha plateau, Popovo-Samuiloski heights (up to 501 m alt.) and Provadia-Lower Kamchia lowlands. The Balkan range, 530 km long, consists of the Forebalkan coulisse-like vertical slopes, separated by erosion and structural lowlands) and the main Balkan Range that consists of three parts. West Balkan Range, with maximum height of 2168 m, is a massive structure up to 45 km wide, with deep, karst morphographic levels to the south. Central Balkan Range is the most narrow one (up to 15 km wide), but in its highest part (2376 m) there are very well pronounced differences between the northern slopes (that are steep at their upper reaches and sloping in their lower part) and the southern slopes that are steeper and monolithic. The maximum height of the East Balkan Range is close to the altitude  of the hilly belt where the mountain loses its monolithic characteristics.

To the South of the Balkan Range is the transitional mountain-lowland area. Its relief is very complex, especially its western part, called Kraiste-Ihtiman area. It encompasses numerous mountains and lowlands whose hypsometric characteristics vary from 550 m alt. up to 2290 m alt. The northern part (Sredna Gora - Srednogorsko-Zadbalkanski subregion) is occupied by the West Balkan lowlands, while its eastern part is covered by the Upper Thracian – Mid-Toundzha subregion encompassing many alluvial lowlands and hills. The most southeastern part of Bulgaria is occupied by Sakar Mt. (556 m alt.) and Strandzha Mt. (710 m alt.). They comprise the Sаkar-Strandzha subregion. The Rila-Rhodopi massif is the main part of the Macedonian-Rhodopi mountain system. This area includes Rila Mt. (a dome-like massif that reaches 2925 m alt.) and Pirin Mt. (a sub-meridian horst reaching 2914 m alt.). Rhodopi Mts. are clearly divided into a western and eastern part. The  former one is  a system of high, flat, mountain ridges (Golyam Perelik summit – 2191 m alt.), that are deeply divided by a dense network of rivers and valleys. East Rhodopi Mts. are lower and have a more hilly outlook. Only a part of the Ossogovo-Belasitsa mountain system falls within the borders of Bulgaria (Ossogovska Mts. – 2251 m alt., Vlachina Mts. – 1824 m alt., Maleshevska Mts. – 1803 m alt., Ograzhden Mts. – 1523 m alt. and Belasitsa Mts. – 2029 m alt.) and occupy the most western and southern parts of the country. The territory of Bulgaria is almost 111 000 кm2. There are five hypsometric belts: lowlands – from 0 up to 200 m alt. (31,4% of the country’s territory), hills – from 200 up to 600 m alt. (41%), low mountains – between 600 and 1000 m alt. (15,3%), average-high mountains – from 1000 up to 1600 m alt. (9,8%) and high mountains – above 1600 m alt. (2,5%).

To the Еast, the territory of Bulgaria is occupied by the western periphery of the Black Sea Graben that is divided into a coastal shelf zone, continental slope and sea bottom. Each part has its complex morphology, some of which are of relict type. The karst covers approximately 23% of the territory of Bulgaria. The variety of karst relief together with the karst water bodies are the reason for the existence of many specific habitats characterized by typical soils, plant taxa and animal species. More than 5000 caves have been found in Bulgaria. They are the habitats of a diverse cave fauna (Vaptzarov et al. 1997). The northern part of Bulgaria is occupied by the Danubian Plain that consists of a Quaternary loess layer of different thickness. The relief is very specific, consisting of complicated layers that differ in age and origin. The soils are of chernozem type with strong A horizon with varying humus content.


A specific feature of the climate of Bulgaria is its diversity due to the fact that Bulgaria is in the transitional zone between temperate and Mediterranean climate types. From North to South the characteristics typical for the temperate climate transform into the characteristics of the continental-Mediterranean climate. Such a change is also observed from West to East, but the differences are significant only near the Black Sea coast. The border between the areas with annual snowfall (temperate) and the area with snowfall once every 5, 10 or more years (Mediterranean climate) crosses Bulgaria. The specificities of the climate due  to this transience between the two climatic regions of Bulgaria - temperate and continental-Mediterranean vary as a result of the impact of the country's complex topography (Nikolova et al. 1997).


The water resources of Bulgaria are based on river waters and to a limited extent on natural lakes and some larger springs. Rainfall is the main climatic factor upon which the river flow depends. The precipitation is high in the high-mountain belt, ca. 1100 mm/year. In the medium-high mountain belt it is 800–900 mm/year (in some places up to 1000–1200 mm/year), in the hilly foothill areas it is 700 mm/year on average, while in the lowlands it is 600 mm/year, but most of the water evaporates or infiltrates in the soil. Most productive in terms of water resources is the high mountain belt – 12,2% of the total water resources are generated on an area that is only 2,6% of the country’s territory. Richest in water is the Rila-Rhodopi area. It covers 16,7% of the territory of Bulgaria but its water resources are 39% of the total amount for the country. The Balkan Range and the Forebalkan rank second. The annual distribution of precipitation is uneven. The winter precipitation is mainly snow in the higher parts of the mountains and its quantity in spring and early summer coincides with the maximum rain falls in May and June in the areas with moderate-continental climate where the minimum is in February. In areas with continental-Mediterranean climate (except for their highest parts) the maximum precipitation is in autumn and winter. The strong aridisation in summers is typical for the continental-Mediterranean climate.

The high amplitudes in the water level of the Danube along Bulgaria’s northern border are an important factor for the level of the underground waters in the lowlands along the river. The underground waters have an impact on the features of the habitats inland. The karst and their water bodies are also among the natural landscape factors responsible for the water resources of Bulgaria together with geomorphology, climate, soil type and vegetation. In some cases they increase the water resources of an area (Devnya, Ponor, Vratsa, Pirin-Razlog area, Dobrostan area, etc.), and in others they reduce it (Ludogorie and Dobrudzha areas). The number of lakes in Bulgaria is high (the number natural lakes is between 300 and 400, some of them being temporary), but they cover small areas and are shallow. However, they are an important group of habitats for rare animal and plant species and conenoses. The coastal lakes are mainly lagoons and limans, important habitats for the birds nesting there. There are ca. 330 glacial lakes in Rila and Pirin Mts. which occur above 2100 m alt. The karst lakes are mainly in the Forebalkan. A few lakes have tectonic origin, others are a result of land slides or occur by the rivers. Most of the lakes are fresh-water ones. Only some of the coastal lakes are saline. About 2000 water reservoirs have been built for the management of the surface waters and the river flows in the country.

The marshy areas differ in range, type and water regime. Some of them are lakes that have reached the last stage of being overgrown with plants or blocked with mud (mainly along the Black Sea and along the Danube). Others occupy the low parts of denudated flat areas in the mountains (in some of them the water comes from the adjacent slopes) or in the low parts of the kettle holes. The fens and mires are widely distributed and very often temporary, or their surfaces are reduced during the summers. Temporary marshes also occur beside large rivers during periods of high waters. While some temporary marshes depend on the dynamics of the underground waters, others are of karst origin (Zyapkov et al. 1997).


The soils in Bulgaria vary largely according to their origin and composition, and the soil cover has a complex spatial structure. Eight higher orders are found here, according to the “Legend to the world map of soils” (FAO 1988, 1990).

The Luvisols (LV), followed by the Vertisols (VR) and Planosols (PL) are most widely distributed in the lowlands, plains and hilly areas of Bulgaria. Solonetz and solonchaks and little deposit soils also occur in these areas. Second in distribution are the areas with soils with high accumulation of basic organic components – mainly in the areas along the Danube and in Dobrudzha area. Most restricted are the areas with Chromic Luvisols, Alisols and Regosols in the areas with Mediterranean characteristics. In the mountains of Bulgaria, from 700–800 to 1800–2000 m alt. is the belt of Cambisols. The belt of Mollic Cambisols is between 1800–2000 and 2500 m alt., while the belt of Umbrosols is above 2500 m.

Bulgaria belongs to two European soil-geographical regions: Carpathian-Danubian (Lower Danubian subregion) and Mediterranean region. The first region encompasses the areas with Chernozems and part of the areas with Luvisols in north Bulgaria. The Mediterranean soil region encompasses the territories to the South of the Balkan Range. It is characterized by a higher diversity of the soil types – Luvisols, Pelic Vertisols, Leptosols, Alisols and soils that have relic features and are identified with the soils from North Bulgaria (Chromic Luvisols, LVx, Nitisols etc.). The areas with shallow soils (Leptosols, LP) are also large (Ninov 1997).

Flora, vegetation and cover

The combination of the abiotic factors of the environment of a certain area predetermines the composition and structure of its biotic component. The most complete expression of this complex relationships are the plant species (the flora) and the plant communities (the phytocoenoses).


The Bulgarian vascular flora comprises 60 fern species and 3840 species of seed plants. Presently the endemic element of the country is 12,8% (498 species from 43 families). Of these, 186 species (4,8%) are Bulgarian endemics, the biggest part of which is concentrated in Rhodopi, Rila and Pirin Mts. and the Balkan Range. These areas are richest in Balkan endemics as well. The Balkan endemics are 312 species (8%). Bulgaria is also rich in relic species, including some from the Tertiary period. Many vascular plant species (ca. 700) are of restricted distribution: ca. 13% occur only in one floristic region and some of them in only one locality; others occupy small territories with small populations. For still others, their Bulgarian localities are at the peripheries of their areas of distribution. Five hundred-fifty-eight  species (15%) are protected by the Biodiversity Act of Bulgaria. The IUCN Red List of Threatened Plants (Walter & Gillett 1998) includes 106 species (2,7%) from the Bulgarian flora. Annex 1 of the Bern Convention (1979) includes 50 species from Bulgaria, 21 species are listed in the Habitats Directive 92/43 ЕЕС, and 67 are present in the CITES List (Petrova et al. 2005). The anthropophytic flora includes 560 species (14%), some of which are invasive and very aggressive alien species, and in many places threaten the autochthonous vegetation; the invasion of alien species into the Bulgarian flora still continues today (Petrova et al. 2005).

The bryophyte flora of Bulgaria includes 719 species. The species diversity is richest in the Rila Mts., followed, in descending order, by Pirin, Vitosha Mts., West and Central Balkan Range, West and Central Rhodopi Mts. Approximately 40% of these species are critically endangered, endangered or vulnerable according to the IUCN criteria (2001). Of all 173 species of liverworts, 11 are critically endangered, 16 are endangered, and 33 are vulnerable (Ganeva & Nacheva 2005).

Vegetation and vegetation cover

From vegetation-geographical point of view the vegetation cover of Bulgaria is a complex of Boreal, Central-European (most widely distributed), Steppe (second in frequency), Arctic, Alpine, Balkan (including Mediterranean) and local vegetation. Representatives of all ecological groups related to water occur in the Bulgarian vegetation. The species vary considerably according to the temperature and edaphic factors. The acidity of the bed rock and soils in some cases is a major factor for the development of specific plant species and determines the structure of the phytocoenoses. According to the phytogeographic and geobotanical information available, Bulgaria is divided into three zones: the European nemoral zone (deciduous, broad-leaved forests) encompassing the Euxinian, Ilirian (Balkan) and Macedonia-Thracian areas. The Eurasian steppe and forest-steppe zone is represented by the Lower-Danubian province, while the zone of Mediterranean xerophyllous forests is represented by the East Mediterranean province (Bondev 1997, 2002). According to the biogeographical division of Europe (European Topic Centre on Biodiversity and Nature Protection), accepted by the European Commission and the basis of the Habitat’s Directive (92/43/ЕЕС), Bulgaria belongs to three biogeographical regions: Alpine, Continental and Black Sea regions. All mountain belts that occur in Central Europe are present in the Bulgarian mountains as well, excluding the nival one. The Bulgarian vegetation has certain peculiar characteristics when compared to the Central-European one, as a result both of the specific features of the Balkan vegetation and of a number of local characteristics. Some authors (Grebenshchikov 1957; Lavrenko 1950, 1964) consider that affiliating the mountain belts from North and South Europe is not correct. This explains the differences in the differentiation of the subalpine belt by the Bulgarian authors (Velchev 1997) and the ones from West Europe (Ozenda 1985, 2002). The Bulgarian authors identify subalpine shrub belt that is defined by the western European botanists as an upper subalpine sub-belt and a coniferous belt that is considered in the western botanical literature as lower subalpine subbelt. A typical alpine belt can be found in Rila Mts. In Pirin Mts. it is of more limited distribution and  occurs only as fragments in the mid-high mountains of Bulgaria as well as in other Balkan mountains. The herbaceous and dwarf-shrub vegetation of the alpine and subalpine belts are dominated by a considerable number of Balkan endemics (Sesleria comosa, Festuca riloensis, F. valida, F. penzesii, etc.), and some local endemics (Primula deorum, Carex tricolor, C. parviflora, C. bulgarica, Sesleria korabensis, etc.) together with arctic-alpine and alpine species (Carex curvula, Festuca airoides, Juncus trifidus, Cetraria islandica, Salix herbacea, Vaccinium uliginosum, etc.). A major component of the shrub vegetation in the upper subalpine subbelt are the phytocoenoses of Pinus mugo and Juniperus sibirica. The endemic coenoses of Chamaecytisus absinthioides also occur. The most remarkable herbaceous endemics are Primula deorum, Festuca valida, F. penzesii, F. balcanica, F. pirinensis etc. In the coniferous belt (the lower subalpine sub-belt according to the West European definition of the belts), together with Picea abies and Pinus sylvestris which are widely distributed in Europe, occur also Pinus peuce (Balkan endemic)and P. heldreichii (Balkan subendemic). The communities of P. peuce are very close to the mesopyllous ones. They prefer silicate bedrock and the composition of the foot layer is similar to that of the spruce forests (Vaccinium myrtillus, Luzula sylvatica, Calamagrostis arundinacea etc.). The phytocoenoses of Pinus heldreichii are xerothermic, develop on alkaline rocks and their composition includes Mediterranean species (Festuca penzesii etc.). It is accepted that the coniferous forests in the lower subalpine sub-belt are of subarctic type, while the beach coenoses in the mountain belt have Central European features. However, phytocoenoses with Laurocerasus officinalis, Haberlea rhodopensis and other endemic and relic species like Acer heldreichii also occur in the beech forests of Bulgaria. Many authors split Fagus sylvatica into subsp. sylvatica and subsp. moesiaca, and the fir Abies alba is split intosubsp. alba andsubsp. borisii-regis. The southern border of the distribution of the first subspecies is in the most southern Bulgarian mountain Slavyanka Mt. (Ali Botush), and subsp. borisii-regis occurs in the mountains in the SW part of Bulgaria, and the northern part of Greece, but rarely acts as edificator. In the lowest parts of the Bulgarian mountains scientists describe the horn beam – sessile oak belt, fragments of which exist also outside mountains. The vegetation in this belt has features related to the Mediterranean forest vegetation. It is dominated by Fagus sylvatica subsp. moesiaca, Carpinus betulus, Quercus dalechampii, Fraxinus excelsior, Acer pseudoplatanus, A. hyrcanum etc., and species such as Ostrya carpinifolia, Castanea sativa, Aesculus hippocastanum, Tilia tomentosa, Pinus nigra subsp. pallasiana, which are absent or almost absent in Central Europe. The vertical distribution of the vegetation cover in the different mountains also differs throughout Bulgaria. In the Balkan Range the coniferous belt is poorly developed, and it is dominated by the beech tree. In Rhodopi and Vitosha Mts. the dwarf pine is limited and there are fragments of alpine vegetation. Calcareous rocks are dominant in some mountains and in others, silicate ones. Respectively, the vegetation has its specific features in the different habitats.

The phytocoenoses of the South Euxinian species have particular place in the Bulgarian vegetation. They occur in Strandzha Mts. and the East Balkan Range. The forests of Fagus orientalis and Quercus polycarpa are a complex composition of South Euxinian and Central European species: Rhododendron ponticum, Laurocerasus officinalis, Daphne pontica, Vaccinium arctostaphylos, Trachystemon orientalis, Calluna vulgaris, Festuca drymeja, Acer platanoides, A. campestre, Carpinus betulus, Tilia tomentosa, Quercus cerris, Crataegus monogyna, Poa nemoralis etc.

The forests of Quercus cerris, Q.frainetto and Q. pubescens in the hilly plains of the country occur in the southeastern part of the nemoral zone and include southern species. The xerothermic oak forests with separate coenoses of Fraxinus ornus, Carpinus orientalis etc., have clear Mediterranean features. Cotinus coggygria, Paliurus spina-christi, Juniperus oxycedrus, J. excelsa, Colutea arborescens, Coronilla emerus, Clematis flammula, Anemone pavonina, Ranunculus rumelicus, Cyclamen hederifolium etc. also occur. Some of the shrub species make coenoses that are very widely distributed. Sometimes the coenoses of Genista rumelica, G. lydia and other southern species, or local endemics such as Astracantha aitosensis and A. thracica also occur.

The relic coenoses of the steppe species Amygdalus nana, Artemisia lerchiana, Stipa lessingiana, Paeonia tenuifolia, Caragana frutex etc. are also of particular interest. The distribution of the Pontic-Pannonian continental loess and sand steppes is limited but very important for the Bulgarian biodiversity. The occurrence of oro-Mediterranean coenoses of small, spiny shrubs (Astragalus angustifolius,etc.) and subcontinental shrub coenoses are also typical for the Bulgarian vegetation. The evergreen communities of Quеrcus coccifera penetrate along the valley of Struma river in Bulgaria, and other southern species also occur (Phillyrea latifolia, Pistacia terebinthus etc.), some of which are also edificators or dominants. The structure of the herbaceous vegetation is also very complex. Many semishrubs participate especially in calcareous and eroded areas. The area of the mesophytic (meadow) herbaceous vegetation dominated by Festuca pratensis, Cynosurus cristatus, Lolium perenne, Poa sylvicola etc. decreases progressively. After the destruction of the forests the xeromesophytic and xerophytic coenoses of Chrysopogon gryllus, Bothriochloa ischaemum (= Dichantium ischaemum), Poa bulbosa, Stipa spp., Festuca valesiaca, Artemisia alba, Satureja montana, Agropyron brandzae etc. develop more often. In most of the cases the vegetation cover is a complex of shrub and herbaceous coenoses.

Preserved forests of Quercus pedunculiflora, Q. robur, Fraxinus oxycarpa, Ulmus minor and other mesophytic and hygrophytic tree species occur more and more rarely in the lowlands of the country. The distribution of the swamp and marsh coenoses of Phragmites communis, Typha sp. div., Schoenoplectus sp. div., Nymphaea alba, Nymphoides peltata, and Nuphar lutea has also decreased.

To the diversity of the vegetation cover is added the halophytic (including in some inland parts of the country) and psamophytic vegetation. The halophytic coenoses are most often dominated by Puccinellia convoluta, Limonium gmelinii, Aeluropus littoralis, Salicornia europaea, Camphorosma monspeliaca, etc. A considerable number of rare and endemic species occur in the psamophytic coenoses of Leymus racemosus, Ammophila arenaria, Galilea mucronata, Aurinia uechtritziana, Artemisia campestris etc. that nowadays are subjected to complete destruction. The coastal reefs and rock outcrops in the country are the habitats of very rare phytocoenoses and endemic species.

The identification of the habitats in Bulgaria and their affiliation to the EUNIS classification (including the existing units in the Manual for the 27 EC member-states to the Habitats Directive for NATURA 2000), or other classification schemes of the habitats in the EU requires detailed knowledge of the specificitiess of the Bulgarian nature due to its transitional position between Central Europe and the Mediterranean. One of the main obstacles is the absence of a complete classification scheme based on the sigmatic school. This fact in some cases makes very difficult the interpretation of habitat taxa identified in other European countries in the context of the designation of the specific habitats for the region and our country is fraught. According to the information existing today the higher syntaxa include 40 classes, that are of pan-European distribution. Of all 67 orders some are of Balkan distribution, such as Seslerietalia comosae for instance. Among the alliances (ca. 93 for Bulgaria) the regionally specific units are higher – Cirsion appendiculati, Potentillo-Nardion, Ramondion nathaliae, Veronico-Papaverion degenii, Seslerion comosae, Pimpinello-Thymion zigoidi,etc. Bearing in mind that most of the plant associations in Bulgaria are of regional or local distribution one can say that further studies dedicated to the elaboration of a complete classification will lead to the discovery of other endemic syntaxa. The complete classification of the plant vegetation in Bulgaria according to Braun-Blanquet (1964) will outline more distinctly its specificitiess and will allow a more efficient protection of the habitats and their components.

State of the vegetation and its threats

Natural dynamic processes observed in the vegetation cover of Bulgaria are the succession of the herbaceous coenoses into shrub and even forest vegetation. There exist tendencies towards the restoration of a more autochthonous herbaceous vegetation in places of secondary herbaceous communities of Nardus stricta, Bothriochloa ischaemum, etc. The anthropogenic impact has caused afforestation of considerable parts of the country independently of the altitude. However, the most strongly changed natural environment is in the lowlands. A fragmentation of large forests has occurred here: the quality and structure of these forests are damaged and some of them have become shrub formations. Most of the deciduous forests have been turned into coppice forests. The steppe vegetation in its largest part is destroyed. Secondary communities of Carpinus orientalis, Paliurus spina-christi, Juniperus communis, Poa bulbosa, Cynodon dactylon, Chrysopogon gryllus, Bothriochloa ischaemum, Festuca valesiaca, F. rubra, Pteridium aquilinum etc. are widely distributed. The shrub-herbaceous complexes are also widely distributed, and the erosion rate has increased. Some communities of Quercus coccifera, Acer monspessulanum, Juniperus excelsa etc. have been turned into understocked forests (stocking less than 0.4) or have been replaced by the coenoses of Juniperus oxycedrus, Paliurus spina-christi, Bothriochloa ischaemum, Poa bulbosa, etc.

The changes in the water habitats of the lowlands are disastrous – the water bodies are completely or almost completely dry, the river beds have been changed and many riverside habitats have been destroyed. At the same time a large number of new artificial water bodies and irrigation systems have been built. Some mobile plant communities together with their accompanying fauna have conquered them.

The high mountain vegetation, that has been until recently less damaged, is also strongly destroyed. Although the natural components in the mountains are very vulnerable, non-nature-friendly activities have taken place. They are related to tourism and have caused nature destruction and threats to many biocoenoses and habitats. Precious habitats along the Black Sea coast with hygrophytic, hydrophytic and psamophytic vegetation and the related fauna are completely extinct or soon will be extinct. Enormous efforts and money are necessary to restore the habitats and biodiversity in Bulgaria.


Until today 4900 fungi species have been registered for Bulgaria and more species are expected to be discovered. The diversity of fungi-like organisms and fungi whose genetic resource includes also the micro- and macromycetes is assessed, studied and protected on the basis of a complex approach. As a result of the unregulated collection of macromycetes in Bulgaria, their conservation gains priority (Denchev et al. 2005).


Bulgaria is inhabited by a rich and diverse fauna that is a consequence of the cross-roads position of the country between central Europe, the Mediterranean, Ukraine-Kazakhstan steppe, and Asia Minor – Caucasus regions. North European, Steppe and Mediterranean animal species occur in Bulgaria. Bulgaria is in the centre of the Balkan Peninsula which is one of the major centres of speciation in Europe. A considerable part of the fauna are Balkan endemics, especially among the species of conservation interest. The Black Sea fauna includes relic species, species which have migrated from the Atlantic Ocean through the Mediterranean Sea, as well as animals that have invaded from other parts of the world’s oceans, and they have a considerable impact on Black Sea ecosystem.

The fresh water fauna includes representatives of ten animal groups with a very high number of species – unicellular animals, water fungi, cnidarians, ctenophores, flat worms, round worms, kinorhynchus, rotatorias, etc. This diversity is still not well investigated (Golemanski et al. 2005).

The arachnids are particularly sensitive to the changes of the environment (scorpions, spiders, etc.). They also are not very well studied although it is known that among them exist a number of Bulgarian and Balkan endemics, some of which are threatened by extinction (Deltshev et al. 2005). All orders and suborders that can theoretically be expected to occur in Bulgaria have been summarized. Their species diversity is exclusively high. The entomological fauna of Bulgaria is also very rich. The insects that occur in Bulgaria belong to two classes, 30 orders and 583 families with tens of thousands of species including a number of Bulgarian and Balkan endemics and relics (Beron 2005а). The malacofauna of Bulgaria is represented to date by 445 species. Approximately 25% occur in the Black Sea, 21% are in the fresh water bodies and 54% are on the land. Some of the taxa are of conservation importance (Hubenov 2005). The fishes are among the most important systematic groups of animals (and the largest natural animal resource in the world) of which 218 species from 59 families occur in Bugaria. In the Red Data Book of Bulgaria (1984) 22 species are included, while in the World Red Data Book (IUCN) 51 species from the Bulgarian ichthyofauna are included (Zivkov et al. 2005).

Bulgaria is among the countries in Europe with the highest diversity of reptiles and amphibians – 56 species are recorded (7 species of caudate amphibians, 12 species acaudate amphibians, 6 species of turtles, 13 species of lizards, 18 species of snakes). Two snake species have disappeared in the last century and of two species of sea turtles, only single individuals can be registered nowadays. All 52 species that occur in Bulgaria are included in the Annexes of the Bern Convention, 42 are protected by the Biodiversity Act, and 12 are in the Red Data Book of Bulgaria (1984) as “rare” and “endangered” species. As a result of the anthropogenic pressures, the status of some species continues to deteriorate (Biserkov 2007, Biserkov et al. 2005).

Some of the richest ornithological sites in Europe are located in Bulgaria. The conservation of birds is among the major priorities for conservation of the Bulgarian biodiversity. The conservation of their habitats is a priority issue since this is one of the most efficient mechanisms for the conservation of birds (Ivanov & Iankov 2005). Bulgaria is also listed among the European countries that are richest in mammals, with a record of approximately 100 species. To this number belong also animals dependent on man and species that are of doubtful occurrence in Bulgaria (Popov & Sedefchev 2003). Among these, 46 species are of conservation importance (Popov et al. 2007). Particular attention is given to the preservation of the habitats of bats, which are among the groups of vertebrate species that need urgent protection. This is the result of a trend of rapid decrease of numerical strength and species diversity. There are 13 areas in Bulgaria that are of particular importance for the conservation of mammals and other animal groups. The animals are a subject to protection under the Biodiversity Act. However, very often, in many regions like Strandzha, West and Central Rhodopi mountains, the economic interests are so strong that the conservation of mammals and other animal species is neglected (Spiridonov & Spassov 2005). Bulgaria is very rich in caves and the preservation of their biodiversity is a priority issue. It requires strict control to decrease the anthropogenic impact; the damage or destruction of the natural habitats, disturbance of bats, and the direct and indirect killing of animals, have quantitative and qualitative impacts on the species included in the Bulgarian fauna (Ivanova 2005; Beron 2005b).

Many of the animal species are the subject of economic exploitation that causes threats to and reductions of their populations. Further studies are needed for the less investigated species and the species of conservation importance – studies on the dynamics and numerical strengths of their populations, the parameters that ensure sustainable use of the economically important animals. To protect these species, the most important step is the preservation of their habitats.

The existing network of protected areas will play an important role for the preservation of the natural habitats and their components in Bulgaria, if the laws are efficiently put into force by the state authorities. The creation of the European ecological network NATURA 2000 will play an important role for the conservation of the Bulgarian nature if the measures recommended by the scientific community are applied in reality. This is the goal of volume 3 of the Red Data Book of the Republic of Bulgaria.

Veska Roussakova