Red Data Book of the Republic of Bulgaria -> Volume 3 - Natural habitats

Concept and methodology

Classification and nomenclature of the natural habitats

The main approach of the contemporary concept for nature conservation and protection of wild plant and animal species is to protect their habitats.

The habitats are separate units of the biosphere and an important element of biodiversity. They are of priority importance in major European and global nature conservation documents: Convention on Biological Diversity (1992), Pan-European Strategy for the Protection of the Biological and Landscape Diversity (1996), Directive 92/43 of EEC for the conservation of habitats and wild flora and fauna (1992), Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention) and Resolution № 4 of the same Convention (1996).

In Volume 3 Habitats of the Red Data Book of the Republic of Bulgaria are presented the habitats of conservation value at national and international levels. The National Biodiversity Act (2007) defines “natural habitat” in the Directive 92/43 of ЕЕС; it postulates that “natural habitat means terrestrial or aquatic areas distinguished by geographic, abiotic and biotic features, whether entirely natural or semi-natural.” It differs from “species habitat” which means “an environment defined by specific abiotic and biotic factors in which a species lives at any stage of its biological cycle.” According to Meshinev & Apostolova (2005) the term “natural habitat” has become popular enough and can be used on equal basis with the term “nature habitat”. The attempts to make  habitat classifications have long history. The first list of European habitats was prepared in 1985 – 1990 within the frame of the project CORINE Biotopes. It represents the first, relatively complete, classification of habitats in the territory of the European Union (Moss et al. 1991). Its preparation was based on the work of leading phytocoenologists and phytogeographers such as Ellenberg (1963, 1988), Horvat et al. (1974), Gehu (1984), Ozenda (1985), Noirfalise (1987), Peinado Lorca & Rivas-Martinez, (1987), Oberdorfer (1990), and Rodwell (1991). A leading role in the preparation of this classification was played by the Royal Institute for Natural Sciences, in Belgium. After the the Central and East European countries joined the EU, a need for further development and enrichment of the habitat classification scheme appeared. With the participation of scientists from non-EU countries and with the leading role of the above mentioned institution, the Palaearctic Classification of habitats was developed (Devillers & Devillers-Terschuren 1996). Although it has been updated several times, after the elaboration of the European Nature Information System – EUNIS ) it was decided that a new classification was necessary (Davies & Moss 1997), which should be based on the hierarchical principles of the Palaearctic Classification but would also correct its mistakes and add the new, missing information. New marine and urbanized habitats have been added to the EUNIS Habitat Classification and the characteristics of the existing habitats have been further developed. This classification establishes links with CORINE Land Cover ( and the phytosociological alliances of the European vegetation (Rodwell et al. 2002). In the EUNIS database ( there are links with other habitat classifications as well, including the classification in the Habitats’ Directive, which covers the habitats (with four-figure codes) that are included in the European Ecological Network NATURA 2000. EUNIS is the most complete pan-European habitat classification and it serves as basis for standard descriptions and collection of data across Europe applying criteria and keys for habitat designation. It includes all habitats, natural and man-made, terrestrial and marine ones. According to EUNIS, “habitat type” (respectively “natural habitat”) is “plant and animal communities as the characteristic elements of the biotic environment, together with abiotic factors operating together at a particular scale.” All factors which are present in the definition are included in the description part of the habitat classification. The scope of the EUNIS classification is limited to level 3 from the hierarchical system (to level 4 for the marine habitat types). The EUNIS data base is maintained and updated by the European Topic Centre for Nature Protection Biodiversity (ETC/NPB) in Paris, European Environment Agency (EEA) and European Environmental Information Observation Network (EIONET). The last comprehensive revision of the EUNIS classification was made by Davies et al. (2004). EUNIS classifications served as the basis for the preparation of the habitat descriptions in the current volume. The authors have had the right to modify the habitat names to a certain degree so that they can reflect more precisely the habitat diversity in the country and at the same time make them more understandable to the public. The authors could develop sub-types and types that do not exist in the EUNIS classification but have been established in Bulgaria. The need of a more flexible approach during the identification of the habitats stemmed also from an objective reasons: the lack of a complete vegetation classification following the sigmatic school of Braun-Blanquet (1964), i.e., the basis for the designation of a considerable part of the habitat units in all classifications, including EUNIS.

Threat criteria and categories

Threat criteria and categories have been developed following the criteria of the IUCN but also taking into consideration the specificities of the habitats as elements of biodiversity. The methodology for the designation of NATURA 2000 sites has also been used together with some recent scientific and applied papers which have been elaborated within the framework of similar projects in other European countries: Serbia (Lakušic, ed. 2005), Romania (Donita et al. 2005, Gafta & Mountford, 2008), Czech Republic (Chytrý et al.  2001), Italy (Petrella et al. 2005, Poldini et al. 2006), Austria (Essl et al. 2002, Taxler et al. 2005), Slovakia (Stanova & Valachovic 2002), etc.

The threat assessment for each habitat is based on the best expertise supported by specific criteria.The lack of a standard system for habitat assessment (like the system for species assessment of IUCN), the relatively limited international expertise and last, but not least, the low level of the studies of the syntaxonomic diversity of the vegetation in Bulgaria according to the Braun-Blanquet school. An important deficiency is also the lack of a complete mapping of the habitats or plant syntaxa of the country. These reasons do not allow the use of quantitative criteria for the designation of the area coverage, the percent of fragmentation, etc. The qualitative criteria are of major importance: they include not only data about the distribution of a certain habitat in the country but also its conservation significance at national and international level. As habitats of conservation importance are determined the units that are of European significance, i.e. the ones included in Annex I of the Habitats Directive 92/43/ЕЕС, the Bern Convention, etc. The second group includes habitats of national significance, whose phytocoenoses are dominated by or include a considerable number of Bulgarian and Balkan endemics, relics, species for which Bulgaria is in the periphery of their distribution area (e.g. forests of Quercus coccifera, shrubs of Phillyrea latifolia, etc.), rare geological phenomena (serpentine rocks and their flora and fauna), water bodies with rare abiotic characteristics for Bulgaria, and habitats whose distribution in Bulgaria have suffered from drastic negative changes as a result of the human activities (cutting, ploughing, draining, eradication, etc.). Such habitats are the steppes and meadows, lowland forests, marshes and mires, and river and riverside ecosystems. To determine the threats and the respective category of each habitat type 10 criteria with different variables have been used. The combination of these criteria and their variables are given in a formula that is related to each category.

?. Conservation significance

B. Geographical (general) distribution

C. Distribution in Bulgaria

Distribution in Bulgaria is listed according to the geo-botanical zoning of Bondev (2002):

D. Area covered by the habitat

This is the approximate area that the habitat covers in Bulgaria. The evaluation of the habitat area is based on the comparison with the areas of the main habitat units from CORINE Land Cover.

?. Fragmentation

When the habitat is fragmented the reasons for this fragmentation is assessed, i.e. whether it is of natural origin or is a result of a negative human impact in the last 100 years. This fragmentation can be classified as follows:

F. Changes in the area covered and fragmentation

The negative changes in the area of distribution and the degree of the habitat fragmentation in the last 100 years can be assessed in the following way:

G. Changes in the habitat structure

The qualitative structure (species composition and ecological parameters) of the habitat has changed in the last 100 years. These changes can be:

H. Restoration capacity

The restoration capacity of the habitat can be classified as follows:

I. Role in the preservation of species of conservation significance

This criterion indicates the  presence of species of conservation importance that are typical for the habitats, including dominants and edificators, which are included in Annexes and Lists of IUCN, CITES, Bern Convention, Directive 92/43, Biodiversity Act (2007), Red Data Book of Bulgaria (Velchev 1984), Red List of vascular plants (Petrova & Vladimirov 2009), mosses (Natcheva et al. 2006) and fungi (Gyosheva et al. 2006). To apply this criterion it is recommended that at least two of the present species are from the Bulgarian Red Data Book, Annex № 3 of BDA, Red Lists and CITES, and only one species is critically endangered from the Red List or from IUCN lists, and the Annexes of the Bern Convention and Directive 92/43.

J. Stability

The habitat has natural stability and dynamics under the impact of different environmental factors: circulation of the level of the underground and aboveground waters, soil-slides, storms, wind and water erosion, etc.

L. Resource importance

Threat categories of the habitats

On the basis of the above criteria the following threat categories have been assigned to the habitats that correspond to the threat categories for the species:

Extinct (EX)

When the area of distribution is destroyed (caused by draining, ploughing, flooding, urbanization, extraction of inert materials, etc.) or when the structure, parameters and functions of the habitat is changed to  such a degree that the initial habitat has disappeared.

Critically endangered (CR)

Formula: C3 D3 E3 F3 G3 H3 or H2 L2. The habitat is critically endangered when it can completely disappear if no special measures for its protection are taken, and corresponds to a minimum of five of the following conditions:

Endangered (ЕN)

Formula: C2 D2 E2 F2 G2 H2 or H3 L2. The habitat is endangered when there is a real threat that a significant part of it will be destroyed in the near future and it corresponds to minimum five of the following conditions:

Vulnerable (VU).

A habitat is vulnerable when there is no direct threat that can cause its extinction but there are factors that can cause serious changes in its quality. The habitat assessment have to correspond to one of the two combinations of criteria listed below.

First option – formula B1 and/or B2 C1 D2 E2 F2 G1 H1 L1:

Second option – formula B1 and/or B2 C1 D1 E1 F1 G2 H2 I J L3:

Note: It is required that the assessment of the habitats is compliant with at least half of the options listed above.

Nearly threatened (NT)

Formula A1 and/or A2; B1 and/or B2 I J C1 D1 E1 F1 L2, L1: The habitat is nearly threatened when there is no real danger for its extinction but there are factors which can cause changes in its characteristics and the habitat corresponds to the following combinations of conditions:

Structure of the habitat articles

Each article for a habitat has the following structure:

Running header, that shows the affiliation of each habitat to the following major groups: marine habitats, coastal habitats, inland water bodies, mires, bogs and fens, herbaceous communities and communities of lichens and mosses, shrub communities, forests, inland rock habitats. The main habitat groups correspond to the main habitat types from level І of the hierarchical EUNIS classification, that is given in its electronic edition - (


Code and name of the habitat. The habitat code is introduced for convenience and consists of a current number that shows the place of the habitat in the main group and word-number combination that shows its affiliation to the main habitat group and the respective hierarchical level in the cited classification. The Bulgarian names are based on translation of the English terms in the original version of the ЕUNIS classification. The names steppe, garrigue and phrygana are used according to Davies et al. (2004).

Relationships with habitat classifications. The first code and name (in English in the original) in this rubric is the corresponding habitat type according to the EUNIS classification (abbreviated EUNIS). Then follows the relationships with the codes and names from the Palaearctic Classification of the habitats (abbreviated PAL. CLASS.) and from the Directive 92/43 (abbreviated HD 92/43). Finally, the relationship with the geobotanical classification units of the compilation “The vegetation of Bulgaria. Map 1:600 000 with explanatory notes” (Bondev 1991) is given. In the cases related to halophytic vegetation, the publication of Ganchev et al. (1971) is used, and for the vegetation in the water bodies in Bulgaria, the work of Kochev & Jordanov (1981) is used.

Conservation status. European and national legal documents where the respective habitat name exists are given in the following order: Biodiversity Act (BDA), Bern Convention (BC) Directive 92/43. (HD).

Category. The threat category is given together with the corresponding formula.

General characteristics. This part is in a text format presenting the characteristics of the respective habitat, including the description of the habitat, its area of distribution (geographical affiliation), main vegetation type (described syntaxa – at subassociation, association and/or alliance rank – according to the author’s decision), habitat subtypes (when one habitat has several distinctive subtypes). The orographic characteristics, soil types, vertical and horizontal specificities of the vegetation, the major plant species (edificators, dominants and subdominants, more frequent species, typical for the habitat), and dynamics (fluctuations and succession peculiarities) of the vegetation are given.

Characteristic taxa. Two sub-categories are given: plants and animals/fungi. When the habitat has several subtypes the characteristic species are given for each subtype separately. The term “characteristic taxa” is not equal to the “characteristic (diagnostic and/or differential) species” according to Braun-Blanquet (1964) and the Code of the Syntaxonomical Nomenclature (Weber et al. 2000). This term is more general and includes both taxa that occur only in the respective habitat and taxa with wider distribution outside the borders of the specific habitat. Hence, “characteristic taxa” are the typical species: dominants, constant species (with high frequency) and diagnostic species for the respective habitat. The name of the vascular plants are according to Delipavlov & Cheshmedzhiev (2003), the mosses are according to Ganeva & Natcheva (2003) and Natcheva & Ganeva (2005), and the lichens according to Mayrhofrer et al. (2005).

Distribution in Bulgaria. The distribution of the habitat within the country and the maximum altitude at which it occurs are given.

Conservation importance. The conservation importance of the habitat is assessed and the reasons for this are given; e.g., when it is important for the protection of a rare plant, fungus and animal species, etc.

Threats. The major threats have been presented based on the classification used in the assessment and inventory of the protected sites from the European Ecological Network NATURA 2000. Depending on their strength some of the threats are given in details and others are only mentioned.

Conservation measures taken. The classification of the species conservation measures of IUCN has been used. Important protected areas and NATURA 2000 sites in which representative parts of the habitat are preserved are given.

Conservation measures needed. The basis is the classification of thethreats of IUCN. New protected areas important for the conservation of the respective habitat have been suggested in some descriptions.

Illustration of the habitat. The habitats are illustrated by photos. One or two photos give the general view of the habitat. When the habitat has subtypes each subtype is also illustrated by one photo each.

Map. The habitat distribution is mapped on 10х10 km UTM-Grid maps. The maps are indicative and give general information about the habitat distribution. The accuracy corresponds to the present level of knowledge for each habitat. For a number of habitats the mapping is precise and recent, but there are habitats for which, together with the precise information available, territories of possible occurrence are also given. The scale and grid also presuppose the indicative character of the maps. For activities that need more precise mapping (e.g. Strategic Ecological Assessment, compatibility assessment, management plans for protected zones and sites, etc.) these maps can have only an indicative role and further studies are required for the identification, localization and mapping of the habitats in a certain area. The software MapSoftV1.exe (Lubenov & Biserkov 2005) was used for mapping. It is available from MapSoftV1 is a extension of ArcGIS. The shapefiles of GIS models of the distribution of the habitats have been elaborated within the project “Development of the network of protected areas NATURA 2000 in Bulgaria”. They have been used for the preparation of the maps. The project was implemented by Green Balkans Society in 2005–2007 and the results were provided by its leader Simeon Marin.

References. Only the most important literature sources have been cited. They contain information about the vegetation, flora and fauna of the habitat at national level or include a detailed description of the habitat locality.

Rossen Tzonev, Chavdar Gussev, Veska Roussakova, Marius Dimitrov