According to the Regulation on the Ecological Network, the entire island of Lokrum, including the belt of sea of about 150 meters from the coast, is also an area of the Natura 2000 ecological network (HR4000017 Lokrum) – a conservation area of importance for species and habitat types (POVS) for a total of eight habitat types.
1. POSIDONIA BEDS (Posidonion oceanicae)
POSIDONIA OCEANICA (L.) DELILE is a seagrass species that is endemic to the Mediterranean Sea. Posidonia grows in clean and clear waters, in the infralittoral zone from the surface of the sea to a depth of 40 m, and tolerates well exposure to waves and temperature variations but not reduced salinity and eutrophication. Posidonia beds are important for life in the sea as they are the habitat of many living organisms that find food and shelter in its meadows. It is threatened by many human activities (anchoring, pollution, etc.) and is particularly vulnerable because the restoration of potentially damaged habitats would take decades. Characteristic species for Posidonia beds are: the warty venus (Venus verrucosa), the Mediterranean red sea star (Echinaster sepositus), the seagrass asterina, (Asterina pancerii), the cotton-spinner (Holothuria tubulosa), the noble pen shell (Pinna nobilis) – strictly protected species, fish Sarpa salpa, Symphodus ocellatus and Syphodus rostratus.
2. REEFS
Reefs are the most heterogeneous habitat type, encompassing habitats on a hard substrate from the surface of the sea to the bathyal, and can thus be of biogenic concretion or geogenic origin. Habitats can come into contact with terrestrial habitats on seaside rocks covered in vegetation (rocks and steeps of the Mediterranean coast overgrown with endemic species of Limonium ssp.), Posidonia beds and sea caves. Since they are present in a narrow strip along the coast, they are endangered due to exposure to human activities such as construction and sea-filling, concreting and levelling of the naturally uneven rocky shore. Characteristic species for this habitat type are sea snails (Melarhaphe nerioides), the beadlet anemone (Actinia equina), and limpets (Patella ssp.).
3. ROCKS AND STEEPS (CLIFFS) OF THE MEDITERRANEAN COAST OVERGROWN WITH THE ENDEMIC SPECIES Limonium ssp.
The steeps and rocky shores of the island of Lokrum are overgrown with halophytic vegetation. The community of “grebenjača savitljive mrižice“ (As. Limonietum anfracti Ilijanić 1982) is significant for Lokrum. This relatively rare and endemic community was first described on Lokrum, and is present in southern Dalmatia on Mljet, Lokrum, Elafiti Islands, and other islands and islets of the Dubrovnik coast as well as in the coastal belt of Dubrovnik littoral. A typical species of this community is “savitljiva mrežica” – Limonium dictyophorum (syn. Limonium anfractum), while rock samphire (Crithmum maritimum), Grey Bird's-foot-trefoil (Lotus cystoides), maidenstears (Silene vulgaris ssp. Angustifolia) and others are also present. On Lokrum, this community grows in the coastal belt along the entire coastline, but is less present on the western side of the island in the area where the cliffs are located, and only in a relatively narrow strip.
4. CARBONATE ROCKS WITH CHASMOPHYTIC VEGETATION
A vegetation habitat that develops in the cracks of dry limestone rocks and as fragmented in the walls of old buildings. Of the communities of this habitat on Lokrum, there is a significant community of “gorostasna šašika“ and “kalabrijska pogančina“ (Seslerio - Putorietum calabricae H-ić 1962) in the fortress walls, along with other characteristic species: the stinking madder (Putoria calabrica), the shortpod mustard (Brassica incana), “bjelušina” (Inula verbascifolia), etc. On Lokrum Island we can find it in a relatively small area on the rocks on the western side of the island, at heights that are beyond the reach of spray of waves during bad weather.
5. EUMEDITERRANEAN GRASSLANDS (Thero – Brachypodietea)
Eumediterranean grasslands are low grasslands composed of annual plants that generally complete their life cycle before summer droughts. The most significant community of Eumediterranean grasslands on Lokrum is the grassland of the yellow serradella and the rattail fescue (Ornithopodi - Vulpietum H-ić 1960), which was also described for the first time on Lokrum (locus classicus) with a rich composition of – “brčak” (Vulpia ligustica), the bird's-foot (Ornithopus compressus), the French oat grass (Gaudinia fragilis), the common cottonrose (Filago vulgaris), etc.
6. EVERGREEN FORESTS OF THE HOLM OAK (Quercus ilex)
Today, Mediterranean forests dominated by the holm oak (holly oak) rarely develop into high forests, but are mostly degraded to the macchia stage. From the mentioned forests, on Lokrum are present:
- the holm oak and flowering ash forest (Fraxino orni – Quercetum ilicis) with the most significant species being: the holm oak (Quercus ilex), the flowering ash (Fraxinus ornus), the laurustine (Viburnum tinus), the tree heath (Erica arborea), the Irish strawberry tree (Arbutus unedo), the green olive tree (Phillirea latifolia), etc. On the island of Lokrum we find this community in the interior of the southern part of the island and can recognize it by the flowering ash trees which distinguish it from the other forest communities on the island,
- the holm oak forest with myrtle (Myrto – Quercetum ilicis) – a holm oak forest in its degradation stage of macchia, a dense, almost impassable community in which, besides trees and shrubs, vines are particularly present, and the layer of ground vegetation is almost non-existent. Besides the holm oak (Quercus ilex), the mastic tree (Pistacia lentiscus) also grows here as well as the common myrtle (Myrtus communis), the large-fruited juniper (Juniperus oxycedrus ssp. Macrocarpa), the strawberry tree (Arbutus unedo), the tree heath (Erica arborea), the evergreen honeysuckle (Lonicera implexa), the rough bindweed (Smilax aspera), the wild asparagus (Asparagus acutifolius), and other evergreens. On Lokrum, this community is copiously present in the form of forests and macchia.
7. MEDITERRANEAN FORESTS OF ENDEMIC PINES
The habitat includes Aleppo pine or stone pine forests (whose forests are present only on the island of Mljet). Of the Mediterranean forests of Aleppo pine, on Lokrum are significant the following:
- the Aleppo pine and holm oak forest (Querco ilici–Pinetum halepensis) belongs to the most endangered forests of the Mediterranean – mostly due to fires and prejudices of the local population about the harmfulness of the Aleppo pine. These stands have a great social, aesthetic and ecological role. The main species of the community is the Aleppo pine (Pinus halepensis), in the layer of shrubs and low trees are the holm oak (Quercus ilex), the mastic tree (Pistacia lentiscus), the lauristine (Viburnum tinus), the common myrtle (Myrtus communis), the rough bindweed (Smilax aspera), the wild asparagus (Asparagus acutifolius), the butcher's-broom (Ruscus aculeatus), and other herbaceous and woody species. On Lokrum, this community is copiously present in the interior of the southern and central part of the island and on the eastern and northern slopes of the northern part of the island. The community is present in the coastal strip of the island, from the southeast across the south to the southwest coast of the island,
8. SUBMERGED OR PARTIALLY SUBMERGED SEA CAVES
Due to karst features along the Croatian Adriatic coast, sea caves are numerous. These are caves or holes with underground lakes or smaller aquatic habitats, usually with limited exposure to external climatic conditions, and more or less connected to the sea. There is also a significant influence from terrestrial habitats. On Lokrum are located, as part of this habitat type, Vela špilja and Mala špilja, and on the southern part of the island is Mrtvo more – a former cave whose ceiling collapsed at one point, and which today has the shape of a small “lake” connected to the outside sea by a canal about 15 m long.
FAUNA
Bats, and thus their colonies, are protected by national and EU legislation. The island of Lokrum is an ideal habitat for a number of species of bats, given the wealth of forest habitats, three open water areas, numerous natural and artificial shelters (buildings), as well as the silence and lack of lighting and human activities during the night. For most species of bats, Lokrum is an oasis in Croatia, which is otherwise characterized by urbanization, heavy traffic, artificial lighting at night and noise created by humans. A total of 11 of the 33 bat species recorded in Croatia were found on Lokrum, which is an extremely high biodiversity of bats for an island area of only 0.7 km². Studies have confirmed the presence of maternity colonies of the Kolombatovic's long-eared bat (Pl. kolombatovici) and the lesser horseshoe bat (Rhinolophus hipposideros) in the attics of the Benedictine monastery, while also present are species such as the Savi's pipistrelle (Hypsugo savii), the common bent-wing bat (Miniopterus schreibersii), the whiskered bat (Myotis mystacinus/aurascens), the Natterer's bat (Myotis nattereri), the common noctule (Nyctalus noctula), the Kuhl's pipistrelle (Pipistrellus kuhlii), the Nathusius's pipistrelle (Pipistrellus nathusii), the greater horseshoe bat (Rhinolophus ferrumequinum) and the European free-tailed bat (Tadarida teniotis).
On Lokrum Island, 52 species of birds have been recorded, of which 12 are resident nesting birds: the Eurasian sparrowhawk (Accipiter nisus), the Eurasian eagle-owl (Bubo bubo), the European greenfinch (Chloris chloris), the rock dove (Columba livia), the hooded crow (Corvus cornix), the chaffinch (Fringilla coelebs), the Eurasian wryneck (Jynx torquilla), the white wagtail (Motacilla alba), an allochthonous species – the common peafowl (Pavo cristatus), the Eurasian blackcap (Sylvia atricapilla), the Sardinian warbler (Sylvia melanocephala) and the Eurasian blackbird (Turdus merula). Of migratory nesting birds, species such as the common swift (Apus apus), the pallid swift (Apus pallidus), the barn swallow (Hirundo rustica), the nightingale (Luscinia megarhynchos) and the Eurasian scops owl (Otus scops) have been recorded. Wintering birds have also been recorded, such as the northern goshawk (Accipiter gentilis), the common buzzard (Buteo buteo), the European robin (Erithacus rubecula), and others, as well as passage migrants – the squacco heron (Ardeola ralloides), the European snake-eagle (Circaetus gallicus), the common cuckoo (Cuculus canorus) and others, in addition to two migration birds – the European honey buzzard (Pernis apivorus) and the western rock nuthatch (Sitta neumayer).
Harmless snakes are present on Lokrum: the slender whip snake (Platyceps najadum) and the Balkan whip snake (Hierophis gemonensis), which are, however, very rarely seen. There are also species such as Hermann's tortoise (Testudo hermanni), the Balkan green lizard (Lacerta trilineata) and the Mediterranean house gecko (Hemidactylus turcicus).
On Lokrum Island, 212 species of diurnal and nocturnal butterflies have been recorded, of which 18 belong to diurnal butterflies. All recorded species are typical of the southern Adriatic islands. Forested Lokrum is most suitable for forest species and forest edge species such as the speckled wood (lugara (Pararge aegeria), the eastern rock grayling (Hipparchia syriaca) and the southern white admiral (Limenitis reducta). These three species are very common and widespread on the island. In the coastal areas we also find the two-tailed pasha (Charaxes jasius), one of our largest and most colourful diurnal butterflies. Of the Mediterranean species, the island is inhabited by the Cleopatra (Gonepteryx cleopatra), the pea blue (Lampides boeticus) and the mountain small white (Pieris ergane). We can also meet the occasional common yellow swallowtail (Papilio machaon), the clouded yellow (Colias croceus), the red admiral (Vanessa atalanta) and the painted lady (Vanessa cardui). The presence of the purple hairstreak (Favonius quercus) is significant, given that there are only a few recent finds of this species in the Dubrovnik-Neretva County.
On Lokrum Island, 72 species of beetles have been recorded, most of which are ladybugs (Coccinellidae), leaf beetles (Chrysomelidae) and long-horned beetles (Cerambycidae).
Of the Orthoptera on Lokrum, a total of 16 species have been found so far, of which just 7 live only outside the forests, while for four of the species this is the first time they were recorded in the area of the City of Dubrovnik. Four species of grasshoppers are also found (Acrotylus patruelis, Oedipoda caerulescens, Pezotettix giornae and Chorthippus bornhalmi) (Tvrtković 2016).
