Strandzha Nature Park ( Priroden park Strandzha, also transliterated as Stranja Nature Park) is the largest protected area in Bulgaria spanning a territory of in the Strandzha Mountain in the extreme south-eastern corner of the country on the border with Turkey. It was established on 25 January 1995 to protect ecosystems and biodiversity of European importance, as well as the traditional cultural, historical and folklore heritage of the region. The altitude varies from on Gradishte Peak to at the Black Sea coast with average length of from west to east and from north to south.

The nature park is situated in Burgas Province with two towns, Malko Tarnovo and Ahtopol, and several villages within its territory. It includes five nature reserves: Silkosiya, Sredoka, Tisovitsa, Uzunbodzhak and Vitanovo. Silkosiya is the oldest one in Bulgaria, established in 1933, and Uzunbodzhak is included in the World Network of Biosphere Reserves under the UNESCO Man and Biosphere Programme. The whole territory is part of the network of nature protection areas of the European Union, Natura 2000.

Strandzha Nature Park falls within two terrestrial ecoregions of the Palearctic temperate broadleaf and mixed forest — the Balkan mixed forests and the Euxine-Colchic deciduous forests. Forests cover 80% of the park's area, with old-growth forest forming 30% of them. These woods are the last remaining temperate forests with evergreen laurel undergrowth in Europe. The park has the highest number of vertebrate species of all protected areas in Bulgaria, including 66 species of mammals, 269 species of birds, 24 species of reptiles, 10 species of amphibia and 41 species of freshwater fish, as well as 70 species of marine fish in the waters of the Black Sea. The invertebrate fauna is poorly researched and includes 84 Bulgarian endemic species, of which 4 are local, and 34 relict species.

The oldest traces of human habitation found in the territory of the park date from the Neolithic period in c. 6000 BC. By the mid-1st millennium BC Strandzha was inhabited by Thracian tribes, forming part of several Thracian kingdoms until the region was annexed by the Roman Empire in 45 AD. In the Middle Ages the area was contested between the Byzantine and the Bulgarian Empires until it was conquered by the Ottoman Turks in the late 14th century. After the Liberation of Bulgaria in 1878, Strandzha remained in the Ottoman Empire, which resulted in the 1903 Ilinden–Preobrazhenie Uprising by the local Bulgarian population. The region was liberated in 1912 during the First Balkan War. The rich history has left an important cultural heritage by several civilizations and folklore traditions unique for Bulgaria, such as Nestinarstvo that involves a barefoot dance on smouldering embers — a vestige from the pagan past. Traditional Strandzha wooden architecture from the mid-17th to the 19th century is preserved in the villages of Brashlyan and Kosti, as well as in the town of Malko Tarnovo.

Park administration

Strandzha Nature Park was established on 25 January 1995 to protect ecosystems and biodiversity, as well as the traditional cultural, historical and folklore heritage of the region. Before 1995 the protection of the region had been fragmented, consisting of isolated nature reserves and protected areas. The park is administered by a directorate based in Malko Tarnovo and subordinated to the Executive Forest Agency of the Ministry of Environment and Water of Bulgaria. The directorate implements the state policy for the management and control of the protected area, aiming at the long-term conservation of the unique nature and ensuring the sustainable social and economic development of the region. It monitors the management and conservation of the forests, game, and fish resources while encouraging tourism and environmental protection.

The park falls within the International Union for Conservation of Nature management category V (protected landscape/seascape). The whole territory of the park and the adjacent Black Sea waters are included in the European Union network of nature protection areas Natura 2000 under the code Strandzha BG0001007. Strandzha Nature Park is listed as an important bird and biodiversity area by BirdLife International. There are two information centres for visitors: in Malko Tarnovo and in Gramatikovo.

Geography

Overview

Strandzha Nature Park is situated entirely in Burgas Province within the territory of two municipalities, Malko Tarnovo and Tsarevo, in the extreme south-eastern corner of Bulgaria. This area includes the 7,000 inhabitants of 19 villages, and the towns of Malko Tarnovo and Ahtopol. Strandzha is the least populated region in Bulgaria with a population density of 10 people per km2. It is accessible through the I-9 first class road to the west and the III-9901 third class road to the east which serves the park coastline. The two roads are linked by the II-99 second class road. With an area of , or approximately 1% of the national territory, the park is the largest protected territory in Bulgaria. Due to the geographic location of Strandzha in the immediate vicinity of Asia, the park contains biodiversity of European importance as well as a unique historical heritage.

The vegetation of Strandzha evolved before the formation of the Bosphorus Strait when the whole southern Black Sea coast was linked and represents the westernmost extension of the Euxine-Colchic ecoregion. Because of the proximity of three seas, the Black Sea, the Marmara Sea and the Aegean Sea, Strandzha remained unaffected by the Quaternary glaciation and retained its mild and relatively humid climate. Under those conditions the region has preserved relict species from the Neogene.

Relief, geology and soils The relief of Strandzha is hilly, characterised by mild rolling ridges covered with dense woods. To the west the mountain is steeper and more rugged. Strandzha Nature Park has two clearly defined ridges — Rezovo ridge with its highest summit at Golyamo Gradishte peak at and Bosna ridge with Papia at ) forming the highest elevation. Approximately 38% of the park's territory has an altitude from , 60% from , and only 2% lies above . The mountain is an anticline with core layers formed by igneous and metamorphic rocks with Paleozoic origin and surface strata covered with Mesozoic sediments dating from the Triassic, Jurassic and Cretaceous periods. The anticline has an orientation from north-west to south-east. The river valleys are geologically young, formed during the Quaternary, and have gentle slopes and a slight inclination. In the western regions there is an extensive karst area with carbonate rocks spanning from the village of Varovnik to the town of Malko Tarnovo with ponors, caverns and caves.

The territory of Strandzha Nature Park falls within the Mediterranean soil area of Europe, characterised by wetter soils in comparison to the rest of Southern Europe. There are seven soil types in the park under the World Reference Base for Soil Resources soil classification — Fluvisols (4% of the park's area), Leptosols (10%), Cambisols (4%), Luvisols (46%), Planosols (20%), Alisols (11%) and Nitisols (5%). Strandzha is the only place in Bulgaria where Alisoils are found and the only place in Europe with Nitisols.

Climate The climate of Strandzha is influenced by the proximity of the Black, Marmara and Aegean seas which clearly distinguishes the local climate from that of the rest of Bulgaria. The region is among the warmest in the country with temperatures rarely falling below 0 °C in winter and rising above 24 °C in summer due to the cooling effect of the Black Sea. The average temperature drops with the rising elevation in the interior which creates conditions for more frequent and longer-lasting mists, heavier snowfall and earlier frosts. In winter frequent fogs lead to hard rime and the icing of the forests at altitudes above 50.

The winds are predominantly northern. Along the coastline the winds flow from the north in November – March, from the east in April – August and from the north-east in September – October. The sea breeze causes the high frequency of eastern winds in summer. In the interior the predominant wind direction is more varied with northern winds being the most frequent in January – March and in October.

The annual precipitation is high, reaching in some areas above . Along the coast rainfall is under the influence of the Mediterranean and is characterised with a winter maximum while the higher regions of Strandzha also have a second maximum in May – June as a result of the continental climate. In the interior rainfall is higher and influenced by the cold northern and north-eastern winds. There is no natural protection to the north which often results in abrupt temperature falls.

Strandzha has a significant potential for climate therapy. Due to the healthy climate along the coastline combined with sandy beaches, Ahtopol was designated a climatic sea resort of national importance and Sinemorets a climatic sea resort of local importance.

Rivers

Strandzha is criss-crossed by a dense network of deep ravines, streams and rivers. The rivers have a discharge maximum in winter, in November – December. With a total length of , the Veleka river is the longest and largest in Strandzha. Its upper course has a rocky bottom and many rapids. As the river flows through the karstic region of the mountain, its banks are steep with cliffs and precipices. After the village of Zvezdets, the river valley grows wider, the inclination decreases, the water flow slows and the river creates many meanders. In the lower course the river banks are flooded seasonally forming a wetland forest of alluvial longose groves. The Veleka is navigable in the first up from the river mouth.

The second longest river is the Rezovo river, at . It generally flows east and along most of its course forms the border between Bulgaria and Turkey. According to a hypothesis its etymology is linked to the mythological king Rhesus of Thrace. The banks of the river are covered with dense oak and beech forests. The Bulgarian bank is characterised with many cliff formations and caves. The Rezovo river is faster and colder than the Veleka and therefore has a larger trout population. The tributaries of the Veleka include the Mladezhka reka (), Mechi Dol (), Katun (), and the main tributary of the Rezovo river is the Delievska river ().

Protected areas

Strandzha Nature Park includes five nature reserves (Silkosiya, Sredoka, Tisovitsa, Uzunbodzhak and Vitanovo), eight natural landmarks, and 14 protected areas. Silkosiya is the first nature reserve in Bulgaria, established in 1933. It is situated to the north of Kosti and to the east of Balgari. It hosts 260 species of vascular plants and forests with average tree age of 120–130 years. Srednoka is situated in the lower course of the Mechi Dol river and is the only reserve in Strandzha with many meadows and open spaces. Tisovitsa is located in an area with a difficult access along the banks of the homonymous river and features archaeological sites from ancient Thrace. Uzunbodzhak is included in the World Network of Biosphere Reserves under the UNESCO Man and Biosphere Programme and is situated along the border with Turkey. Vitanovo is located on the main Rezovo ridge from Malko Tarnovo and from Brashlyan. Its altitude varies from 400 to 60, making vegetation different from that in the other reserves. Access to the reserves is restricted to research teams, with a few strictly defined tourist trails. Among the most significant protected areas are the Mouth of the Veleka river and Silistar. Silistar is situated on the Black Sea coast between the villages of Sinemorets and Rezovo and has the highest number of plant species per square kilometre in Bulgaria.

Biology

Flora