Terkos Basin This is an IBA in Danger! 

Year of compilation: 2016

Site description (baseline)
The Terkos-Kasatura Kıyılan (Coastline) IPA comprises a complex of aquatic and swamp communities, assoriated with Terkos Lake (one of İstanbul's most important drinking water reservoirs) and sand dune habitats, set in a hinterland of grassland, heath and coppice forest habitats. The coppice forest habitats are probably the largest surviving area of actively worked coppice (in good condition) in Turkey, and support what is believed to be one of the largest surviving traditional charcoal production enterprises in Europe. The site's flora is exceptionally rich: 575 vascular plant taxa have been recorded, and the floras of the freshwater and sand dune ecosystems are amongst the richest in Turkey. Over 73 local and nationally rare plant spedes occur, including 10 spedes listed on Appendix I of the Bern Convention, plus a further 8 Globally Threatened spedes. Amongst the most important wetland spedes are Stratiotes aloides, Vallisneria spiralis and Trapa natans, whilst notable sand dune spedes include Aurinia uechtritziana, Festuca beckeri, Isatis arenaria, Linum tauricum ssp. bosphori, Silene sangaria and Verbascum degenii. Overall, the IPA can be regarded as one of the most important areas of European dune, grassland, forest and wetland vegetation in Turkey, and is perhaps the single most important complex of habitats for nature conservation in Turkish Thrace.
The prindple threats to the site arise from water manipulation schemes (since c. 1995 the lake water has been supplemented with water from seven other catchments), afforestation of grassland and dune habitats, and construction of secondary homes (Byfield et al. 2010)

The Terkos Basin, which includes the Terkos Lake, is one of Istanbul's oldest water resources. The Basin is located to the north of Çatalca Peninsula which is mostly within the boundaries of the province of İstanbul. The KBA continues north within the boundaries of the Kırklareli province, until the Kıyıköy coasts. The Basin is surrounded by the Istranca Mountains to the west and the Terkos Lake to the east. The majority of the area is covered with forests (Eken et al. 2006).

The Terkos-Kasatura Kıyıları (Coastline) comprises a substantial tract of coastline, together with its hinterland of forest, associated with the ridge of hills that runs parallel to, and between 10 and 15 km. inland of, the Black Sea. The main peaks of the hills rise to between 300 and 400 m., and since their geology is largely acidic, they are today still almost entirely clothed with semi-natural vegetation. Whilst much of the landscape is composed of coppice forest, a series of exceptional open grass, heath and wetland habitats - most notably those associated with Terkos Gölü - add considerably to the interest of this mosaic of habitats.

The prindpal wetland within the site is Terkos Gölü (lake) and its assodated habitats. The lake itself was formed where the exit to the Black Sea of the Istranca (Binkılıç or Kanlıdere) Deresi and other smaller streams was blocked by a sand bar approximately 3 km. long and averaging 2 km. in width. The lake averages 2 to 4 m. in depth (up to a max. of 13 m.), and covers an area approximately 2500 ha. in extent. Its naturally forested catchment covers an area in the order of 600 km2 and accordingly the lake in freshwater, despite its close proximity to the sea. The forested nature of its catchment also ensures a high water quality within the lake, which is of considerable economic importance since this is one of İstanbul's prindpal drinking water reservoirs (Byfield et al. 2010). 


Key biodiversity
There are 17 plant taxa living in KBA. Some of them are breeding waterfowls such as: Ferruginous duck (Aythya nyroca), Lesser spotted eagle (Aquila pomarina), Little bittern (Ixobrychus minutus), and Squacco heron (Ardeola ralloides) are some of them. Most of them are endangered: Red breasted goose (Branta ruficollis), White-tailed eagle (Haliaeetus albicilla) and Greater spotted eagle (Aquila clanga). The lake hosts more than ten thousands birds in the same time in winter.
Leading important mammal species in KBA are Long-fingered bat (Myotis capaccinii), Mediterranean horseshoe bat (Rhinolophus euryale), Lesser mole rat (Nannospalax leucodon), and European ground squirrel (Spermophilus citellus). There is also Eurasian otter (lutra lutra) around Motor Deresi. Terkos lake is also important for amphibians such as: European fire-bellied toad (Bombina bombina) and southern crested newt (Triturus karelinii). KBA is also important for a kind of damselfly, Somatochlora borisii which is narrow expanded. (Magnin and Yarar, 1997). 
GLOBAL CONSERVATION CONCERN SPP. [8 TAXA] Asperula littoralis [END, V*], Centaurea hermannii [END, V], C.kilaea [END, V], Cirsium polycephalum [END, V*], Isatis arenaria [END, E*], Linum tauricum ssp. bosphori [END, E*], Silene sangaria [END, E], Verbascum degenii [END, E]
Aurinia uechtritziana [V], Cirsium baytopae [END, R], Crocus flavus ssp. dissectus [END, R], C.pestalozzae [END, R], Cyclamen coum [n/l], Erysimum sorgerae [END,n/l**], Himantoglossum caprinum [n/l], Peucedanum obtusifolium [END, n/l], Salvinia natans [R], Trapa natans [n/l], Vaccinium arctostaphylos [n/l], Veronica turrilliana [R]
Anemone blanda [V] , A. coronaria [V], Anthemis tinctoria var. euxina [n/l*], Atriplexpatula [K], Baldellia ranunculoides [R], Centaurea inermis [R], Chenopodium opulifolium [R], Cicendia filiformis [n/l], Comandra umbellata ssp. elegans [R], Corrigiola litoralis [V], Crambe maritima [E], Crinitaria linosyris [R], Cyperus hamulosus [n/l], C. odoratus [n/l], Elatine alsinastrum [n/l], Erysimum diffusum [K], Festuca beckeri [R], Fraxinus pattisae [V], Galanthus nivalis [V], Jasione montana [R], Juncus pygmaeus [RL Jurinea kilaea [R], J. macrocalathia [R], Leucojum aestivum [V], Lilium martagon [E], Linaria odora [V], Linum hirsutum ssp. byzantinum [V],Lythrum borysthenicum [I], L.portula [I], Malva pusilla [K], Montia minor [K], Najas marina ssp. marina [R], Nectaroscordum siculum ssp. bulgaricum [R], Ophrys bombyliflora [R], O.bucephala [n/l], Orchis papilionacea ssp. papilionacea [n/l], Pancratium maritimum [V], Parapholis filiformis [R], Paronychia echinulata [V], Polygonatum hirtum [R], Polygonum mesembricum [V], Radiola linoides [n/l], Ranunculus lingua [R], R. thracicus [R], Ruscus aculeatus ssp. angustifolius [V], Stratiotes aloides [R], Thelypteris palustris [R], Tilia cordata [R], Tournefortia sibirica [R], Vallisneria spiralis [R], Verbascum bugulifolium [n/l], Veronica scutellata [R], Viola canina [K] 
(Byfield et al., 2010).

Habitat and land use
The KBA contains a rich flora with its forests, heathland, freshwater and sand dune ecosystems. The KBA has a dominant forest flora and is also home to the largest swamp forest in Turkey. Heathland can be found in the dry parts of the forests and on the southem slopes. Being unpolluted, the lake has a well preserved natural life in the basin with a rich wetland ecosystem containing rare plant species. The Danamandıra Lakes, located in the middle of the KBA, includes heathland and swamp forests together with a rare acidic wetland (Eken et al. 2006).

The coppice forest habitats are largely composed of mixed Quercus, with some areas of Fagus orientalis and Tilia argentea in cooler areas. In many areas mature, pollarded T. argentea are a characteristic feature of shaded gullies, left (presumably) to supply lime-flower tea. From afar, the coppice forests look extremely uniform, but phytosociologically they are highly varied. Thus, to the south of the main ridge of hills (between Saray and Subaşı) much of the forests lie over poorly drained add clays, which take on a somewhat heathy nature after coppicing, with abundant Arbutus unedo and Erica arborea. This habitat supports the bulk of the world population of the Globally Threatened Centaurea hermannii. In contrast, on the steep north faring slopes of the higher hills (particularly close to Çilingoz), Fagus orientalis is codominant, and the flora is par¬ticularly rich (for western Turkey) in Euxine members of the flora, e.g. Ilex colchica, Laurocerasus offidnalis, Rhododendron ponticum and Vaccinium arctostaphylos. In general, the woodland is cut on a twenty year coppice cycle, either to provide fuelwood for local villages or for use in the production of charcoal. The scale of these coppice forests is vast. The forests within the IPA representthe eastern sector of an almost uninterrupted mantle of sustainable cop¬pice that runs for over 100 km. to the Bulgarian border (albeit with substantial areas of high forest in the Istranca Dağları). They probably represent the single largest continuous block of active coppice for¬est in Turkey today.
The forest areas contain a number of features of exceptional archaeological value, dating back to Byzantine times. Most notable are the Long Wall of Anastasius, an 11 m. high fortified wall, at 51 km. in length the second longest fortified structure dat¬ing from antiguity in Europe; and the 271 km. long Istranca Water Supply Line, the longest Roman water supply line on earth, boasting the remains of over 40 aqueducts.
Heatland habitats occur within the forest areas, particularly associated with drier hilltops, overlying wet acid clays, and south facing slopes. These are fragmentary in nature, and do not cover the extensive areas as seen to the east of the Bosphorus (Ömerli Havzası, IPA No. 12). They are nevertheless of considerable importance. In the area around Çilingoz and Kasatura the infertile heathlands support substantial stands of native Black Pine (Pinus nigro ssp. pattasiana), presumably able to establish through the lack of competition from faster growing beech and oak coppice stools. These represent one of the few natural stands of this pine in European Turkey, and one of only a handful of places in Turkey where Black Pine occurs at sea level. Other rare species within the heathland areas include Comandra umbellata ssp. elegans and Crocus flavus ssp. dissectus in dry heath, and Cicendia filiformis, Crocus pestalozzae, Isoetes spp., and Radiola linoides within short I seasonally-wet heath grassland.

A few Limited areas of limestone occur within the IPA giving rise to a series of calcareous grassland habitats. The two largest areas comprise a region of harder limestone with numerous swallow holes in the Gümüşpınar/Pınarca area, supporting rather short, extensively grazed grassland amongst scrub; and some fine Ouniper grasslands, in relatively deeply incised dry valleys, overlying the Gürpınar Formation, in the area around Deliyunus. The latter include important populations of national rarities such as Linum hirsutum ssp. byzantinum and Veronica turrilliana. They are also notably rich in orchids, with at least 18 species present, including relatively rare spedes as Ophrys bombyliflora, the newly described 0. bucephala, and the hybrid Orchis purpurea x simia. The valley bottoms within the chalk district still support grazed water meadows over calcareous loam: Orchis laxiflora and Leucojum aestivum are a distinctive feature of these meadows, together with more localised populations of Crocus biflorus ssp. biflorus and Galarithus nivalis x plicatus ssp. byzantinus

Throughout the forest and heathland zone a series of seasonally flooded pools and trackways, overlying acid clays and typically heavily stock grazed (in this case largely by water buffalo), are of importance for a range of rare and often ephemeral species including Baldellia ranunculoides, Elatine abinastrum, Juncus pygmaeus, Merıtha pulegium, Pulicaria vulgaris, Ranunculus ophioglossifolius, R. thracicus and Veronica scutellata. Many of these species are declining fast over much of Europe through cessation of extensive grazing and infilling. At Danamandıra, two shallow add meres over incipient peat are perhaps the largest and finest examples of their kind in Turkey. No more than one metre in depth, they support an open emergent vegetation with Carexelata, Phragmites australis and Schoenoplectus lacustris, whilst margins support further localised ephemerals such as Corrigola litoralis and Lythrum borysthenicum. Other fine examples of add pools exist in the Çayırdere-Sayalar area and around Sinekli 
The aquatic vegetation within the lake represents one of the richest of any freshwater site in Turkey. The submerged flora includes Ceratophyllum demersum, Myriophyllum spicatum, M. vertidllatum, Najas marina, N. minor, Potamogeton crispus, P. lucens, P. perfoliatus, P. trichoides, Stratiotes aloides (in its only Turkish locality) Utricularia australis and Vallisneria spiralis (in fewer than five Turkish localities). A rich floating vegetation includes Hydrocharis morsus-ranae, Lemna spp., Nupharlutea, Polygonum amphibium, Salvinia natans, Trapa natans and a notable abundance of Nymphaea alba.
Much of the emergent zone of the lake is dominated by beds of Phragmites australis, Typha angustifolia, T. latifolia, T. laxmanrıii and Schoerıopiectus lacustris ssp. lacustris, which reach their maximum extent in bays and at the head of the lake's arms. Lower growing and more species-rich areas of emergent vegetation, swamp and grazed lake margin include a range of more localised species such as Baldellia ranunculoides, Butomus umbellatus, Carex pseudocyperus, Cladium mariscus, Corrigiola litoralis, Cyperus hamulosus, C. odoratus, Eguisetum, hyemale, Oenanthe aquatica, Ranunculus lingua and Thelypteris palustris.

Flooded forest, dominated by Fraxinus angustifolia ssp. oxycarpa and Carex riparia, has developed on alluvium in a number of the wider valleys adjacent to the lake, notably in the lower reaches of the Istranca Deresi (south and west of Ormanlı) and in the Sinanköprü Deresi (south-west of Deliyunus). The margins of such forests are of important for substantial populations of the snowdrop Galanthus nivalis x plicatus ssp. byzantinus (G. x valentinei nothossp. subplicatus).

Sand dune vegetation has formed on the bar separating Terkos Gölü from the Black Sea, and at a number of other locations where the strong northerly winds (the 'Poyraz') has deposited wind-blown sand up cliff slopes and in cliff gullies (notably at Ömerdayı Tepesi, north of Ormanlı and at Kasatura). The dunes here cover a total of approximately 1500 ha. Despite an extensive and highly destructive afforestation programme over much of the dunes, the dune vegetation and flora is of exceptional importance. The flora includes the highest number of nationally rare plant spedes of any dune system on the Black Sea coast, and includes nationally and internationally important populations of Alyssum stribrnyi, Anthemis tinctoria ssp. euxina, Artemisia marschalliana, Aurinia uechtritziana, Centaurea kilaea, Festuca beckeri, Isatis arenaria, Jasione montana, Jurinea kilaea, Linaria odora, Linum tauricum ssp. bosphori, Matthiola fruticulosa, Peucedanum obtusifolium, Silene dichotoma ssp. euxina, Silene sangaria and Verbascum degenii (Byfield et al. 2010). 

Pressure/threats to key biodiversity
Dam construction. Secondary housing constructions, illegal hunting (Eken et al. 2006)
Since the end of the nineteenth century, Terkos Lake has been utilised as one of İstanbul's most important drinking water reservoirs, and accordingly this has afforded some protection to the lake and surrounding habitats. Early manipulation of the water level of the lake (including raising the level and digging a new cut to the sea) have apparently little affected the vegetation and flora. However during the mid 1990s the Istranca Water Supply Scheme has supplemented the quantity of water from the lake's natural catchment with that of water from a series of rivers to the west. As of 2000, six out of seven proposed dams have been completed
on streams as far west as Kıyıköy (Midye), with proposals to intercept further streams as far west as Demirköy (close to the Turkish-Bulgarian border). The effect of altered water levels (they have appar¬ently been significantly raised), and changes in
water chemistry on the vegetation and flora is not yet known. However, anecdotal evidence suggests that the water clarity in 1998 was reduced compared with that of 1994, and that populations of Stratiotes aloides had declined dramatically. Monitoring of this situation is essential.

Afforestation of the sand dunes at Terkos has been undertaken to control erosion in the sand dune zone, deemed to represent a considerable threatto the water resources of the adjacent Terkos Gölü. Two small areas of the dunes were afforested by the French in 1885-1887, but the vast bulk of the dunes were subsequent afforested by the Turkish Ministry of Forestry in the 1960s. At this time large scale afforestation of sand dunes had not been undertaken in Turkey, so the Terkos dunes, together with the Side-Sorkun dunes at Manavgat (on the Mediterranean coast) were chosen as experimental pilot sites. At Terkos, Acer negundo, Alnus barbata, Cupressus sempervirens var. horizontalis, Fraxınus oxycarpa, Pinus brutia, P. maritima, P.pinea, Platanus ocddentalis, Populus euroamericana and Robinia pseudacacia were used in the experiments. The survival percentages were in most cases high, and today much of the dunes are clothed in dense pine and false acacia forest. The afforestation programme has severely damaged or destroyed consid¬erable areas of sand dune vegetation, and will ultimately result in the loss of much of the sand dune interest within the site, including possible extinction (within the site) of Globally Threatened species
such as Isatis arenana and Linum tauricum ssp. bosphori. Introduced Cytisus scoparius [apparently not native to Turkey, but used here and at Kilyos Dunes (IPA No.8) as a forest nurse/shetter crop] is now rapidly naturalising in open habitats on add soils (e.g. dune, heathy maquis): it should be controlled. Smaller scale afforestation programmes have also taken place within open limestone grassland and heathland areas within the IPA, some undertaken for environmental purposes by environmental NGOs. Such schemes have caused considerable loss of the Juniper Grasslands, and threaten rare species such as Linum hirsutum ssp. byzantinum and a range of orchid species.
Demand for high quality housing in rural areas poses another growing threat. One major development (the Durusu Park development at Deliyunus, started in the mid 1990s) will cause severe damage to one of the largest remaining complexes of lime¬stone grassland within the site, and may set a precedent for further development close to the edge of Terkos Gölü.
Proposals to drain the lakes at Danamandıra in order to facilitate peat extraction were stopped following a campaign by locals and NGOs such as DHKD. Today the lakes receive protection as a Natural Heritage Area.
Extensive gravel extraction in the Sinekli area is destroying substantial areas of heathland and coppice on the gravel capped hills in the area (Byfield et al. 2010).

Protected areas
Limited parts of the Terkos to Kasatura Kıyıları receive formal protection. Kasatura Bay, together with the Coastal zone to the west was declared a Strict Nature Reserve (Kasatura Körfezi, 329 ha.) on 18 April 1987, to protect the stands of Coastal Black Pine (Pinus nigra ssp. pallasiana). The Danamandıra lakes are was declared a Natural Heritage Area (Class I & II) on 14 October 1999. The lower reaches of Yalıköy (Çilingoz) Valley have been declared a Permanent WiIdlife Reserve.
Terkos Gölü was formerly identified as an Important Bird Area by DHKD and BirdLife International, but later studies suggested that the site had lost the bulk of its interests through over-hunting and high levels of human disturbance. Recent ornithological surveys of the lake suggest that the lake retains sufficient ornithological interest to warrant its reinstatement as an IBA.
Bern Convention Appendix I species: Aurinia uechtritziana, Centaurea hermannii, Cyclamen coum, Himantoglossum caprinum, Salvinia natans, Silene sangaria, Trapa natans, Vaccinium arctostaphylos, Verbascum degenii, Veronica turrilliana.
Bern Convention Endangered Natural Habitats: 16.2113 - Pontic embryonic dunes, 16.2124 - Pontic white dunes, 16.22B11 - South-western Pontic fixed dunes, 16.27 - Dune juniper thickets and woods 16.31 - Dune-slack pools, 22.3233 - Wet ground dwaif herbs, 22.412 - Frogbit rafts, 22.413 - Water-soldier rafts, 22.414 - Bladderwort colonies, 22.415 - Salvinia covers, 34.3 - Dense perennial grasslands, 41.H1111 - Stranja beech- hornbeam-lime forests, 41.H1112 - Stranja beech- Quercus polycarpa [Q. petraea ssp. petraea] forests, 41.H21 - Thracian oak-hornbeam forests, 42.66 - Banat & Pallas' pine forests, 44.432 - Balkan ash- oak-alder forests (Byfield et al., 2010). 

Recommended citation
BirdLife International (2023) Important Bird Area factsheet: Terkos Basin. Downloaded from on 07/06/2023.