River Nestos

River Nestos is the natural border between Macedonia and Thrace, and is one of the five longest rivers in Greece. The river is 234 km long, it rises at Rila mountain of Bulgaria and after 130 km in Greek soil, it flows into the Thracian Sea. It creates an environment of special interest, unique value and rare beauty where rare plants and endanger animals find shelter. The Aesthetic Forest which has developed along its Narrows, the Great Riparian Forest on its delta, the lagoons, the ponds, the wet meadows, the marshes and dunes at its estuary, characterize Nestos as an enormous natural and aesthetic, national capital.

The Narrows

River Nestos, on its course from Stavroupolis to Toxotes, crosses steep cliffs and erodes limestone and sedimentary rocks, thereby forming an impressive landscape. Its Narrows cover 2,380 ha and have been designated as an Aesthetic Forest. In its valley, approximately 500 plant species have been recorded. Ash trees, oriental planes, white poplars and crack willows, hornbeams, maples and Cornelian cherry dogwoods, elders, myrtles and many other species, compose a magical place and a perfect niche for threatened raptors, such as the golden eagle and rare mammals, such as the otter.

The Delta

The Nestos delta, that is the area between Toxotes Bridge and the Thracian Sea, where the alluvial deposits of the river have extended the land into the sea, has the shape of a fan. The bridge of Toxotes demarcates its top, whereas the coastal zone opposite to Thassos delimits its base. The east side of the delta reaches the lagoons of Avdira and the west side, those of Nea Karvali. Nine lagoons (Vassova, Erateino, Agiasma, Kokkala, Haidefto, Keramoti, Gefyraki, Palaias Koitis of Nestos and Monastiraki) are formed at the west side of the delta. These are surrounded by extensive salt marshes and are the most productive fish farms of Greece. The delta covers 55,000 ha and it is designed as Ramsar Site, Site of Community Importance of the NATURA 2000 Network, and a Special Protection Area.

The riparian forests

Riparian forests are a significant part of Greece’s natural heritage. They restrain catastrophic floods, filter a river from pollutants; they increase ground water recharge by decreasing water flow; they support biodiversity and create landscapes of outstanding aesthetic value.
Ecosystems of riparian forests are particularly sensitive to external, mainly human activity and they are today threatened. In the first half of the 20th century, 2/3 of Europe’s riparian forests were destroyed. River embankment, large flood-control and land reclamation works, but primarily removal of the natural vegetation in favour of agriculture are the reasons for what is left from the once glorious riparian forests usually in narrow strips along riverbanks. The largest riparian forest in Greece is that of Nestos.

The Great Forest

Known, in older times, as “Kotza Orman (Great Forest)”, the riparian forest of River Nestos was one of the largest of its type in Mediterranean area. In the early 20th century it covered 12,000 ha, which was almost 1/4 of the total delta. Since the 1920s, continuous clearance of the natural vegetation and the embankment of the river during the 1950s, impede the function of the deltaic system and caused the dramatic shrinkage of the previously superb forest. Today, although the riparian forest of Nestos has been restricted to merely 150 ha, all fragments along both sides of the river, it is still the largest of all natural riparian forests in Greece.

Vegetation of the riparian forest

The trees and shrubs growing in the riparian forest  of River Nestos are forming the following 11 types of vegetation:

  • Halophytic vegetation of sandy and coastal areas
  • Mediterranean temporary ponds
  • Riparian curtain-like forests with willows-poplars
  • Annual vegetation on silty river banks
  • Xeric meadows of Eastern Mediterranean
  • Mediterranean meadows with high grass and bulrush
  • Reedbeds
  • Residual alluvial forests
  • Mixed forests of oak, common elm and ash trees
  • Gallery forests with white willow and white poplar
  • Mediterranean riparian gallery forests

Halophytic vegetation of sandy and coastal areas

Formations of annual and perennial plants (e.g. glasswort, bulrush) colonising sandy and muddy areas, which are periodically flooded by the sea. They cover 2.75 ha and occur as patches.

Mediterranean temporary ponds

Amphibious dwarf halophytes grow in muddy soils or in soils flooded periodically. This vegetation is rare and occupies a very small surface area in the riparian forest of Nestos (0.05 hectares). It appears at various points along the river.

Riparian curtain-like forests with willows-poplars

On the riverbanks, starting from Toxotes dam to the estuary, where soil is sandy or sandy-clay, grasslands, bulrush formations and dense vegetation of white poplar and willows cover 690 ha.

Annual vegetation on silty river banks

Annual herbal plants, grow on muddy substrate, rich in nitrogen, which was generated by rather recent sedimentation. In the riparian forest of Nestos, they appear in patches and cover very small area.

Xeric meadows of Eastern Mediterranean

They develop on sandy islets in the river and in former riverbeds. They host endemic species; at wet locations, protected by intensive grazing, orchids may also be found. In the riparian forest of Nestos, they constitute approximately 60 ha and they grow on sand islets, at the northern part of the river.

Mediterranean meadows with high grass and bulrush

These are wet meadows with herbaceous plants, characterized by the occurrence of the tall bent grass species Erianthus ravennae (plum grass). They grow on clay or sandy-clay soils created by river sedimentation. In the riparian forest of Nestos, they cover 170 ha, along former riverbeds where salinity is high.

Reedbeds

Reedbeds of common reed and cattail develop on stagnant or slow-flowing waters, but also on very wet soils. In the riparian forest of Nestos, they stretch over an area of around 2.7 ha.

Alluvial alder forests

The alluvial alder forests grow in the river between the embankments. It is the most abundant vegetation type and covers around 300 ha. The dominant species is the common alder. Other species are the white poplar, the black poplar and the white willow.

Mixed forests with oak, elm and ash trees

They represent the largest and the most important vegetation type of the virgin riparian forest of Nestos of 66 ha. They are found out of the embankments, in the fenced part of the riparian forest. They develop on soils with low moisture, rarely flooding and very fertile. Dominant species are the pedunculate oak, the elm and two ash species, the common ash (or European ash) and the Pallis’ Ash. More species occurring here are the white poplar, the black poplar and the common alder. A distinctive feature of this vegetation type is its richness in climbing plants.

Galleries with white willow and white poplar

This vegetation is dominated by the white willow, the crack willow and the white poplar. They initially colonise the sandy depositions and the sandy islets in the river. It is tolerant to inundation by running water. Where the soil is not waterlogged throughout the year, ash trees appear. A distinctive feature of this vegetation type is its richness in climbing plants. In the riparian forest of Nestos, it occupies around 470 ha.

Mediterranean riparian gallery forests

This type of vegetation follows low halophytic vegetation towards the mainland. They are poor in species due to the adverse soil conditions (high water level or permanent inundation and high soil salinity). Dominant species are the tamarisk, the oleander and the vitex. In the riparian forest of Nestos they cover 15 ha.

Fauna of the riparian forest

In the past, the riparian forest of River Nestos provided food and shelter to wild animal which are now extinct, such as roe deer and deer. Despite its shrinkage, the forest continues to have the same role for a great number of other animals, many of which are rare or threatened.
Twenty one freshwater fish species occur in River Nestos (e.g. the Thracian barbel, the Vardar nase, the European chub, the Macedonian trout, the European bitterling, the belica, the European eel, the Strymon stone loach, the roach). Some of them are protected by the Hellenic and international legislation. Fourteen species are autochthonous and 6 are endemic (the spirlin, the European chub, the Vardar nase, the Thracian barbel, the Thracian spined loach and the belica). Three species had been transferred from other riverine systems and 4 other (the pumpkinseed, the stone moroko, the rainbow trout and the Eastern mosquito fish) are alien species.
In the lagoons and the estuary of the river 36 euryhaline and marine fish species have been identified. Ten of these species pass their whole life cycle in brackish water (e.g. the big-scale sand smelt, Black-striped pipefish, the South European toothcarp, the marble goby, the grass goby, the black goby), 17 are marine species that migrate in lagoons for food and shelter (e.g. the flat head grey mullet, the golden grey mullet, the thick lip mullet, the European sea bass, the gilthead sea bream, the striped seabream, the sharpsnout seabream) and the rest 9 species have been identified accidentally in the area.
In the riparian forest, around 150 bird species find refuge as well as foraging and wintering sites. Most of these species are protected by national, European and international legislation. A large number is included is included in the Red Data Book of Threatened Vertebrates of Greece and 103 species are listed under the Bern Convention, out of which 75 are included in the Directive 79/409/EEC. Elegant waders, such as the great egret, the little bittern and the glossy ibis, rare waterfowl such as the pygmy cormorant, the Eurasian spoonbill, the lesser white-fronted goose, the ferruginous duck and the black stork, but also threatened raptors such as the white-tailed eagle, the lesser spotted eagle, the long-legged buzzard, the imperial eagle, the grater spotted eagle and the osprey, as well as the nesting common pheasant, compose a unique ornithological community.
In the forest, a careful observer may find footprints of jackals, weasels and martens, badgers and wild cats. A total of 13 species of large mammals has been recorded. Six of these are listed in the Red Data Book of Threatened Vertebrates of Greece as endangered. The otter is included in Annex ΙΙ of the Directive 92/43/EEC as a priority species.
A large number of amphibians, reptiles and invertebrates interweave an environment of outstanding beauty and value. Common and rare frogs (e.g. the yellow-bellied toad, the common tree frog, the eastern spade foot toad, the common toad, the agile frog, the stream frog or Graecian frog), newts (great crested newt, smooth newt) and salamanders, several tortoise species (such as the Hermann’s tortoise, the Greek tortoise, the European pond terrapin and the Caspian turtle), snakes (e.g. the rat snake, the Montpellier Snake, the Dahl's Whip Snake, the nose-horned viper, the smooth snake, the grass snake, the dice snake) and lizards (e.g. the sand lizard, the green lizard, the Balkan wall lizard, the Mediterranean house Gecko, the Kotschy's gecko), rare insects, multi-coloured butterflies and beetles, create a multitudinous and humming community, in which each member has its own precious and irreplaceable role.