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EUProject funded by the
European Union

Water & nature in Croatia

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GEOLOGY - CARST

WETLANDS AND WATER

SEA

COAST

STATUS AND THREATS TO BIODIVERSITY


GEOLOGY- KARST

Adriatic coast reaches deeply into the lowlands where isolated karst patches can be found. The karst phenomena and forms have developed primarily in limestone. Croatia’s karst is characterized also by phenomena and forms in marl and sandstone rocks; or rather flysch series that are rare even in global proportions.

Karst rivers are rich in waterfalls and known for travertine phenomenon resulting in formation of characteristic geomorphologic forms. The penetration of water into stony substratum created caves, abysses, ice-pits including underground springs and estrevelle.

There are many threats to the karst rivers and underground waters as many of the sewers are discharged directly into the rivers. Caves are used as landfills and some are open to tourists without previously conducting biospeleological studies. Intensive agriculture is taking place in the areas where the ground allows for penetration of pesticides into underground rivers.


WETLANDS AND WATER

The longest Croatian rivers are Sava, Drava and Danube. The rivers flow into the Black Sea (62% catchment area) and the Adriatic (38% catchment area). The rivers belonging to the Black Sea catchments are lowland rivers along with numerous flood forests, grasslands, still backwaters with respective habitats can also be found.

The stretch of the river Drava between the mouth of Mura to Barc in Hungary forms steep landslide along its unfortified banks in which sand martins and kingfishers make their nests. In the sandbanks nesting birds such as small tern and little ringed plover can be found.

Due to their limestone base, rivers of the Adriatic catchment areas are short with frequent rapids and waterfalls, including sections of canyons. Numerous sink rivers flow through karst fields creating systems of underground water circulation, that are abundant with endemic fish species.

Lakes in Croatia are few but extremely valuable. The most well known are Plitvice Lakes that are formed by the Korana River flowing into 16 cascading lakes with numerous travertine downstream beds in a vivid biodynamic process. This is one of the most well known Croatian National Parks and the only one included on the UNESCO World Cultural and Natural Heritage list.

Vransko Lake near Pakostane is the greatest natural lake in Croatia with a surface area of 30.7km². Vransko lake on the island of Cres is much smaller but fairly deep (74m) and the Blue and Red lakes near Imotski are unique as well.

Croatia has an outstanding wealth of wetland habitats, four of which are by today included in the Ramsar list: Lonjsko Polje (50.5 hectares), Kopacki Rit (17.7 hectares), Lower Neretva (11.5 hectares), and Crna Mlaka fishponds (625 hectares).

Lonjsko Polje, in the central course of Sava, is a flood area with wide, wet flood forests of common oak, flood meadows and pastures and numerous backwaters.The habitats of numerous threatened species such as the white tailed eagle, lesser spotted eagle, black stork, spoon bill, white stork, spoonbill, white stork, blackbird and others are located here.

Kopacki Rit, situated where the Drava flows into Danube, is full of lakes, ponds and canals including fishponds. It is where the largest population of white eagles resides and the location for 90% of Croatia’s nesting white geese. It is also the only place in Croatia where the great cormorant is known to nest. Kopacki Rit is particularly valuable as a resting and feeding place for migratory waterfowl. During migration, flocks of several tens of thousands ducks and geese may be met there.

Another Ramsar site is the Neretva valley with wide wetland habitats including the largest and richest reed species in entire Mediterranean Croatia.

The biggest threat to the wetland areas are changes in water regulations specifically pollution from discharge and pesticides into the rivers. The construction of hydropower plants and formation of storage lakes have considerably affected the river flows and the karst. The wetlands are often drained and turned into marshy meadows and agricultural land.

SEA

Sea with a total surface of 138,595km². The Adriatic’s average depth is 173m. A depth exceeding 200m can be found around the island of Jabuka and in the southern Adriatic. The Adriatic, possessing low levels of nutritious salts, phosphorus and nitrogen in particular, is considered to be a sea that is low in productivity. However, considering the large number of endemic flora and fauna, the Adriatic stands out as a special biogeographical unit of the Mediterranean. Two areas are, in that respect, of particular importance - western Istria and parts of Kvarner, and around islands of Jabuka, Brusnik, Svetac, Vis and Plagruza. Some 6000-7000 plant ands animal species have been found in the Adriatic. A number of groups, especially invertebrates are insufficiently explored, making the basic data on their diversity, in most cases, not available.

The threats to the Adriatic are numerous especially to the shallow coastlines where uncontrolled development including backfilling, solid waste disposal and particularly discharge of unpurified waste water, both municipal and industrial is occurring. Excessive and uncontrolled fishing is adversely affecting various algae/ genus cystoseria including settlements of the endemic brown algae/Adriatic wrack that has almost completely disappeared from some polluted parts of the Adriatic (western Istria). In the shallow coastal parts particularly threatened are communities of photophilous algae and meadows of Posidonia oceanica, while in the deeper waters communities of detrial surfaces are in peril and also the communities of muddy surfaces due to excessive trawling.


COAST

Geological, climatic, physical and anthropological influences have combined to create unique coastal and marine biodiversity along the Croatian coastline. It is about 5,780 km long and the coastal area has some 1,750,000 inhabitants. There are over a thousand cliffs and islands, of which only 45 have approximately 126,000 permanent inhabitants.
The biogeographical position, limestone as a dominating geological base and distinctly karst relief, its indentation and the fact that it has been a sanctuary for plants and animals during the Ice Age, resulted in outstanding diversity and peculiarity.

The development of tourism is changing the native’s habits and lifestyles along the coast and on the islands. Population abandons traditional cattle breeding and agriculture. As a result, landscapes and ecosystems are being changed. Tourism is also putting a burden upon the limited water reserves on the islands. Sewage and industrial effluents are discharged untreated into the karst underground and sea. The pollution is of a local nature so far but with the anticipated development of tourism this, unless addressed, may result in far more serious damage. Excessive hunting and fishing, including the excessive use of pesticides have to a high degree affected a number of fauna.


STATUS AND THREATS TO BIODIVERSITY

Croatia is still regarded as a country with a high level of preserved nature and biodiversity. This notion implies a high level of protection which does not yet exist.

One of the major threats to biodiversity remains to be water pollution from urban agricultural and industrial sources. Only 40% of the population has access to sewage systems and only 12% of the water is being treated. Less than 5% receives secondary treatment.

Rivers are not managed for biodiversity. They are managed for flood control only. This is why flood control dams as well as electric hydropower plants continue to have an adverse effect on the ecosystems. Nevertheless, HEP (Croatia Electric Utility) announced the construction of two new hydro power plants including the one on the Dobra river near Lesce, a rich karst area.

For more information on Croatian biodiversity click here.

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Copyright © 2014 The European Union’s CARDS Programme for Croatia
last edited: Saturday, December 10, 2011