A River Rich in Biodiversity
Although rivers and lakes make up only 1% of the globe‘s land area, freshwater ecosystems host a rich diversity of landscapes and species.
The river dynamics of the Danube provide the basis for large range of habitats, from grassy plains and vast mountain ranges to lush wetlands and picturesque shores.
Where the river stream slows down, it loses its transporting capacity so that enormous quantities of gravel and sand settle on the bottom. The result of these deposits has been the formation of gravel islands. Many of these gravel banks and sandy islands continue to change shape and size due to annual floods, and such highly dynamic river habitats are some of the most endangered ecosystems.
Floodplain forests consist of a suite of plant species that tolerate, not just days, but weeks and even months of flooding. Floodplain forests provide excellent habitats, particularly for birds which use them as natural migratory corridors and nesting sites. They also play an important role in controlling downstream flooding by storing floodwaters and thereby dissipating the energy of the floodwaters.
Wetlands on the Lower River
Wetlands such as marshlands, deltas and lakeshores have numerous functions. They are valuable drinking water reserves for millions of people. They assist in reducing the impacts from floods and pollution. They also provide habitat for many species. However, 80% of the Danube's wetlands and floodplains were lost since the end of the 19th century, threatening species such as pelicans in the Danube Delta and beavers in the Upper Danube.
Flora and Fauna along the River
The Danube River Basin, including its tributaries, is home to around 2,000 plant and 5,000 animal species, including numerous endangered or nearly extinct species most of which are aquatic or water dependent.
Many mammals live along the shores of the Danube River and in the higher areas of the Danube Delta that cannot be reached by waters. Otters, minks, muskrats, foxes, black bears, wolves, polecats and hares are to be found along with tortoises, adders and colonies of snakes.
The highly diverse ornithological fauna of the Danube Basin and especially its delta, counts over 250 species of birds, like herons, eastern flossy ibises, small cormorants, golden eagles, black-winged eagles, avocets, shelldrakes, pelicans, reed nightingales, buntings, sea swallows, seagulls, fishing eagles, sea eagles, singing swans, plovers, polar grebes, half snipes, cranes, golden eagles, saker falcons, egrets, mute swans, large cormorants or Mandarin ducks.
Some 110 species of fish are to be found in the Danube River as well as in the hundreds of lakes, streams and channels in the delta: Sterlets, large beaks, great sturgeons, common sturgeons, sevrugas, mackerels, carps, sheat fish, perches, pikes, barbles, rapacious carps, aspruses, crucians, perches, breams, pikes and carps. The marine area in front of the delta shelters the Danube mackerel as well as five different species of sturgeons, which yield fine black roe, commonly known as caviar.
The basin of the Danube is also home to the longest marshland of the continent. Large stretches of reeds grow on the bed of Danube River. In fact the reedbeds in the Danube are among the largest in the world. Stippa grass can be found in the sandy areas on the banks of Danube. The Letea forest along the river contains several other plants. Many different species of water lilies grow in the river.
But aquatic biodiversity is facing an increasing risk. Invasive alien species are negatively impacting the natural fauna and flora in many rivers and lakes. Also, nutrients flowing off the land, as well as poor land use and land management like the straightening of rivers, detachment of floodplains and fragmentation of habitats through dams and weirs increase the degradation of habitats and loss of species.