Negative factors
The nature around the Danube river is threatened by various negative effects.1. River regulation
During the last 200 years massive changes have been carried out on the targeted section of the Danube; the main aims of these interventions have been navigation and flood protection. The formerly continuous large inundation area has been divided by flood protection dykes into a small inundation area along the main river bed and into a large area without regular floods. In consequence, the area outside the new inundation zone is isolated from the direct impact of floods, whereas in the new inundation area this impact even increased. Simultaneously with the building of dykes, the banks of the main river course have been fortified with stones, large deposits of gravel in the river have been dredged and numerous river branches have been cut away from the river. In consequence the formerly flowing river branches have stagnant water during the majority of the year, the river banks are stable, no new branches are being created and due to natural sedimentation the number and area of river branches is slowly decreasing. The reduced dynamic processes lead to reduction of several habitat types, e.g. shallow water areas, gravel banks or steep river banks.
2. Changed water levels
As a consequence of various activities, the average water levels in some parts of the project site have been changed (decreased). Locally this has led to drying of the disturbed areas. The most serious impact was on the wettest floodplain forests and shallow water bodies, in several cases large river branches or wetlands remained without surface water. Complete local extinction of aquatic plants and animals followed here.
3. Changed water level dynamics
In several sections or areas of the project site, the water regime is artificially controlled. This controlled water regime is usually not suitable from the ecological point of view. The water management manipulation rules for the water level regulating objects tend to maintain one set water level (or several values, e.g. one water level during the vegetation period and another during the winter period). The formerly fluctuating water level of the inundation area is now strongly reduced, and in consequence, the area of temporary and shallow water has been heavily reduced. Another consequence of the artificially stable water levels is then the excessive development of water plants, and reduced area of shallow water without vegetation.
4. Lack of food for zoophagous bird species
Quantity of several groups of animals has been reduced heavily in some parts of the project site. To the most depressed animals belong fishes, amphibians and invertebrates inhabiting temporary water bodies. These groups of animals are important food basis for various bird species (e.g. Haliaeetus albicilla, Milvus migrans, Nycticorax nycticorax, Egretta garzetta, Ixobrychus minutus, Ardea purpurea). While some of the reasons of the lack of fish, amphibians and invertebrates are correlated with the previous treats and factors, there are also specific reasons: most important is the barrier effect that hinders the migration of fish.
5. Forest management
The forestry use of the project site has been very intensive during the last decades (and still is in several areas). In consequence, the amount of older trees is reduced, and, moreover in large areas there is a lack in native tree species. This has led to decrease of many species including the reduction of breeding possibilities of several bird species.
6. Abandonment of traditional use of meadows
Large proportion of the floodplain areas were traditionally used as pastures of domestic animals and mowed for obtaining hay. This long-term extensive land management has created specific rich mosaic of habitats. During the last decades majority of the extensive meadows has been abandoned and changed to arable land, hybrid-poplar plantings or just leaved unused. The unused former meadows are usually overgrown with several invasive neophytes (e.g. Solidago spp.).
7. Excessive disturbance of sensitive species
Some vertebrate species, mainly the large birds, are extremely sensitive to the presence of people in their nesting territories. Regularly, unsuccessful breeding or even complete leaving of the territory have been recorded as a consequence of disturbance by man. The project site is mostly a narrow belt along the Danube river, the width of this belt is usually just several hundred meters. Moreover, in the most parts of the project site, there is a rich network of forest roads, bridges and paths (often they are illegal!). Thus, the majority of the project site area is extremely accessible, even with cars. Although the disturbance is one of the main factors limiting the breeding of several endangered bird species (e.g. Haliaeetus albicilla, Ciconia nigra, Milvus migrans), this problem has never been under attention of nature conservancy authorities. Easy accessibility supports different illegal activities in the project sites such as poaching, shooting of birds, illegal net fishing, building of illegal camping sites and leaving different litter acting as traps for birds (e.g. fishing nets, lines, hooks, etc.).
8. Insufficient scientific data
If the real risk of local extinction of the endangered species should be estimated and the conservation priorities should be set, reliable scientific data are necessary. However, intensive monitoring has been carried out only for several selected species (groups) and on selected sections of the project site, and long-term data are even much more rare. Also other type of data (e.g. hydrological) that is needed for optimal site protection is not sufficient.
9. Lack of awareness of authorities, decision-makers and public
Representatives of state administration bodies do not have sufficient information about the possibilities for alternative management of floodplain habitats which would favour the preservation of their biodiversity. And even if they do have some information, they lack the practical experience and relevant know-how. Because the lack of information materials and insufficient media coverage about floodplain (forests) ecosystems, the decision-makers nor the general public are not aware enough about their values and importance. Lack of awareness in state administration bodies results in unsustainable or not appropriate management with a major impact on habitats and species within the whole project site. Lack of awareness of decision-makers and public does not have direct impact on the habitats or species. But without awareness they do not understand the importance of floodplain forest and their biodiversity and the need for their conservation, and they do not support the necessary administrative and conservation measures, which should be taken (e.g. realization of various conservation projects, introducing of better management procedures, enlargement or designation of protected sites).
