Vistula as an ecological corridor
According to the Regulations about the Protection of Nature an ecological corridor is “an area enabling the migration of plants, animals and mushrooms”.
Various structures in the landscape can perform the function of an ecological corridor. They are most often belts with natural or semi-natural vegetation among the environment greatly reshaped by humans. Therefore, ecological corridors are also river valleys due to their specific elongated shape and characteristics with vegetation spread in belts along the banks. The presence of aquatic food resources ensures migrating organisms favourable conditions. For that reason river valleys are the most universal form of ecological corridor. Its function as a link between different types of environments is full of “untils” – until they are built or transformed by man. Towns and rural agglomerations as well as industrial facilities located within the valley constitute particularly strong barriers. Also, intensive utilisation of agriculture, as well as garden and orchid use, disturbs the natural plant and landscape balance.
The ideal ecological corridor associated with the river valley, that is appropriate for many species with different needs, should include the river bed (watercourse with accompanying vegetation), a flooding area, both slopes of the valley and a forested area on the plateau at least on one side of the watercourse. This model can be relevant both to smaller watercourses and well as to large river valleys. However, in reality such as situation is very rare, because of the transformation of the environment by humans and their occupation of areas within the river valleys and those adjacent to them.
The valley of such a big river as the Vistula is an ecological corridor playing an important role not only on a national, but also the European scale. This is confirmed by the fact that in the ECONET-PL network project nearly all of it is covered by designated nodal areas as well as sections of ecological corridors with international status. The Vistula Valley is also to a greater extent incorporated in the network of ecological corridors in “The Project of ecological corridors linking Natura 2000 sites”, by Prof. Jędrzejewski and the team.
The mid-embankment area of the Vistula is a significant section on the route of spring and autumnal migrations of a number of bird species (incl. ducks, swans, cormorants, osprey, gulls, terns and waders). It is also an important wintering for many national and northern European species (e.g. ducks, gulls, sea eagles). Sections of the river with a natural character, with islands and sandy sandbanks in the riverbed are of particular importance to some bird species.
Plant seeds, as well as small organisms that are found in the river current are transferred by the Vistula valley. The valley also constitutes an important migration route for fish, despite the constraints of huge migrations through the dam in Wocławek. Also for mammals the Vistula valley is an important ecological corridor and even though some of them bypass the Warsaw agglomeration, nonetheless they pass through the Vistula valley using the narrow strip of natural vegetation on its Praga bank.
Around Warsaw (between Siekierki and Żerański Canal) the Vistula is fully regulated. The left bank is fully developed and has the appearance of a boulevard, while on the right bank the riverbank is regulated by means of the so-called spurs. A small remnant of a flood plain terrace between the anti-flood embankment and the riverbank is overgrown with wicker shrubs and trees (riparian willow and poplar patches). It is an extremely valuable natural area, as it is possible to maintain continuity of the ecological corridor of the Vistula valley within the Warsaw agglomeration.
The left bank of the Vistula is a complete barrier to the movement and migration of all land species. In this situation it is very important to maintain permeability of the corridor through the continuity of natural habitats along the Praga side. Its loss may result in breaking away the connections between the southern and northern populations of many species and will completely make it impossible for land organisms to overcome the barrier, such as a huge city is for them. It ought to be remembered, that birds can overcome certain barriers by flying over them, however, for animals moving on land even small surface barriers, such as fencing, a road or a building, may be an important barrier to migration.
Riparian willow and poplar habitats and riverside willows constitute quite a coherent stream of vegetation in the entire river valley, and what is particularly important, it combines with similar analogous systems in the valleys of Narew and Bug, as well as to a smaller extent in Pilica and San. The breaks occurring in the continuity of these habitats in many cases is the result of human activity. It is also worth noting, that the area of the Vistula’s riparian forests found in the very city centre is an exceptional and unique part of the city’s landscape on a European scale.
Currently, the duty to protect ecological corridors stems from the Habitats Directive, referring to the need to preserve the coherence of the Natura 2000 network. Provisions are binding in Poland since the signing of the Treaty of Accession in 2004. After transposition of the Habitats Directive into Polish law the duty to protect corridors also follows directly from the Nature Conservation Act. Article 33, para. 1 provides that “No persons shall ( … ) take actions that may (…) have significant adverse effect on the conservation objectives of Natura 2000 sites , including in particular (…) to impair the integrity of Natura 2000 sites or its relationship with other areas”. The need to protect ecological corridors, which are so linked, confirms also the scope of the plan for Natura 2000 sites (Art. 29, para. 8 of the Act on the Protection of Nature), which includes “the determining of protective measures to maintain or restore the proper state of the objects under protection of Natura 2000 ( … )”. In light of Article 29, para. 9 pt. 2 of the same Act, these activities also include “the maintenance of ecological corridors linking Natura 2000 sites”.
The necessity to protect ecological corridors is also laid out in the National Strategy for Conservation and Sustainable Use of Biological Diversity (2003). The emergence of this strategy is one of the effects of ratification by Poland of the Convention on Biological Diversity (Rio de Janeiro). One of the operational activities of the strategy is “the restoration and protection of the network of ecological corridors (forest, river and other) ensuring the exchange of genes among various local populations”.
Currently ecological corridors in Poland are not a separate and legally sanctioned form of protection of nature. In the Nature Conservation Act there is merely a notation that protected landscape areas may be created for their protection. This form however, does not provide adequate protection for these structures. That is why it is particularly important to incorporate them in spatial planning on a local scale, as due to their specificity the discontinuity in one place results in the whole section of the corridor not being able to carry out its function and merely becomes “a dead end street”.
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