NATURE

Zielona Dolina Odry i Warty

Islands of life

Wyspy Życia from Sky Art on Vimeo.

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Description of environmental conditions

A FEW WORDS ABOUT THE LOCATION AND GEOGRAPHICAL ENVIRONMENT.

“Błota Warciańskie” is a name derived from the translation of the historical name “Warthebruch” – a small region in Dolina Dolnej Warty, which is a part of Pradolina Toruńsko-Ebserwaldzka, between Gorzów and the river of Warta’s river mouth flowing into the Odra river. The name of the region (Błota = marshes) accurately describes its hydrological specificity.The genesis of Dolina Dolnej Warty’s landscape, as well as the genesis of the whole Pradolina, is related to the influence of a gigantic ice sheet which quartered there over twelve thousand years ago. With the help of the Earth’s climate getting colder and colder, not allowing it to melt, it was continuously moving south from Scandinavia for over five thousand years. The stadials of Baltic glaciation (the last one) left behind lots of terminal moraines (acclivities which came into existence by the subsidence of soil coming from the inside of the ice sheet during its melting) and urstromtals (dips created by the water of the melting ice sheet scouring out soil). One such urstromtals in western Poland, the youngest and the northernmost, ranging from Płock on its eastern border, through the Wisła’s, Brda’s Noteć’s, Warta’s and Odra’s valleys to Eberswalde (in Germany), is the Pradolina Toruńsko-Ebserwaldzka, with Błota Warciańskie being a part of the valley floor.
The remnant testifying to these phenomena is the size of the urstromtal. Due to the scouring effect of the glacial water, an enormous amount of soil was carried away, leaving behind a depression about 50 meters deep and 10 kilometers wide. Hence the valley floor, with Górzyca, Kostrzyn, Słońsk, Witnica, a part of Gorzów and many more eastward villages, is set lower than the usual altitude of this part of the continent.

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The climate of Błota Warciańskie is a temperate one, intermediate between continental and oceanic, with a visible domination of the latter. The growing season lasts about 220 days, the average annual temperature is 7.9oC, the average temperature in January is -1.5oC and 17.7oC in July. The annual precipitation (measured in Kostrzyn nad Odrą) equals to 534mm. The mild climate of this region is not only a result of masses of oceanic air incoming from west through the wide Pradolina Toruńsko-Ebserwaldzka, but also of the presence of big forests, which contribute to an increase in precipitation and air humidity, and a decrease in the temperature amplitudes in comparison to the areas without forests. Ground frosts occur more often on the valley floor than on moraine plateaus due to the cold masses of humid air gathering there, which create climatic contrasts in the cross section of a wide depression.

“MARSHY” TOPICS.
Hydro-engineering of Dolna Warta–centuries of taming the wild region.

The present landscape of the estuarine part of the Warta river is an effect of man fighting with the forces of nature. Its creation and complex functionality is the effect of two hundred years of work aimed at taming this difficult, marshy region.

A schematic map of Dolna Warta, dated 1720, showing the landscape of the region before the undertaking of the great land reclamation.


To the beginnings of the 18th century, the valley floor of Dolina Warty comprised of unhabituated marshy land. The presence of man was restricted to the dry high ground bordering the unfriendly area. The mouth of the Warta river formed a typical delta at this time: it lacked the main stream channel and had a labyrinth of twisting, tiny distributaries; it also had many islets, lakes of various sizes and shallow backwaters.

A swampy forest in Dolina Warty. Back in the past, the valley floor was completely overgrown with a similar forest, creating the so-called “impassable wilderness”.


The changes came in the second half of the 18th century, when the rulers of Prussia decided to start land reclamation, with the purpose of dilating and embanking the Warta river, as well as reclaiming most of the area cleared of woods and forests. Frederick the Great saw a great opportunity for increasing the population of the country in embanking the channels of the Odra and Warta rivers. It was meant to be done by settling newcomers from foreign countries on the reclaimed land, which would result in an increase in the number of people paying taxes.

The conceptual part of the work on the land reclamation of Dolna Warta was done in 1763 by signing a contract with an engineer, Isaac Jacob von Petri, for measuring Błota Warciańskie and laying down the way in which they should be reclaimed. However, before the process of reclamation could be started, Frederick the Great first decided to “acquire” settlers (of German origin), which, for strategic reasons, were the vital part of the whole undertaking. Due to the amount of people, the king had to prepare them a place to live. These events could have had an influence on his decisions, forcing him to settle the newcomers first and set aside the quality of the project.
The range of land reclamation works involved:
– embanking the northern bank of the Warta river in the years 1767 – 1787;
– building a network of drainage ditches in places separated from the influence of the river (even though some ideas predicted using the network for irrigation during droughts);
– digging out a several-kilometers-long channel in 1780s, later named Kanał Fryderyka Wilhelma, which is now the river mouth of the river;
– barring the old river mouth located in the neighborhood of Brama Chyżańska in Twierdza Kostrzyń;
– building a left-bank embankment of the Warta river between Słońsk and Kostrzyń in the years 1828 – 1832;
– building a left-bank embankment to Słońsk and connecting it with the embankment of the Postomia river in 1842;
– building a number of pumping stations dewatering the areas where gravity flow is not always possible.

Embankment built near the town of Witnica at the end of 18th century, functioning as a barrage for the Warta’s floodwater up to this day.


As a result of building embankments, an area of 30 000 hectares has been separated from the influence of the Warta’s floodwater. Even the eighteenth-century engineers already knew that a total elimination of floodplains would bring a risk of the embankments being breached by water, no matter how high they would be. The water has to be contained somewhere, but the narrow channel going between two parallel levees does not have enough volume to keep it in. In the years 1828 – 1832 a storage reservoir, called Kostrzyński Zbiornik Retencyjny, providing a safe place for storing the excessive water, has been built. It has been storing the overflowed water of the Warta and Odra rivers, which had been previously spilling over the rivers’ floodplains. It was created by moving the course of the southern embankment farther away from the Warta’s riverbed. It encircles almost 5 100 hectares of terrain (a fragment of the former delta)between Słońsk and Kostrzyn, creating a wide hemicycle. This area, between the levee and the Warta’s riverbed, functions as an enormous water container. Since the land reclamation works presented above only slightly affected the Kostrzynski Zbiornik Retencyjny, it kept its natural hydrography quite unchanged.

The colonization of Błota Warciańskie.

The colonization and nomenclature of settlements in Błota Warciańskie (dated back to the turn of the 18th and 19th centuries).


The appearing of the first “Olędrowie” was connected with the attempts of reclaiming Żuławy by the people of Gdańsk and the Teutonic Knights, who brought over the masters of such tasks – the Dutchmen. However, the genesis of the bigger Olęder settlement movement was related to the sixteenth-century reformation movements in western Europe and the religious persecutions accompanying them. It lead to an emigration of thousands of Protestants (including a big amount of Mennonites) from Friesland and Northern Netherlands to Germanic countries. They were later also recruited by the agents of Polish liege lords for establishing new settlements in Dolna Wisła’s wetlands and in the valley of the Noteć river, etc. The remnants of the Olęder colonization are visible even today: in the architecture of the countryside, the spatial order of villages, and even in their names (Holendry, Olędry, Olendry).

Studzionka – a village established in 1722 (45 years before the embankment of the Warta river!) by the first 14 Olęder families brought in for the sake of building new settlements. Up to this day, the village has preserved its unique “boggy” character.


The colonization of Błota Warciańskie was conducted simultaneously with the process of land reclamation. In total, after a terrain of 30 000 hectares has been reclaimed from the river, 15 thousand people found there a place to live. They established 10 new villages and 37 colonies. The settlers were mostly of Polish origin. The duties of the inhabitants living in the villages in Błota Warciańskie included maintaining the embankments and other elements of the land-reclaiming devices.

The separation of the Warta’s valley floor from the influence of floodwater made it possible for man to reclaim formerly impassable swampy forests, establish settlements and create meadows and fields.


THE NATURE OF BŁOTA WARCIAŃSKIE – A GRAND FEAST FOR THE SENSES.

The land reclamation works, started in 18th century, introduced many changes to the natural environment. Aside from clearing the area of woods and forests and transforming woodlands into agricultural lands, the aquatic conditions of the area were also altered significantly. These transformations have had an unquestionable influence on the natural value of Błota Warciańskie. As a result of embanking the Warta river, about 30 000 hectares of land has been cut off from the river water’s influence. The once vast floodplains suddenly ceased to exist. They were transformed into agricultural lands with stable hydrographic conditions, guarantying safety to the newly established settlements, the inhabitants and their crops.

The landscape of the reclaimed area of the valley is a very distinctive one. It is mainly composed of vast, plain meadows, interspersed with ditches, channels and sparsely-placed steadings. The remnants of the former delta, including twisting oxbow lakes, boggy alder forests and willow thickets, can be stumbled across here and there. The area depletion of the terrain storing the overflowed water caused a need for a substitute to the problem of excessive H2O. A water container capable of storing all the water previously spilling over a bigger area of land was built. This is how the Kostrzyński Zbiornik Retencyjny came into existence. The water level oscillates greatly during the year and the difference between the lowest and the highest level can be as big as 4 meters. Thus, the lands between embankments and the area of the storage reservoir are characterized by remarkably dynamic hydrographic conditions. The two main factors that play the biggest role in the process of forming habitats are water, which imposed many changes described in this paragraph that had to be carried out by man in order to reclaim the land, and agricultural exploitation of land. The landscape of floodplains, outside of the flooding period, consists of vast meadows interspersed with oxbow lakes, diversified by small bodies of water, clumps of trees and bushes. Such conditions are very friendly to water and wetland birds.


The river system on an area of over 5 000 hectares remain unchanged, thanks to what a natural fragment of the former delta of the Warta river has been saved. Due to that, and the fact that since the 1970s it has been considered as an area of the highest natural value, a nature reserve Słońsk was created there.


Vegetation is mainly represented by reed bed and common club-rush plant community, and herbal and meadow plant community. Of the protected plants one can come across: early marsh-orchid Dactylorhiza incarnate, European white water-lilly Nymphaea alba, yellow water-lilly Nuphar lutea and fen ragwort Jacobaea paludosa. The flood character of the Kostrzyński Zbiornik Retencyjny provides suitable conditions for reproduction, feeding and wintering for many species of fish. An evidence proving how important this area is for the ichthyological fauna might be the fact that the fish from the estuarine section of the Warta river, and even the Odra, come here for spawning.
The composition of species in the estuarine section of the Warta river, the middle reaches of the Odra and the Dolna Postomia is dominated by common bream Abramis brama, ide Leuciscus idus, northern pike Esox lucius, tench Tinca tinca and roach Rutilus rutilus. Aside from using the overflowed water as spawning ground, the fish utilize it for feeding. They also use the deeper section of the Warta and Postomia rivers as their wintering place. Among many other species of fish, a few protected ones can also be seen, including: amur bitterling Rhodeus sericeus, European weatherfish Misgurnis fossilis, stone loach Barbatula barbatula and spine loach Cobitis taenia. The improving quality of the Warta’s water even enabled the Salmonidae to come back to the river’s smaller tributaries, i.e. Atlantic salmon Salmo salar and brown trout Salmo trutta.

Shallow waters are used as spawning ground. Northern pike Esox Lucius is visible in the photo.


Diversified wetland habitats are an exceptionally attractive environment to live in for many members of Amphibian species. Loud frog concerts coming from the spring backwaters evidence a large population of this group of animals. They could even become the symbol of Błota Warciańskie, as they can be easily heard almost everywhere in the region. The most numerous frogs are marsh frog Pelophylax ridibundus and edible frog Pelophylax kl. Esculentus. Among them, a variety of less numerous species can be seen there, i.e. moor frog Rana arvalis, common frog Rana temporaria, European fire-bellied toad Bombina bombina, common spadefoot Pelobates fuscus, natterjack toad Bufo calamita, common toad Bufo bufo and European green toad Bufo viridis. The usually xerophilic reptiles are represented by numerous grass snakes Natrix natrix and less numerous sand lizards Lacerta agilis. The differences in the population of these species in Błota Warciańskie is caused by the vast amounts of aquatic habitats and smaller amounts of places suitable for xerophilic reptiles. The mammals of the region are represented by almost forty species. Aside from the native Eurasian beaver Castor fiber, European otter Lutra lutra, European badger Meles meles, least weasel Mustela nivalis, stoat Mustela erminea, beech marten Martes foina, European pine marten Martes martes, European polecat Mustela putorius, red fox Vulpes Vulpes, roe deer Capreolus capreolus, red deer Cervus elaphus and wild boar Sus scrofa, unfortunately, some invasive species, whose homeland lies thousands of kilometers away, are also present. These include: American mink Neovison vison, raccoon dog Nyctereutes procyonoides and raccoon Procyon lotor. All of them got there with the help of man and, as they are unknown to the local nature, they pose a threat to its fauna and flora.

A beaver by a lodge.


A male roe deer on an islet in wetlands.


The hydrological specificity and exploitation of land made Błota Warciańskie a very important place for migratory, wintering and molting birds. Also the birds that do not migrate and hatch where they live found it suitable for reproduction. Out of all animals in the region it is the birds who are the Błota’s greatest environmental value. The flood character of the valley in the Warta river’s estuarine section and the vast areas of fields and meadows are an attractive, complementary and mutually supportive habitats, which were reclaimed in the majority of European countries.
In the backwaters of the lower reaches of the river Warta the presence of over 250 species of birds has been observed, of which 170 are birds that hatch there. The birds nesting here annually are: waders (common redshank Tringa tetanus ,black-tailed godwit Limosa limosa, common snipe Gallinago gallinago, little ringed plover Charadrius dubius, northern lapwing Vanellus vanellus and Eurasian oystercatcher Haematopus ostralegus), gulls (common gull Larus canus, black-headed gull Chroicocephalus ridibundus, European herring gull Larus argentatus, little gull Hydrocoloeus minutes and Mediterranean gull Ichthyaetus melanocephalus), terns (common tern Sterna hirundo, little tern Sternula albifrons, black tern Chlidonias niger, whiskered tern Chlidonias hybrid and white-winged tern Chlidonias leucopterus), rails (corn crake Crex crex, water rail Rallus aquaticus, little crake Porzana parva, spotted crake Porzana porzana, Eurasian coot Fulica atra and common moorhen Gallinula chloropus), ducks (mallard Anas platyrhynchos, garganey Anas querquedula, Eurasian teal Anas crecca, gadwall Anas strepera, northern shoveler Anas clypeata, common goldeneye Bucephala clangula, tufted duck Aythya fuligula and common pochard Aythya ferina) and grebes (black-necked grebe Podiceps nigricollis, great-crested grebe Podiceps cristatus, red-necked grebe Podiceps grisegena and little grebe Tachybaptus ruficollis).
The early-spring backwaters become an undulant, raucous and multihued palette of vivid colors for a short period of time. During the time of passages, the spring shallow backwaters allure northern pintail Anas acuta, Eurasian wigeon Anas penelope, mallard Anas platyrhynchos, gadwall Anas strepera, garganey Anas querquedula, northern shoveler Anas clypeata, Eurasian teal Anas crecca and common shelduck Tadorna tadorna; while in deep water one can spot contrastively coated common goldeneye Bucephala clangula, tufted duck Aythya fuligula, common pochard Aythya ferina and seaducks: smew Mergellus albellus and goosander Mergus merganser. Sometimes, but not annually, another magnificent animal appears – a beautiful duck with a big, rusty head – red-crested pochard Netta rufina. On open water, the ducks are often accompanied by flocks composed of thousands of geese, mainly bean goose Anser fabalis and greater white-fronted goose Anser albifrons. In a slightly different scenery of flooded meadows yet another phenomenon impressing with its scale takes place – the spring passage of waders. Only then numerous flocks of northern lapwing Vanellus vanellus and European golden plover Pluvialis apricaria can be observed, as well as smaller numbers of beautifully coated spotted redshank Tringa erythropus, common redshank Tringa tetanus, wood sandpiper Tringa glareola and other species. The first days of spring in the bird world are the days of a palpable tension related to the need of finding suitable breeding grounds. The faster the bird, the easier it is for it to find a good breeding ground, the quality of which directly affects the breeding success.

Courting shelducks.


It is worth to mention the courtship displays of ruffs as one of the most spectacular events. The male members of this species, perfectly knowing their roles, are coated in distinctive, colorful plumage. What is more, the coats of males vary so greatly that two identically coated ruffs have never been observed, so the courtship display transforms into a colorful blend, where the actors simulate a fight with great commitment and vibrancy by jumping, running in circles and freezing only to attract a cohabitant. Fortunately, no ruff is hurt in all this commotion. The performance lasts up to a dozen or so days, after which almost all the birds fly farther northeastward to their main breeding grounds.

Courting ruffs.


A male ruff in its full, mating plumage.


Not less interesting is the observation of yet another magnificent animals of this region – the terns. The territory of Błota Warciańskie is the breeding ground for as much as five species: common tern Sterna hirundo, little tern Sternula albifrons, black tern Chlidonias niger, whiskered tern Chlidonias hybrid and white-winged tern Chlidonias leucopterus. All of them are characterized by the grace with which they move in the air. The common and little terns are connected with the open water environment where they hunt. They also need hard gravel substrates for their nests. The way they fly and hunt is a real aerial ballet –having chosen a fish of suitable size they fall onto it, diving into the water impetuously. However, other species of terns, like black tern Chlidonias niger, whiskered tern Chlidonias hybrid and white-winged tern Chlidonias leucopterus hunt and nest slightly differently. The observation of them is a real feast for the senses. Their plumage consists of only two colors contrasting each other – white and black, occurring in variable intensity and hues depending on the species. All of them nest in small colonies on floating platforms built of aquatic plants.

Courtship displays of Little terns.


White-winged tern’s hunt


In spring, Błota Warciańskie is one of the most suitable place for observing grebes. It is a really colorful group of aquatic birds with interesting mating behaviors. For example, red-necked grebe Podiceps grisegena produces distinctive sounds, similar to the oinks of a pig, during its mating ritual. Black-necked grebe Podiceps nigricollisis, on the other hand, is magnificently colorful in its mating coat, it has ruby-red eyes and a sheaf of golden feathers behind them. For black-necked grebe, a rare species in Poland, Błota Warciańskie is one of the most important breeding grounds and it is relatively easy to observe it there. The most numerous in Poland of all grebes, but in minority in this region, great-crested grebe Podiceps cristatus attracts attention with its distinctive mating dance, composed of simultaneous bows and head shakes of both mates. Two crests made of sheaves of feathers, from which the name of the species was coined, are clearly visible during the mating process. Little grebe Tachybaptus ruficollis, the smallest and most brisk of grebes, also comes there for breeding.

Red-necked grebe building a nesting platform.


Black-necked grebe


At the end of the breeding season, the floodplains of the estuarine section of the Warta river are an attractive place for some species of aquatic birds to undergo the process of molting. It is why up to dozen or so thousands of birds, mainly ducks (mallard Anas platyrhynchos, garganey Anas querquedula, Eurasian teal Anas crecca, gadwall Anas strepera and northern shoveler Anas clypeata), greylag geese Anser anser, mute swans Cygnus olor, Eurasian coots Fulica atra, common cranes Grus grus. The essence of this process is an exchange of worn out flight feathers for new, fully operational ones. It is a sort of a preparation for the upcoming challenge – the migration to winter habitats. Depending on the species, the process take anywhere from three to five weeks. During the time of molting, even though there can be numerous birds, it is very hard to see any. It is caused by the need of hiding from dangers, which is greater than usually during the process of exchanging feathers.

The rails lead a very secretive lifestyle. It is very unusual to observe them. The image depicts a spotted crake Porzana porzana.


Water rail Rallus aquaticuswith its offspring.


The autumn migrations of birds are aimed at reaching the winter habitats. Some specimen set off very early, even in July, usually due to losing their clutch or not having hatched at all. Some species occur in the highest density in this time of year. These include mainly waders: wood sandpiper Tringa glareola, Eurasian curlew Numenius arquata, common snipe Gallinago gallinago and spotted redshank Tringa erythropus, whose coats might not have its usual dusky color yet, because of the process of exchanging the coat for its ashen variation, used only outside of the breeding season. Ruff Philomachus pugnax, common redshank Tringa totanus, common greenshank Tringa nebularia and black-tailed godwit Limosa limosa also change their coats for the version used outside of the breeding season in this time of year.

A mustering of storks.


At the end of summer, some species of birds group together before setting off to their winter habitats. It mainly applies to white stork Ciconia ciconia, black stork Ciconia nigra and primarily to common crane Grus grus. At the end of August, storks gather together into groups called musterings. The birds do so in order to undertake a joint journey to their winter habitats. Black storks also gather before departing. Groups ranging from a few to a dozen or so members can be observed most often. Sometimes, the number of birds in a group can exceed one hundred. Undoubtedly, the gatherings of cranes, called sedges, exceed them greatly, as the number of specimen can be as high as five thousand! Groups of cranes can be seen as soon as in July, usually counting up to about several dozen birds. Those are usually young cranes, and those adults which lost their clutch and did not hatch the second time, or did not build a nest at all. In the course of time more cranes arrive, so their clangor quickly dominates both the morning and evening silence. The observation of cranes departing in the morning is particularly recommended, as uncountable silhouettes of birds crossing the pink hues of the morning sky create a magnificent view.

All pictures were captured with the use of Nikon cameras, with technical support of the company’s representative: Nikon Polska sp. z.o.o. during the process of environmental monitoring associated with the realization of the project.
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