ENVIRONMENT
Climate
The
Biebrza Wetlands lay in the north east region of Poland, known as the
"Green Lungs" region. With an
exception of the mountains, this area has a reputation for being the
coldest region in Poland. Its climate can be characterized as a combination of continental
and sub-boreal, these overlapping characteristics are due to the wide
marshy areas that condense moisture on a very large scale and the valley`s
unique geological formation. Long winters and a short vegetation growth period characterize the
Biebrza valley. The average
year round temperature is one of the coldest of these type lowlands with
the coldest month coming in February and temperatures dropping as low as
-50C. Winters can
last up to 117 days and with average maximum temperatures below zero. Snow
cover can last up to 140 days in the upper basin with a slightly lower
longevity in the southern basin. During the spring and fall,
a range of 57 to 66 frosty days is average. July is the hottest month in the
Biebrza valley with temperatures topping out at 17,80C. The length of the summer ranges
from 77 to 85 days, with daytime temperatures averaging
150C. Foggy nights and morning are quite common and can be seen up to 70
days a year and usually twice that in peaty areas of the valley. The cool air of the
surrounding uplands flows and touches the warm waters of Biebrza, this is
a quick catalyst for condensation of water steam which givens the
appearance of ground fog. The
uplands surrounding the valley to a greater extent has a higher level of
precipitation than the actual valley floor, 600 mm to 510 mm
respectively. As with every
typical lowland valley, winds are commonly strong and have a west to
southwesterly direction. Due
to the valleys high humidity wind storms and tornadoes are rare to almost
unheard of.
Geology
The Biebrza
National Park covers a large part of the Biebrza valley, a huge depression
more than 100 km long. The valley was formed during the central Polish and
Baltic glaciations 10.000 - 30.000 years ago. Since that time, a peat
layer has developed and in places is up to 10 m thick. This peatland
complex covers about 90 000 ha and is the largest and the least disturbed
of its kind in Central Europe. The Biebrza valley is surrounded from the
east, south and west by morainic plateaux formed during the penultimate
(Central Polish) glaciation. In the north, a morainic plateau, formed
during the last (i.e. Baltic) glaciation borders the valley. At the
Augustów outwash plain, the valley lies adjacent to a zone of deep kettles
and lakes. The valley is naturally divided into three basins: the northern
or upper basin (east of Sztabin), the middle basin (between Sztabin and
Osowiec) and the southern or lower basin (between Osowiec and the Biebrza
mouth).
The Upper Biebrza Basin is 40-km long and 1.5- 3.0 km wide. The
peat deposit is 3 to 6 m thick and is partly underlain by calcareous
gyttia. Characteristic features of the relief of the Upper Biebrza Basin
are the moraine outcrops. The middle basin is a somewhat rectangular shape
40 km long and 20 km wide. It is a vast complex of peatlands (45,000 ha)
with peat up to 3 m deep.Sands underlie the peat deposit with gravel
series at the bottom of the northern part and silts and clays in the
southern part. Extensive sandy tracts in many places transformed by eolic
process to dunes and partly submerged by peat distinguish the middle
basin. The Augustowski, Woznawiejski, Rudzki canals and several smaller
canals (constructed in the first half of the 19th century) have
changed hydrological regimes of this part of the valley, leading to a
permanent drop in the water table and drainage of the peatlands. The Lower
Basin is 30-km long and 12-15 km wide. The peat deposit is more than 2 m
thick and is underlain by thick sandy-gravel beds, locally covered by loam
and silt deposits. Small dunes forming islands several metres high are
submerged in the peat of the surrounding flat flood plain. Numerous oxbows
are situated in a 1-2 km wide muddy zone along the
river.
Waters
The protection zone
of the Biebrza National Park surrounds the highly bio-diversified and most
unique Biebrza River. Its headwaters are located in the small moraine
hills of Sokolskie, just south of the small and quaint village of Nowy
Dwór. The length of the Biebrza River is 164 km, draining its waters into
the larger Narew River at the village of Ru¶. Only 10 km is excluded from
the boundaries of the Biebrza National Park; with a catchment area of over
7000 square kilometers the Biebrza Valley is considered one of the largest
catchment areas in Poland surpassing many man made reservoirs. The Biebrza
and the Nieman catchments are connect by the Augustowski Channel a
hydro-technical achievement of the 19th century. This and many
other drainage works contributed to the lowering of the local ground water
table. The Biebrza Marshes are supplied by two ways its water table and
the tributaries that discharges into the Biebrza. The majority of
Biebrza`s tributaries flowing into its waters come from the right bank,
these include the Lebiedzianka, Netta, Koptkówka, Jegrznia, Dybła, Ełk,
Klimaszewnica and the Wissa streams. The tributaries of the left bank
contributes only 24.5% of the Biebrza`s outflow and these streams include
the Sidra, Brzozówka, Biebła Czarna Struga and the Kosódka. From the
headwaters to the river mouth the average elevation decline is 36%, but
taking into consideration that the surface area of the valley, due to its
flooding, this decline can be reduced to 19%. An average yearly flow of
27,5 m3/s was measured at the southern basin village of Burzyn.
Snow thawing in spring is the primary reason for floodings that time of
the year, these floodings contribute to the valley`s highly
bio-diversified and habitat mosaic landscape.
Vegetation
documented more than 70 natural and semi-natural plant associations
recorded in the Biebrza valley. Some of the most dominating and ecologically valuable of these
associations include sedge, sedge-moss, reed communities, and mineral
islands. The most dominant forest associations include black alder, swampy
birch, and peat coniferous forests. Hydrogenic dependent habitats cover
40% of the valley`s total area, and these representative water ecosystems
are riverbeds and numerous oxbows or old riverbeds. Changes of the environmental
condition cause by the Augustowski Channel construction, together with
land amelioration done in the 60`s induce permanent decreasing of the
ground water table. This
decrease of the ground level gave way to many semi-natural communities the
most common being meadow type associations. Frequent anthropogenic
ecosystems found in the valley are pastures, cultivated grounds and
urbanized areas with plant communities surrounding the Osowiec Fortress
being by far the most important.
Flora
Characteristics that
describes Biebrza's flora are: spruce dominated with large amounts of
boreal species and glacial relicts such as Shrub Birch (Betula humilis),
Narrow Small Reed (Calamagrostis stricta), String Sedge (Carex
chordorrhiza), Crowberry (Empetrum nigrum), Labrador Tea (Ledum palustre),
Cranberry (Vaccinium oxycoccos), Moor King (Pedicularis
sceptrum-carolinum), Common Butterwort (Pinguicula vulgaris), Jacob's
Ladder (Polemonium caeruleum) Downy Willow (Salix lapponum), Marsh
Saxifrage (Saxifraga hirculus), Marsh Felwort (Swetia perennis),Cotton
Deergrass (Trichophorum alpinum), Northen Bilberry (Vaccinium uliginosum).
Of the more than 1000 vascular plants found in the Biebrza Valley, more
than 900 of them exist in the Biebrza National Park. 90 vascular plant
species are under strict protection and another 17 are only partly
protected. 45 of these species are listed under the Red Data List of
Endangered Vascular Plants in Poland!, these include Green Spleenwort (Asplenium viride), Variegated Horsetail (Equisetum variegatum), Great Sundew (Drosera anglica), Marsh Pennywort (Hydrocotyle vulgaris), Common Butterwort (Pinguicula vulgaris), Small Fleabane (Pulicaria vulgaris), Yarrow Broomrape (Orobanche purpurea), Marsh Felwort (Swetia perennis), Fritillary (Fritilaria meleagris), Iris (Iris aphylla) and 20 other orchid species
including the Ladies Slipper (Cypripedium calceolus) with one of the most
numerous populations in Poland!
List of vascular plants of the
Biebrza Valley you can find at: http://www.eko.pb.bialystok.pl/flora/
Fauna
The Biebrza valley supports
a unique group of bird species in Europe. About 270 species have been
observed here so far, including 181 breeding birds. Among 56 species
recorded in Polish Red Data Book of Animals (1992), 17 breed in the Park,
e.g.: Spotted Eagle Aquila clanga, Great Snipe Gallinago media, Black Tern
Chlidonias niger, Aquatic warbler Acrocephalus paludicola. For some
waterfowl species, Biebrza marshes are among the last refuges for the
survival of their population in Central Europe. For many groups of
animals, there are only sporadic data. So far 48 mammal species, 13
amphibian species, 5 species of reptiles, 36 species of fish and Ukrainian
lamprey, over 750 species of moths and butterflies, 500 species of
battles, 11 species of bats, 42 species of caddis-fly, about 450 species
of spiders and 19 of leeches have been recorded.
Mammals of Biebrza National Park
List of birds observed at the Biebrza Valley
Threats
One
of the greatest threats to the Park is artificial drainage, which results
in the invasion of marshes by shrubs and trees. This loss of sedge and
moss communities is accelerated as farmers (landowners) cease mowing for
hay production. Active conservation measures are applied to limited extent
to stop further succession and maintain the valuable intermediate stage.
Since 46% of park property is privately owned, agricultural management
compatible with conservation principles is of primary importance, and a
broad public awareness campaign is in place to encourage measures towards
adopting organic farming techniques.
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