abstract: In Europe, fenlands now occupy only small areas and are completely protected. In Poland, fenland ecosystems include relatively vast and highly natural regions stretching away into the eastern part of Poland such as in Lublin, the river-basins of the Rivers Biebrza and Narew and in the highest compact forest complex of the country - the Janów Forests /Lasy Janowskie/. The most valuable parts enjoy the utmost protection since they are included in the three National Parks and Natural Reserves: the Polesie Park, the Biebrzański Park and the Narwiański Park plus the Imielty Ług Nature Reserve located in the Janów Forest /Lasy Janowskie/ Landscape Park [12,18,20,21,24,25]. Water and peat ecosystems play an important role in the shaping of the ecological landscape of the country. The considerably autharcic and homeostatic properties of these ecosystems contribute to the stabilization of the whole physio-cenoses, enriching these physio-cenoses in water; they also lead to the formation of ponds and flood waters, increase the surface areas of the lakes and swamps, forming and enriching as they go, the variegate character of habitats, biocenses and ecosystems [20]. In the Lublin Polesie, functional systems of a uniquely natural value were generated in the process of evolution (over a shorter or longer period of time). Rich plant and animal complexes with high species� differentiations were generated in these systems. Many remaining endemic and rare examples of flora and fauna typical of such bog ecosystems are to be found in the area. [19]. In the lakes� ecosystems, species indicative of trophy (oligo-, mezo-, eu- or dystrophy) play a special role. They facilitate the determining of the ecological identity of a lake. The degree of trophic lake differentiation points to the higher or lower diversity of water physiocenoses of this region [5]. Some of the trophic types (limnologic) of the lakes play a very special role in the physio-cenoses discussed. Dystrophic lakes, still numerous in Poland, with specific biocenoses (both phyto- and zoocenoses) with many remaining rare and indicative species belong to this last category [17,19]. On the other hand, for the lakes in their neighbourhood, peat ecosystems are a source of active humic acids which �neutralize� the excessive amounts of nutrients dissolved in them (mineral salts) and contribute to the preservation of their stable trophic status[25]. In the British Isles, some types of peat ecosystems (e.g. low peatlands) are protected mainly because they maintain water at a stable level and �accumulate� nutrient reserves [20]. Fens play a special role in nature protection because they decide water retention, the climate of the region, even that of the whole country, and also the limnologic differentiation of the lakes. They form and maintain the mosaic character of the habitats, their biological diversity and also the ecological stability and resistance of the whole physio-cenoses; hence they should be placed under special protection measures [6,14]. Existing and potential threats to fenland ecosystems For 40 years now, extremely valuable natural fenland ecosystems, rare both in our country and in Europe and located in the unique landscape of the Polesie, have been endangered [6,15,20]. They have undergone more and more intense modification under the influence of big hydrological changes of the terrain caused by deformations in the earth�s surface due to coal mining from the deposits located in the vicinity of the protected areas and the functions of the water system of the Wieprz-Krzna canal. The coal mining technology used, i.e. so-called �dumping�, causes settlement and the formation of shafts which fill with ground and surface water. This latter process leads to the successive formation of so-called hollow reservoirs that can influence both the structure and the function of the natural fenland ecosystems. On the other hand, the water system of the Wieprz-Krzna canal poses the very real danger that the surface water will drain away and outside waters will find their way into these specific natural systems creating unforeseeable biocenotic changes. [13,17-19]. The above phenomena have already resulted in considerable differences in the way the Polesie Nature Park works such as: �the drastic increase in the outflow rate and the lowering of the water level which has led to the exclusion from use of some 60-80% of waterlogged areas due to stagnant surface water [4,9]. � a considerable decrease in natural (inter-peat) water retention and the activation of peat mucking processes throughout vast areas, at the same time as the rapid increase of the eutrophication of the fens, together with the mucking process and agricultural utilization. [1,3,10]. �Destruction of local hydro-chemical, hydrological, and hydro-biological diversification, especially of lake ecosystems by cutting through natural - and usually independently existing - ecological systems with a dense network of ditches [2,4,8,11]. �Introduction of foreign water (from the water system of the Wieprz-Krzna canal) strongly eutrophied and often polluted with harmful chemical substances into the complex ecological system formed over aeons of evolution [7,11]. �A considerable decrease in the ability of the water to naturally self-purify (especially in the rivers) by the increase in its outflow rate, the decrease of natural water retention and the destruction of the natural water-land ecotons which constitute a biologically protective water barrier for fenland complexes against pollution and the excessive inflow of biogens [16,22]. �Deformation of the earth�s surface consisting in the formation of hollow reservoirs resulting from coal mining [24]. Objective and scope of the present studies Despite the vast scale of transformations in the hydro- and pedo-sphere, the high rate of the biological activity of phytocenotic systems, especially in fenland areas, has still been preserved [5, 23]. The above characteristic creates a realistic chance for rescuing or even enriching ecosystems which are already seriously endangered today. However, it would require many complex and long-term studies on the ecological processes taking place in the endangered ecosystems and the activities leading to the re-naturalization of the often large tracts of fenland ecosystems in the functional area of the Polesie Nature Park which gradually, and sometimes rapidly, degrade. The studies undertaken hope to gain knowledge on some of the phenomena taking place in the degraded and threatened ecosystems in the functional area of this Park. The following issues remain to be resolved: �the influence of the increasingly dangerous anthropogenic threats (development, recreation, coal mining) on the functioning and natural status of the physio-cenoses of the Park and adjacent regions needs to be addressed; mining deformation of the earth�s surface and its influence on the formation of water relations and the functioning of lake and fenland ecosystems located in the functional area of the Polesie Natural Park needs to be examined; �the processes taking place in the geochemical and biotic structure of the fenland ecosystems under the influence of the anthropogenic transformations of the natural environment need to be identified. �protection and regeneration regulations for degraded and endangered fenland ecosystems need to be prepared.