Upper Kiskunság Lakes
Area: 3905 ha
Biogeographic region: Lower Danube region
Before the regulation of the Danube, floods supplied the area with large amounts of water through meandering creeks and side branches. When the flood receded, most of the water withdrew into a maze of creeks, but flat areas beyond the natural embankments of the water courses remained water-logged. These depressions had no effluent and have given rise to today’s soda lakes and the surrounding diverse wetlands. At the time of the First Military Survey (1783-1784), present day soda lakes were vast marshlands with abundant supplies of fresh water and alluvial deposit from flooded creeks. The salt content of the water of the marshes was probably saltier in dry years due to evaporation and the effect of ground water; therefore salt concentration in the lakes may have been rather fluctuating. Dyke constructions started on both sides of the Danube in the 1840s, detaching the former floodplain, including the Upper Kiskunság Lakes. As a result, precipitation and groundwater remained the only water supply of the depressions and the floods did not flush the area any longer. The former vast marshland got fragmented and the lowest-lying parts became white or black soda lakes. We have records of several hundreds of soda lakes along the low-lying zone of the floodplain, however, by now, most of them have dried out or have open water only in early spring. The biggest ones, namely Kis-rét, Zab-szék, Büdös-szék, Kelemen-szék and Fehér-szék are the most valuable soda lakes of the National Park and Hungary as well.
The highest points of the ridges next to the lakes have loess soils and are covered by loess steppes, while sandy humps are covered by fragments of sandy meadow-steppes, a special representative of lowland steppes. These areas provide habitat for the early spring Green-winged Orchid, Bug Orchid and Dwarf Iris, all of which are legally protected. Descending edges of the ridges are mostly covered by Sagebrush steppe, while, at some places, more humus-rich conditions enable the formation of grassy saline steppe vegetation.
Owing to their uniqueness, soda lakes have always been in the spotlight of researchers. As a result, their diverse fauna has been described in great detail. Zooplankton is represented mostly by Copepods and Water Fleas; they feed on unicellular organisms. The main groups of the benthic fauna include Annelids, Nematodes and the larvae of Dipterans and Caddisflies. The densely vegetated littoral zone of the lakes is home to large numbers of Fire-bellied Toads. Puddles are suitable habitats for the Danube Crested Newt.
The large, shallow and food-rich open water of soda lakes resemble sea shore habitats and are suitable feeding grounds for masses of waterbirds. The area is an internationally recognized stop-over site of waterbirds and a nationally important site for breeding species; therefore, it was among the first areas of the country recognized by the Ramsar Convention. Wild geese roost in the lakes in large numbers from autumn till spring. Dabbling ducks visit the area during migration in the tens of thousands; the most common species include Eurasian Teal, Eurasian Wigeon, Pin-tailed Duck, Northern Shoveler and Garganey. All heron and egret species of the country occur in the lakes. When water levels are suitable, large numbers of shorebirds stop at the lakes during fall and spring migration. Typical breeders of the saline habitats include Avocet and Black-winged Stilt; their breeding population can exceed 100 in good years. Other common breeders include Northern Lapwing and Common Redshank. The island in the Kelemen-szék hosts a colony of 100 pairs of Black-headed Gulls. Scattered among them Mediterranean Gulls, Common Terns and, in wet years, Marsh Terns also breed. Among raptors, Marsh Harrier can be mentioned; it breeds in good numbers in the reeds of Kis-rét and Fehér-szék.
Occasionally, Short-toed Snake Eagles and White-tailed Eagles visit the area from distant nesting areas to feed around the lakes. The number of White-tailed Eagles and Imperial Eagles overwintering at the lakes ranges from 2 to 6. Regular wintering species include Merlin and Hen Harrier, while Peregrines can also be spotted during migration, while hunting for shorebirds. The National Park has kept a herd of cattle and water buffalos in the grasslands surrounding the lakes for a couple of years. They have an important role in managing the grasslands, sustaining the swampy saline habitats and preserving biodiversity.