Zasavica Wetland Complex is the First Category Special Nature Reserve since 1997 and covers 1,821 hectares, of which 671 hectares are under the second level of protection. The reserve watercourse is 33.1 kilometres long, located in the Northern Mačva region, east of the Drina river and south of the Sava river, in the municipalities of Sremska Mitrovica and Bogatić, under the absolute impact of water from the Drina river.
Zasavica reserve is abundant in rare plant and animal species, some of which are on the verge of survival. More than 600 plant species, 280 fungus species, 65 mammal species, 216 bird species, 27 amphibian and reptile species, 20 fish species and more than 500 species of a variety of invertebrates are recorded. For 90 discovered flora and fauna species, Zasavica is the first finding in Serbia.
Of nearly 700 plant species in Zasavica, the most significant finding within the reserve flora is waterwheel plant (Aldrovanda vesiculosa), discovered in 2005. This plant had been recorded as extinct in Serbia for nearly 100 years, and Zasavica is its only site in Serbia. The waterwheel plant is a relict species dating from the Tertiary, found mostly in the warm waters in the tropics, where it is distributed sporadically. It is listed on the European flora Red Book; in many European countries, the plant is either extinct or endangered – it is critically endangered insectivorous (carnivorous) plant species.
The ferruginous duck (Aythya nyroca) is a globally endangered species (SPEC 1 species), whose numbers decline due to loss of habitat. On the IUCN Red List, it is listed as near threatened species around the world. Its European population is in rapid decline, and the ferruginous duck is listed as vulnerable species in Europe. In the modern period, this bird is a regular breeder in Zasavica whose nesting population is assessed at some 20-25 pairs, making 4.74% of the national population. All the researches made so far have shown that the reserve has large international importance in the preservation of overall flora and fauna.
