Borsodi-Mezöség is the largest alkaline marshland complex on the right bank of the River Tisza. The main wetland types, still preserved in good, natural conditions, are permanent and intermittent marshes, hayfields and wet meadows which form a mosaic vegetation pattern with arid vegetation habitats (such as steppe grasslands on loess and sandy soil). The Site provides important staging habitats and water bodies for migratory birds including the common crane (Grus grus), while a large number of threatened waterbirds nest there. Endangered mammals such as the Eurasian beaver (Castor fiber) and the otter (Lutra lutra) can be found. The undisturbed grasslands constitute the only known current habitat of the southern birch mouse (Sicista subtilis) in Hungary. Traditionally, extensive animal husbandry has been practiced, and other activities include hay and reed harvesting and fishing. The ecological character of the Site is threatened by the regulation of the River Tisza and the spread of invasive species such as desert false indigo (Amorpha fruticosa) and boxelder (Acer negundo). Conservation projects have been carried out under the EU’s LIFE programme.