Methodology of the habitat classification of anthropogenic urban areas in Budapest (Hungary).

The vast majority of floristical and coenological studies focus on the natural vegetation and its remnants in urban environments; however, there is an increasing interest in the systematic exploration of built environments. This survey of the inhabited areas of Budapest launched in 2018 applied a new and detailed methodology. The territorial units of the survey were street sections, where the presence of vascular plants was recorded in ecologically different habitats separately. We laid down the foundations to establish new habitat categories for the habitat classification and mapping of urban ecosystems using a different approach than the Hungarian habitat classification system (ÁNÉR). The method enables us to study the flora of urban ecosystems in detail. We established 18 urban habitat categories, surveyed more than 27,000 survey units and registered 647 spontaneously growing plant species in Budapest. Our survey evinced the spontaneous occurrence of 193 alien species in Budapest, 81 of them are data deficient, while 10 of them are new introductions in Hungary. 53.9% of the aliens are cultivated frequently in Hungary.