Unique Biodiversity Values and Conservation Potential of the Szentendre–Pomáz Plain, a Semi-Natural Lowland Landscape in the Budapest Metropolitan Area (Hungary)

The Szentendre–Pomáz Plain is a former floodplain of the Danube River in the northern metropolitan agglomeration of Budapest, Hungary. Since 1990, the population of surrounding settlements has increased by approximately 50%, resulting in extensive urban expansion, increasing pressure on natural habitats, and the decline of traditional land-use practices. These processes have contributed to ongoing biodiversity loss in the region.

At the same time, climate adaptation increasingly emphasizes water retention at the landscape scale. Such measures require large, contiguous, undeveloped areas, which are becoming scarce around Budapest. The Szentendre–Pomáz Plain still has the potential to provide these ecosystem services; however, authorized and illegal construction increasingly threaten habitat connectivity and local water-retention capacity. To support the designation of the area as a protected site, species occurrences are mapped by taxonomic experts through meandering surveys conducted 2–4 times per year since spring 2024, covering the different habitat types of the study area. Nocturnally active moths are surveyed using light trapping at selected elevated points, while birds are surveyed following the Common Bird Census method.

Despite decades of anthropogenic pressure, the area still supports a diverse mosaic of habitats, including reedbeds, marshes, saline and mesic hay meadows, dry steppe grasslands, shrublands, and softwood woodland strips. Field surveys have recorded numerous protected and Natura 2000 species, including Isophya costata (120 occurrences), Libelloides macaronius, Proserpinus proserpina, Eriogaster lanestris (85 larval nests), Lucanus cervus, Emys orbicularis, Bombina bombina, Caprimulgus europaeus, Circus aeruginosus, Castor fiber, Campanula macrostachya (38 occurrences), Iris spuria, Galatella sedifolia (several thousand flowering shoots), Clematis integrifolia, and Stipa tirsa.

Based on our experience with the management of similar habitats, current management practices, including grazing (mainly by horses) and mowing, are compatible with long-term biodiversity conservation. Minor adjustments, such as delayed mowing on selected parcels and retaining larger refuge strips, could further enhance conservation outcomes. These findings highlight the outstanding biodiversity value of the Szentendre–Pomáz Plain and support its formal protection as a nature conservation area.