Climate observations, derived from the E-OBS dataset, (i.e. the gridded version of the ECA dataset on climate variable) revealed that a general trend in increasing temperature has been observed in Europe between 1960 and 2018, not only in the Mediterranean area but also in central and north-eastern Europe. In the same period, Hungary experienced a significant warming (+ 0.3-0.35 °C per decade), and a major frequency in heatwaves (+6-8 days per decade) (see the EEA indicators on temperature). Precipitation is highly variable during seasons and years, with heavy precipitation events occurring especially in winter. Future projections indicate that these extreme events will increase in the next decades (up to 35%). Drought frequency has increased since 1950, up to +1.3 events per decade (see the EEA indicators on meteorological and hydrological droughts). Climate projections, based on EURO-CORDEX data, indicate an increase in average annual temperature between 2-4 °C, by the end of the 21st century, according to RCP4.5 and RCP8.5 scenarios, respectively (see the EEA indicators on temperature), and a slight increase in drought frequency in the period 2041-2070 in the two emission scenarios (see the EEA indicators on meteorological and hydrological droughts).
These changes are expected to have diverse impacts on the habitats and biodiversity of the Körös-Maros National Park, the extent and timing of which will depend on individual sensitivities to climatic changes, as described below.
Pannonic salt steppes and salt marshes
These habitats are very dependent on the duration of wetting and temperatures, both of which affect salt accumulation and other soil characteristics. Periods of low or no rainfall result in drying of the steppes and marshes (note that there is already a regular trend of drying), while excess summer rainfall may increase leaching of the soil, leading to reducing salt characteristics and thereby salt steppes and marshes degradation. Sodic habitats are among the most endangered as they provide special, complex soil conditions that can support both steppic meadow species (due to humus content), meadow species (due to groundwater effects) and sodic species (due to sodium-salt accumulation at around 1 m depth). If any of these processes/conditions change (becomes stronger or weaker), the habitat composition will change. Variable circumstances and climate extremes, including those as a result of projected climate change, can be beneficial for habitats such as dense and tall Puccinellia swards or Annual salt pioneer swards of steppes and lakes.
Natural eutrophic lakes with Magnopotamion or Hydrocharition - type vegetation
As a projected impact of climate change, decreasing rainfall harms hydrophyte vegetation since the reduced level of water can affect species development and survival, thus simplifying species composition and reducing biodiversity. Species number may fall as species with tight ecological tolerance disappear. Species requiring high naturalness state of habitat (Myriophyllum verticillatum, Ceratophyllum demersum, C. submersum, Utricularia australis, Salvinia natans) will be at risk of disappearing. The increase of less sensitive species is expected.
Pannonic loess steppic grasslands
As species composition of these habitats is dependent on annual rainfall, this may be affected with projected changes in climate. Decreasing water from wet areas during summer threatens species composition as a result of lowering groundwater table.
Alluvial meadows of river valleys of the Cnidion dubii
As a consequence of lowering groundwater table, these meadows are at risk of drying out and, in parallel, becoming weedier. Several of their stands rely on a shorter spring inundation.
Alluvial forests with Alnus glutinosa and Fraxinus excelsior
These habitats are extremely endangered as the water scarcity, due to projected climate change, might impede the renewal /regeneration of tree and shrub species.