The dissertation studied the invasion of C4 grasses in European grasslands, focusing on Sporobolus cryptandrus in Hungary as a case study. It highlighted how climate change and human activities facilitate the spread of invasive C4 grasses thriving under warmer and drier conditions. The research identified 133 alien C4 grass species in Europe, showing regional differences in species richness, distribution, and invasion status. Southern and Western Europe have the highest number of naturalized and invasive species, while Northern Europe mostly hosts casual species. Through field experiments and statistical analyses, the study reveals that invasive C4 grasses, such as S. cryptandrus, alter plant community composition, reduce biodiversity, and impact soil seed banks, favoring their own dominance. It was revealed that the species forms a persistent seed bank, which enables a competitive advantage over native C3 species under warming conditions. The findings highlighted the urgent need for adaptive management strategies to mitigate invasive grass spread, particularly through early detection, ecological restoration, and land-use adjustments. The study contributes valuable insights into invasion dynamics and conservation strategies for European grasslands facing increasing environmental pressures.