Biological invasions are a population-level phenomenon, not species-level. This study highlights the importance of analyzing non-native species at the population level to understand invasion dynamics, spread, and impact. Using a database of European freshwater macroinvertebrate time series, the research reveals significant variability in spreading speed and abundance trends among populations, indicating that invasiveness and impact differ markedly across species and regions. Species-level risk assessments often fail to capture the complexities of population-level dynamics, leading to discrepancies between assessments and real data. The study emphasizes the need for a shift in invasive species management frameworks to account for population-specific factors, such as local adaptation, environmental context, and population-level traits. Invasive species management should focus on population-level dynamics rather than species-level assessments, considering the diverse ecological contexts and varying degrees of susceptibility. This approach can improve risk assessments and inform more effective conservation strategies. The study also shows that the spread of non-native species is a population-level phenomenon driven by intra-population variability, with factors like local conditions, genetic diversity, and environmental heterogeneity influencing invasion success. The findings underscore the importance of long-term data and population-level analyses in understanding invasion dynamics and developing targeted management strategies. The study concludes that biological invasions must be viewed as population-level phenomena, with management strategies tailored to specific populations and their environmental contexts.Biological invasions are a population-level phenomenon, not species-level. This study highlights the importance of analyzing non-native species at the population level to understand invasion dynamics, spread, and impact. Using a database of European freshwater macroinvertebrate time series, the research reveals significant variability in spreading speed and abundance trends among populations, indicating that invasiveness and impact differ markedly across species and regions. Species-level risk assessments often fail to capture the complexities of population-level dynamics, leading to discrepancies between assessments and real data. The study emphasizes the need for a shift in invasive species management frameworks to account for population-specific factors, such as local adaptation, environmental context, and population-level traits. Invasive species management should focus on population-level dynamics rather than species-level assessments, considering the diverse ecological contexts and varying degrees of susceptibility. This approach can improve risk assessments and inform more effective conservation strategies. The study also shows that the spread of non-native species is a population-level phenomenon driven by intra-population variability, with factors like local conditions, genetic diversity, and environmental heterogeneity influencing invasion success. The findings underscore the importance of long-term data and population-level analyses in understanding invasion dynamics and developing targeted management strategies. The study concludes that biological invasions must be viewed as population-level phenomena, with management strategies tailored to specific populations and their environmental contexts.