The Application of Geospatial Analysis Methods for the Reconstruction of Lithuanian–Slavic Ethnolinguistic Boundaries in Southeastern Lithuania

(1) Background: The article addresses the issue of geospatial dynamics of Lithuanian–Slavic ethnolinguistic boundaries in Southeastern Lithuania (SEL) that were influenced by long-term Lithuanian–Slavic linguistic competition. The aim of the study was to reconstruct the Lithuanian–Slavic ethnolinguistic boundaries and reveal the intensive contact zones in the late 19th century based on published data. Additionally, the study aimed to assess the geospatial changes in the ethnolinguistic situation in the research area during the period 1890–2021. (2) Methods: The ESRI ArcGIS technology geoprocessing tools were applied for boundary reconstruction and geospatial change detection. Cartographic materials, statistical data, and national census information were utilized in the process. (3) Results: The gained results provided a better understanding of Lithuanian–Slavic ethnolinguistic dynamics over space and time in the research area. The study reveals that the ethnolinguistic boundary in the Vilnius–Trakai urbanized area shifted in favor of the Lithuanian language, suggesting its potential influence on the metropolitan suburbs in the future. However, insufficient social infrastructure and weak economic development in rural settlements have led to a negative migration balance, a low birth rate, and rapid population aging. These challenges might have a negative effect on the future survival of the Lithuanian language in the multilingual rural area of SEL, especially considering the recent geopolitical realia in the region. (4) Conclusions: The study anticipates an increase in the influence of the Lithuanian language in the Vilnius–Trakai metropolitan area at the expense of further decline in the rural Lithuanian-speaking population in the next decade.