Homogenisation of Biocultural Diversity: Plant Ethnomedicine and Its Diachronic Change in Setomaa and Võromaa, Estonia, in the Last Century.

When studying the evolution of the use of medicinal plants, it is important to identify what role, and to what extent, external factors and local biocultural diversities play in shaping cultural changes. We chose as a case study, which forms part of a larger project, a religiously and linguistically distinct group, the Seto, and compared their current and past plant use with that of the surrounding Võro. Ethnobotanical fieldwork was conducted in the summers of 2018 and 2019. Current uses of plants constituted 34% of the total registered use reports and 41% of those were used to treat general diseases or used as prophylactics. In total, the medicinal use of 86 taxa was recorded, and of these 48 were prevalent. Strong erosion (the abandonment of 43, mainly wild taxa used historically) and valorisation of the uses shared with neighboring as well as distant regions once part of the Soviet Union, were evident, signalling the potential influence of the centralised distribution of knowledge. The results clearly show that the plant medicine-related biocultural diversities of the two groups have been considerably homogenised, eroded and influenced by the knowledge spread through various means during the Soviet era and over the last 30 years.