Ethnobotany, Traditional Knowledge, and Diachronic Changes in Non-Timber Forest Products Management: A Case Study of Himatanthus drasticus (Apocynaceae) in the Brazilian Savanna. The analysis of factors and processes that affect the traditional knowledge and the management practices deriving from it are essential for devising conservation strategies for non-timber forest products. The purpose of this study is to assess the traditional knowledge and analyze diachronic changes in management systems for non-timber forest products in a case study of an intensely exploited species from the Brazilian savanna, Himatanthus drasticus, commonly known as "janaguba." Janaguba produces a latex of commercial value, widely used in popular medicine in Brazil. Recent pharmacological evidence of its medicinal properties has increased harvesting pressure on this resource. For this reason, we carried out an ethnobotanical characterization of the management systems used to harvest janaguba latex and of the traditional ecological knowledge associated with such practices. Three management systems were identified in latex harvesting, which may have varying ecological impacts on janaguba populations, depending on the amount of bark removed and the time interval between harvestings. 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