Repeated cross-sectional study of knowledge and use of wild food plants in the Caatinga of Northeastern Brazil

Abstract

Wild Food Plants (WFPs) are important for food and cultural security. Despite a global trend of erosion in WFP knowledge, little is known about how people perceive their relationship with these species. This study analyzes how WFP knowledge has changed over time, and how ecological and sociocultural perceptions are associated with current and past consumption, and whether patterns of use abandonment exhibit phylogenetic structure. This repeated cross-sectional study compares data collected in 2008–2010 (T1) and 2024–2025 (T2) in a rural community in the Brazilian Caatinga. T1 data come from a prior ethnobotanical survey in the same community, whose free-listing procedure was replicated at T2 to ensure comparability. In T2, 68 participants completed the free listing; the analysis of citation frequency considered the 40 who cited three or more wild food plants, and 36 completed recall procedures and semi-structured interviews on reasons for use, disuse, and non-use. We also compared citation frequency at T1 with that at T2 augmented by species recovered through recall (T2*). Species were classified as currently consumed, formerly consumed, or known but never consumed. Data were analyzed using Generalized Linear Mixed Models, and phylogenetic signal (Blomberg’s K) in the propensity to abandon use was estimated. Knowledge of WFPs declined between the compared periods when based solely on free lists. When recall records at T2 were included, however, the same comparison showed an increase. Species defined primarily by ecological attributes, specifically environmental availability, were associated almost entirely with past consumption, whereas species defined by sociocultural attributes showed a more balanced distribution between past and current use. We also detected a significant, albeit limited, phylogenetic signal in the propensity to abandon use. The repeated cross-sectional comparison indicates a reduction in spontaneously reported WFP knowledge when methodologically comparable free-list data are considered — though assisted recall showed that part of this repertoire remained accessible. Ecological and sociocultural perceptions were differently associated with consumption status, while evolutionary history accounted for only part of the variation among species.