Integrating Spatial Availability into ethnobotanical research: Introducing the Spatial Availability Score (SAS)

Abstract

Background: Ethnobotanical research has traditionally emphasized the documentation of cultural importance and patterns of plant use through indices such as the Relative Frequency of Citation and Use Value. While these metrics effectively capture cultural relevance within specific knowledge systems, they overlook an important dimension: the spatial availability of plant species beyond their original ethnobotanical context. Consequently, species with comparable ethnobotanical importance may differ substantially in their feasibility for future application in food systems, medicinal use, or local resource planning due to contrasting geographic distributions.

Methods: Here, we introduce the Spatial Availability Score (SAS), a quantitative index designed to integrate geographic availability into ethnobotanical assessment. SAS is calculated using species occurrence data to estimate the extent of occurrence after spatial outliers are identified and removed through a reproducible statistical procedure based on multivariate distance (Mahalanobis distance).

Results: The resulting measure is normalized within a defined geographic reference area, enabling comparison among species at spatial scales relevant to intended applications, from local to regional contexts. SAS is conceptually independent from existing ethnobotanical indices and is not intended to replace measures of cultural importance or use intensity. Rather, it provides complementary information on the spatial feasibility of ethnobotanical knowledge, allowing researchers and decision-makers to distinguish between culturally important species with restricted distributions and those that are geographically widespread. By explicitly incorporating biogeographic information into ethnobotanical analysis, SAS enhances the interpretability, transferability, and future-oriented relevance of ethnobotanical studies.

Keywords: Ethnobotany; spatial availability; species distribution; extent of occurrence; future food systems; biogeography