The distribution and status of rooibos (Aspalathus linearis) and its ecotypes in the wild

Abstract

Aspalathus linearis (‘rooibos’) is a polymorphic perennial shrub native to the Fynbos Biome (South Africa), which is commercially cultivated and harvested from the wild to produce rooibos tea, a herbal health drink. Ongoing utilisation of the species necessitates knowledge of the status of the species in the wild to facilitate sustainable management of the resource. We assessed the current occurrence, potential distribution, estimated population size and threats to persistence of wild rooibos and its ecotypes. We confirmed previous accounts of the distribution range of wild rooibos, although it was absent from historically recorded locations south of Malmesbury in the Western Cape Province of South Africa. The predicted distribution range of the species is almost 600 000 ha, with relatively little overlap in the predicted ranges of the respective ecotypes (120 000–250 000 ha each). Based on the predicted distribution ranges in conjunction with field-observed population densities, the total population of wild rooibos is estimated, based on crude extrapolation, to be at least 15 million plants and each ecotype at least 3 million. More than a quarter of the species’ predicted range (20–40% of each ecotype’s range) occurs in proclaimed protected areas. Our evaluation of threats suggests that wild rooibos is not significantly threatened by harvesting, invasive alien plants, overgrazing or inappropriate fire regimes. Potential genetic contamination with cultivated varieties, and further large-scale agricultural transformation are unlikely, while climate change arguably constitutes the largest threat. These findings are promising for securing this wild resource in the future, and valuable for informing conservation status and sustainability assessments, resource management and monitoring.

Significance:

• The study presents a national assessment of the status of a biotrade resource, rooibos (Aspalathus linearis), in the wild.
• The species’ estimated population is at least 15 million plants and its predicted distribution 600 000 ha, of which >25% occurs in proclaimed protected areas.
• Climate change arguably constitutes the largest threat to wild rooibos, more than harvesting, inappropriate fire regimes, genetic contamination and further habitat transformation.
• These findings are promising for securing this wild resource in the future and valuable for informing conservation status (e.g. IUCN Red List) and sustainability (e.g. CITES Non-Detriment Finding) assessments and monitoring.