A national resource assessment of Cyclopia intermedia (honeybush, Bergtee): threats to wild stocks assessed

Wild-harvested Cyclopia intermedia (Bergtee) provides the bulk of the annual supply for the production of honeybush tea in South Africa. While over-harvesting and illegal harvesting of wild populations are flagged as potentially problematic to C. intermedia wild stocks, no formal quantitative assessment of other obvious threats has been previously conducted. Our study addresses this knowledge gap, considering land transformation, climate change, changes in fire frequency, invasion by alien plant species (IAPs), and other local-scale stressors of anthropogenic and natural origin. Desk top analysis using GIS was carried out to quantify threats on a spatial and temporal scale (≈ 20 years) across the distribution range of the species, supported by field surveys of C. intermedia populations at 102 sites. Our findings showed that land transformation is currently not a threat, and the fire return interval of 18.9 years is within acceptable limits for the fynbos. We consider the single largest threat to wild C. intermedia to be IAP invasions, which occupy 4.2% of the area of natural vegetation in the distribution range, with IAPs present at 57% of sites assessed. Based on SSP1-2.6 (low emissions, sustainable development, climate change scenario), we estimate a 3.4% loss of the projected range of C. intermedia by 2040, reaching 7% under SSP5-8.5 (high emissions, worst-case climate change scenario) by 2070. Harvesting was not considered a threat under current conditions; harvested and unharvested plants were vigorous, plant mortality was negligible, and only 66% of sites showed evidence of any harvesting.