Size-class prevalence of bulbous and perennial herbs sold in the Johannesburg medicinal plant markets between 1995 and 2001

Commercial harvesting of perennial herbs and geophytes for the medicinal plant trade has resulted in significant levels of resource depletion for several of the species concerned. One way to quantify the impacts is to estimate the number of bulbs harvested annually. Using records of bulb diameters sold in the Witwatersrand traditional medicinal plant markets between 1995 and 2001, the diameter size-classes most prevalent in the markets were ascertained. Thereafter, the number of ‘individual equivalents’ was estimated, i.e. the number of individual bulbs harvested annually equivalent in size to the mean diameter of the bulbs known to be traded. The estimates obtained include scenarios for bulbs of different diameters (reflecting the modal frequencies). The results showed there to be a significant decrease in the modal diameter of Eucomis autumnalis bulbs prevalent in the markets between 1995 and 2001 from 8 cm to 4 cm respectively. The diameters of Drimia spp. bulbs, the most popular species in the Witwatersrand markets, were also decreasing, but the differences were not significant by 2001. Scenarios for the number of Drimia spp. bulbs estimated to be sold to the Witwatersrand TM shops in 1995 ranged from 270 618 to 552 022 bulbs per annum. Gatherers are harvesting smaller and smaller bulbs over time and this is not sustainable at current rates, especially if more smaller bulbs are sold. It is thus clear that cultivation is necessary to mitigate the effects of further exploitation.