Distribution and conservation status of the Endangered pepperbark tree Warburgia salutaris (Canellaceae) in Swaziland

Abstract

The Endangered Warburgia salutaris (Bertol. f.) Chiov. (Canellaceae), a sought-after medicinal plant in southern Africa, is on the verge of extinction as a result of overexploitation for illegal trade. As part of formulating a conservation strategy for the species in Swaziland we sought to determine its distribution and population status and to revise its national conservation status. Field surveys were conducted in all physiographic regions of Swaziland. Eighteen locations of species presence were found, of which 14 were new records. Three were within protected areas, and seven were in areas worthy of protection. The largest subpopulations occurred in two of the latter areas, Ngudzeni and Sitsatsaweni (351 and 230 individuals, respectively), and one unprotected area, Bulunga (250 individuals). Warburgia salutaris has a severely fragmented distribution and an area of occupancy of 192 km2. Of 700 mature individuals 38% were ring-barked and 7% felled, and some subpopulations had ring-barked juveniles. This indicates a plausible decline in number of mature individuals. Most localities in unprotected areas are eroded and invaded by alien plants, indicating a decline in habitat quality. Our findings indicate that W. salutaris should be categorized as Endangered nationally based on criteria B2ab (iii,v). Although this status implies a lower level of threat than the previous national categorization as Critically Endangered, it does not imply an improved conservation effort in the country, but rather a more accurate assessment based on more data. We have clarified the conservation status of W. salutaris in Swaziland, discovered some previously undocumented subpopulations and identified potential conservation interventions. We recommend that this information be used in setting priorities to ensure conservation of the species.