Assegai Tree

Taxonomy
Scientific Name
Curtisia dentata (Burm.f.) C.A.Sm.
Higher Classification
Dicotyledons
Family
CURTISIACEAE
Common Names
Asgaaiboom (a), Assegaai (e), Assegaaiboom (a), Assegaaihout (a), Assegaaiwood (e), Assegai Tree (a), Injundumlahleni (z), Modula-tshwene (ns), Mufhefhera (v), Musangwe (v), Umaginda (z), Umagunda (z), Umbomvane (z), Umguna (x), Umgxina (x), Umlahleni (z), Umlahlenisefile (z), Umphephelelangeni (z), Unhlebe (x), Unlahleni (x), Uphephelelangeni (z), Usirayi (x)
National Status
Status and Criteria
Near Threatened A2d
Assessment Date
2008/01/15
Assessor(s)
V.L. Williams, D. Raimondo, N.R. Crouch, A.B. Cunningham, C.R. Scott-Shaw, M. Lötter & A.M. Ngwenya
Justification
The species has been exploited over most of its South African range due to timber extraction and bark harvesting for the traditional medicine trade. The decline to the population in the last 120 years is estimated to exceed 20% (generation length estimated to be 40 years). Further declines are anticipated in the future due to the species' popularity in the traditional medicine trade. Recent trends show that bark collectors have shifted their harvesting activities to Mpumalanga due to its scarcity in KwaZulu-Natal.
Distribution
Endemism
Not endemic to South Africa
Provincial distribution
Eastern Cape, Free State, KwaZulu-Natal, Limpopo, Mpumalanga
Range
Cape Peninsula to the Zimbabwe-Mozambique highlands.
Habitat and Ecology
Major system
Terrestrial
Major habitats
Forest
Description
Evergreen forest from coast to 1800 m.
Threats
Curtisia dentata is currently threatened by bark harvesting for the medicinal plant trade and suffered declines in the past due to timber harvesting, especially in the southern Cape. Timber exploitation: The species was a highly prized and popular timber tree in the Cape, especially for wagon spokes and furniture (Palmer and Pitman 1972). The tree was a less preferred timber species in KwaZulu-Natal by Fourcade (1886), probably because it occurred more sporadically throughout the province. Sim (1906) recorded that the number of trees felled in the Knysna region in a 12 years period between 1889 and 1900 was 41 432 trees, i.e. an average annual output of 3 452 trees. In the region between Port Elizabeth and East London between 1885 and 1900, 4 484 trees were harvested or 747 trees per year. Output in the Transkei region was lower and figures were included with 'other species'. One implication is that Curtisia density was greater in the southern Cape and decreased along the coast towards KwaZulu-Natal. By 1906, Sim wrote that: "the tree is seldom to be found of mature size except in the most inaccessible localities, having been selected out from most forests long ago". It was also noted that the tree was often felled before it had attained its full size. King (1939) ranked Curtisia as the fourth most popular species in the Knysna forests. In 1900, the percentage of mature trees >30cm was 18.6%; by 1930, it had declined to 6.8% hence large scale harvesting significantly reduced the abundance of mature trees within the forests. King (1939) also recorded that the average timber volume removed annually from 1931-1939 was 444.8 cubic meters per year. If one assumes the average timber volume per tree was 0.28 cubic meters (from Sim 1906), then more than 1 588 trees were removed annually in that nine year period; this is a substantial drop from the 3 452 trees per annum said to be felled in 1900 and an indication of how the demand for timber reduced the population size and the timber availability. Timber extraction still occurs in the Cape forests to a limited extent. Timber felling is known to have occurred within KwaZulu-Natal from the 1800s, but there are few records of the extent to which this occurred primarily because it wasn't as abundant as other species where. McCracken (1987) estimated that only 14 trees were cut in one forest from 1903 to 1910. Taylor (1963), however, reported that there was only one old stump left with coppice shoots in the Nxamalala Forest outside Pietermaritzburg in 1963. Bark exploitation: The use of bark for traditional medicine has probably always occurred, but the exploitation wasn't really documented until the 1980s. Dally (1985) reported that Curtisia bark had been stripped from trees in the Ngele Forest near Harding. La Cock and Briers (1992) reported on bark harvesting in the Tootabi forest; in a sample of 70 trees of different species, four were Curtisia and all four had been ring-barked and three of these were dead. Geldenhuys (2004) recorded Curtisia dentata trees in forest patches in uMzimkhulu. Of the 50 Curtisia stems, 60% of the stems had been harvested. On average, 43% of the bark on the stems up to the branches had been removed. Cunningham (1988) conducted various field studies to observe and measure the extent of damage to trees. In Nkandla, where Curtisia is scarce, large branches of the tree were felled to strip the bark to the tips. Gatherers were also building ladders to maximise the quantity obtained per tree. In Malowe forest in the Eastern Cape, 57% of the stems had had more than 50% of the bark removed. Curtisia is however slightly sensitive to bark removal than some other tree species. Studies by Geldenhuys (2004), showed that there was about 30% edge growth on experimentally harvested trees. The species also tends to coppice. In terms of the species' popularity in the muthi markets, it is one of the most prevalent bark products in the markets and is widely traded in various South African markets. Cunningham (1988) estimated that 54 traders in the KwaZulu-Natal region sold 197 bags of bark annually. The species was classified as 'vulnerable and declining' in the province. Furthermore, it was always nominated as one of 15 species becoming increasingly scarce by herb-traders and herbalists in the province (Cunningham 1988). Dold and Cocks (2002) list Curtisia as the sixth most frequently sold species in the Eastern Cape markets, and estimated that around 2.3 tonnes are sold annually. Within the Eastern Cape, Curtisia is heavily traded and unsustainably harvested (Dold and Cocks 2002). In Johannesburg, the species is frequently traded in muthi shops and was sold by 25% of traders in the Faraday Street muthi market in 2001 (Williams 2007). The bark was also recorded in the Mpumalanga markets (Botha et al. 2001). Scott-Shaw (1999) reported that Curtisia was becoming rare and extirpated in many areas and had a low abundance. It was also a sought after medicinal plant that had been critically exploited over most of its distribution range. At the Medicinal Plant Red List Workshop (14-15 January 2008, Durban), the following points were raised by participants: a) the species was impacted by timber extraction in the past and is currently threatened by bark harvesting for the traditional medicine trade; b) the tree dies if it is not felled after ring-barking, hence allowing for coppice shoot formation; c) significant declines have been observed in KwaZulu-Natal and declines are probably also occurring in the Eastern Cape due its popularity in the muthi trade; d) not much bark harvesting has been observed in Mpumalanga (<1% of trees), but it is popular when it is found (M. Lötter pers. comm.); e) Neil Crouch has only seen the species twice in KwaZulu-Natal in a Drakensberg forest and in Ngome forest; f) M. Ngwenya has observed it in Ngoye and Nkandla forests; g) it is slow growing, but faster than Ocotea; h) Mistbelt forests were cleared of valuable trees a long time ago and therefore one will not see dead trees there now; trees are not regenerating at old harvesting sites (C.R. Scott-Shaw); i) participants were unsure of its status in Limpopo forests; j) the harvesting observed in Mpumalanga is recent (i.e. in the last 5-6 years), and it suggests that there has been local losses of trees in KwaZulu-Natal, hence harvesters are now targeting trees in Mpumalanga; k) there has probably been a 40% loss of mistbelt habitat (e.g. the Karkloof forest) in the last 120 years; l) the species is probably recovering from past medium-scale timber extraction in the Western Cape; m) seeds are bird dispersed therefore they could recolonize old sites. The species has been exploited over most of its South African range due to timber extraction in the past and bark harvesting for the traditional medicine trade. The decline in the last 120 years is estimated to be at least 20%. Further declines are anticipated in the future due to the species' popularity in the traditional medicine trade. Recent trends show that bark collectors have shifted their harvesting activities to Mpumalanga due to tree scarcities in KwaZulu-Natal.
Population
Population trend
Decreasing
Assessment History
Taxon assessed
Status and Criteria
Citation/Red List version
Curtisia dentata (Burm.f.) C.A.Sm.NT A2dRaimondo et al. (2009)
Curtisia dentata (Burm.f.) C.A.Sm.Lower Risk - Conservation Dependent Scott-Shaw (1999)
Bibliography

Boon, R. 2010. Pooley's Trees of eastern South Africa. Flora and Fauna Publications Trust, Durban.


Botha, J., Witkowski, E.T.F. and Shackleton, C.M. 2001. An inventory of medicinal plants traded on the western boundary of the Kruger National Park, South Africa. Koede 44(2):7-46.


Cunningham, A.B. 1988. An investigation of the herbal medicine trade in Natal/KwaZulu. Investigational Report No. 29. Institute of Natural Resources, Pietermaritzburg.


Dold, A.P. and Cocks, M.L. 2002. The trade in medicinal plants in the Eastern Cape Province, South Africa. South African Journal of Science 98:589-597.


Fourcade, H.G. 1889. Report on the Natal Forests. Natal Blue Book. Government Printer, Pietermaritzburg.


Geldenhuys, C.J. 2004. Bark harvesting for traditional medicine: from illegal resource degradation to participatory management. Scandinavian Journal of Forest Research 19(Supplement 4):103-115.


Goldblatt, P. and Manning, J.C. 2000. Cape Plants: A conspectus of the Cape Flora of South Africa. Strelitzia 9. National Botanical Institute, Cape Town.


Grace, O.M., Prendergast, H.D.V., Jager, A.K. and Van Staden, J. 2003. Bark medicines used in traditional healthcare in KwaZulu-Natal, South Africa: an inventory. South African Journal of Botany 69(3):301-363.


King, N.L. 1939. The Knysna forests and the woodcutter problem. Journal of the South African Forestry Association 3:6-15.


La Cock, G.D. and Briers, J.H. 1992. Bark collecting at Tootabie Nature Reserve, eastern Cape, South Africa. South African Journal of Botany 58(6):505-509.


McCracken, D.P. 1986. The indigenous forests of colonial Natal and Zululand. Natalia 16:19-38.


Palmer, E. and Pitman, N. 1972. Trees of southern Africa covering all known indigenous species in the Republic of South Africa, South-West Africa, Botswana, Lesotho and Swaziland. Volume 2. A.A.Balkema, Cape Town.


Pooley, E. 1998. The complete field guide to trees of Natal, Zululand and Transkei. Natal Flora Publications Trust, Durban.


Raimondo, D., von Staden, L., Foden, W., Victor, J.E., Helme, N.A., Turner, R.C., Kamundi, D.A. and Manyama, P.A. 2009. Red List of South African Plants. Strelitzia 25. South African National Biodiversity Institute, Pretoria.


Scott-Shaw, C.R. 1999. Rare and threatened plants of KwaZulu-Natal and neighbouring regions. KwaZulu-Natal Nature Conservation Service, Pietermaritzburg.


Sim, T.R. 1906. The Forests and Flora of the Colony of the Cape of Good Hope. Government of the Cape of Good Hope, Pietermaritzburg.


Taylor, H.C. 1963. A report on the Nxamalala Forest. Forestry in South Africa 2:29-43.


Williams, V.L. 2007. The design of a risk assessment model to determine the impact of the herbal medicine trade on the Witwatersrand on resources of indigenous plant species. Unpublished PhD Thesis, University of the Witwatersrand, Johannesburg.


Citation
Williams, V.L., Raimondo, D., Crouch, N.R., Cunningham, A.B., Scott-Shaw, C.R., Lötter, M. & Ngwenya, A.M. 2008. Curtisia dentata (Burm.f.) C.A.Sm. National Assessment: Red List of South African Plants version 2017.1. Accessed on 2019/09/22

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Distribution map

© C. Paterson-Jones

© C. Paterson-Jones


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