Euphorbia barnardii A.C.White, R.A.Dyer & B.Sloane
Status and Criteria
Endangered A2ace; B1ab(ii,iii,iv,v)+2ab(ii,iii,iv,v)
|P.J.D. Winter, S.J. Siebert, R.H. Archer, J.E. Victor & L. von Staden|
|EOO 500 km², AOO 0.3-1 km², known from three to five subpopulations and locations and the total population estimated to be fewer than 10 000 mature individuals. Threatened by overgrazing, trampling, habitat degradation, erosion, disease and mining. Monitoring over the last 15 years recorded extensive declines in three subpopulations, with two formerly large subpopulations not being relocated and one showing more than 80% decline in the number of mature individuals. A 60-70% decline in the total population in last 15 years is estimated (generation length 10-20 years).|
|South African endemic|
|Sekhukhuneland, from the Strydpoort Mountains southwards along the Leolo Mountains to Steelpoort.|
Habitat and Ecology
|Sekhukhune Plains Bushveld, Ohrigstad Mountain Bushveld|
|Savanna and closed woodland, rocky slopes and summits, mainly norite outcrops, with one subpopulation on banded ironstone. At most sites the habitat has been degraded to a shrubby, succulent-dominated vegetation with low grass and tree cover.|
|E. barnardii is threatened mainly by overgrazing and trampling by livestock which damages plants, especially the terminal flower bearing stems which also then results in poor reproduction, disease, habitat loss through erosion and expanding human settlements and to a lesser extent mining and harvesting for horticultural purposes.
Grazing and trampling is affecting all known subpopulations of this species. Monitoring and surveying of subpopulations over a five year period, 1989-1994/5 indicated that plant density are much lower on accessible lower slopes close to human settlements than on ridge and hill summits. However, four out of five subpopulations appeared healthy and monitoring indicated a 75% decline in only the most heavily impacted subpopulation. Subpopulations were large, consisting of between 700 and 4000 mature individuals. However, more recent revisits to the sites (2006/2007) indicated a far worse situation, only three of the five subpopulations could be relocated, and the Bewaarkloof subpopulation, which consisted of an estimated 700 mature individuals in 1995 were severely reduced and only about seven plants could be found (P. Matlamela/P. Manyama pers. obs.).
Disease also appears to be a serious threat to this species. In 1995 about 90% of plants at Bewaarkloof were found to be diseased, and disease is thought to be the result of plants being damaged by livestock trampling and baboons (Knowles and Witkowski 2000) or perhaps the more shady conditions at this site (R.H Archer pers. comm.) The combination of trampling and disease appears to have led to radical declines in this subpopulation in the last 10-15 years.
A comparison between historical aerial photographs of the sites indicated that all four sites except Bewaarkloof were impacted by expanding human settlements in a 30 year period between 1957 and 1986. One site was particularly severely impacted and heavy overgrazing resulted in erosion of soils. At this subpopulation extensive declines was recorded during a five year monitoring period.
As this species occurs on mineral-rich norite substrates, it is also potentially threatened by mining. Many of the sites occur near disused mines, but there has recently been a renewed interest in mining in the area which may impact on many norite endemics of the Sekhukhuneland area.
Three out of five subpopulations appeared to be large, healthy and stable in 1995, however, more recent visits indicated that there were severe declines since then as only three subpopulations could be relocated and one showed a > 80 % decline in numbers of individuals. Remaining subpopulations are much reduced from the numbers of 700 - 4000 mature individuals per subpopulation recorded in 1995, and it is therefore estimated that there has been a 50-70% decline in the population in the last 15 years. There were declines in the population between 1957 and 1995, but these declines were probably small and the overall decline in the last three generations is unlikely to exceed 80%.|
Subpopulation sizes estimated by Knowles and Witkowski (2000), data captured in 1995:
1. 710 (estimated using density and area of occupancy measures)
2. 4076 (estimated using density and area of occupancy measures)
3. 2676 (estimated using density and area of occupancy measures)
4. 2444 (estimated using density and area of occupancy measures)
5. 877 (Counted).
|Winter, P.J.D., Siebert, S.J., Archer, R.H., Victor, J.E. & von Staden, L. 2008. Euphorbia barnardii A.C.White, R.A.Dyer & B.Sloane. National Assessment: Red List of South African Plants version 2017.1. Accessed on 2020/01/18|