Assessing the sustainability of harvest of Pterocarpus angolensis in Rukwa Region, Tanzania
The species is overexploited for its timber which has caused many local populations to become diminished. This exploitation endangers those large trees that are of harvestable size (Takawira-Nyenya 2005). The current harvest of the timber is unsustainable one study showed that if current rate of timber extraction (5.6% per annum) continued in Northern Province, South Africa, all exploitable timber would be gone within the next 30 years (Desmet et al. 1996). Big trees are now rarely seen and there are not thought to be enough small trees to replace these, immature trees are even being harvested to bridge the gap in some (but not all) places (Geldenhuys 2013). The reduction in large trees reduce the amount of seed being produced (Shackleton 2002) but the impact this has on the potential viability of the tree in the future is not currently known.
The species is intrinsically threatened by its poor germination (Boaler 1966) and low seedling survival rate (Takawira-Nyenya 2005). Seedlings will often be browsed by animals putting them at risk and both trees and seedlings are damaged by elephants within the region. The species is also threatened by a fungus (Fusarium oxysporum) that causes dieback known as Mukwa blight or mukwa dieback (van Wyk et al. 1993).
Trees are hand cut, rolled to saw pits, sawn into logs and then removed by truck to a train depot;
In Tanzania, P. angolenesis wood is widely utilized for furniture, veneer, carving and general purpose timber; In South Africa, the sap is used traditionally for treatment of ringworms and ulcers, eye treatment against cataracts, malaria, blackwater fever and skin inflammation, and urinary schistosomiasis;
in Msaginia Forest Reserve (MFR), Settlements and cattle grazing are forbidden in the Forest Reserve but selective harvest of P. angolensis is carried out under license. In practice, most tree cutters spend months in the Forest Reserve and illegally hunt mammals there.
within Katavi National Park (KNP) No temporary or permanent settlements are allowed aside from Park headquarters and two outlying ranger posts; no livestock, beekeeping, hunting, fishing or timber extractions are tolerated. Tanzania National Park rangers conducting vehicle and foot patrols enforce these laws.
The study site was in and immediately south of Katavi National Park (KNP), latitude 68450 –78050 S, longitude 308450 –318250 E at the north end of Rukwa Valley in Rukwa Region, western Tanzania. The second area is Msaginia Forest Reserve (MFR), adjacent and north east of the Park;
Results showed that adult P. angolensis are being removed very rapidly given its slow growth rate as determined from tree ring data, and that regeneration both inside and outside the protected area is very low. A simple model indicates that current harvest is unsustainable raising serious concerns about the long-term viability of this important hardwood species in miombo woodland
In the MFR, We cannot predict when economic extinction will occur within this system, but we can say that the population is heading toward economic extinction rapidly. Discussions with loggers suggest that they believe that there is approximately 5 years to go before they will be forced to leave the area;
Schwartz, M., Caro, T., & Banda-Sakala, T. (2002). Assessing the sustainability of harvest of Pterocarpus angolensis in Rukwa Region, Tanzania. Forest Ecology And Management, 170(1-3), 259-269. doi: 10.1016/s0378-1127(01)00774-5
Results showed that adult P. angolensis are being removed very rapidly given its slow growth rate as determined from tree ring data, and that regeneration both inside and outside the protected area is very low. A simple model indicates that current harvest is unsustainable raising serious concerns about the long-term viability of this important hardwood species in miombo woodland