The status of Faidherbia albida trees in the Hoanib River, Namibia

The Hoanib is an ephemeral river flowing from the highlands of Namibia through the hyper-arid Namib Desert to the Atlantic Ocean. Seasonal floods recharge groundwater that supports riparian woodlands, which are vitally important to wildlife and livestock. Previous studies prior to 2001 found that mega-herbivores are having an impact on the main tree species in the river system, Faidherbia albida. In 2002 two permanent boreholes were drilled for wildlife in order to reduce competition with livestock. This paper presents the results of a survey carried out in October 2012 to assess the current population structure and damage to F. albida in the lower Hoanib River, and to compare it with previous surveys. There was great variability in population structure, growth form, regeneration and elephant damage between the transects surveyed in different sections of the river. Khowarib Schlucht, where there are few elephants, showed a healthy demography, with many juveniles, regeneration, and little damage. Dubis wetland, which is utilised by game and livestock, had no mature trees and one clump of juveniles. Transects between the two boreholes showed low recruitment, little regrowth, and a marked 5m-high browse-line. They were dominated by mature, single-trunked trees with old elephant damage, and healthy canopies. From the “President’s Borehole” downstream there were juvenile trees, fewer mature trees, and thickets. Juvenile trees showed pruning from above and the sides. Near the floodplain, there were only highly pruned juveniles and a few trees in the 20-40 cm DBH size-class. Another visit, in 2014, showed changes to the juveniles at Dubis wetland, but no other changes. Overall lack of Faidherbia recruitment along the mega-herbivore frequented section of the river is of concern for the long-term survival of this important linear oasis. Suggestions are made on key interventions that could be implemented to prevent the loss of these woodlands, which would be a conservation and ecological disaster

Publish DateOctober 7, 2022
Last UpdatedOctober 7, 2022