Title:

Chapter 5: The influence of elephants on Faidherbia albida trees in the northern Namib Desert: a reappraisal. In: An Ephemeral Perspective of Fluvial Ecosystems: Viewing Ephemeral Rivers in the Context of Current Lotic Ecology

Author(s):
Publication Year:
1997
Abstract:

Elephants (Loxodonta africana) are well known for the tremendous effect they can exert on their habitat. The Namibian media expressed concern in the early 1980's regarding the influence of desert-dwelling elephants on vegetation within the lower Hoanib River in the northern Namib Desert. A subsequent survey reported no detrimental effects, although my observations in 1994 suggested significant tree damage had occurred since. I resurveyed the area in 1995 to quantify the changes that had occurred in the past 12 years, and considered several hypotheses to explain them. I found that a significant change had occurred in the size structure of the Faidherbia albida forest. Of the 638 trees I examined within the lower Hoanib River, 196 (30 %) were dead and exhibited evidence suggesting they had been killed by elephants. Of the 196 dead trees, 142 (73 %) were <20 cm in diameter. As a result of this selective feeding and associated lack of recruitment, the current size distribution of trees is strongly skewed towards older trees, likely to be more susceptible to die-off should environmental conditions change significantly. The cause of this change in foraging is unclear. Elephant density has not increased nor has their been any significant hydroclimatic variation since the early 1980's. Subtle shifts in resource use patterns, possibly triggered by prior human-associated disturbance (primarily poaching), may be responsible for the observed decline in tree survival and recruitment. In combination with proposed hydrologic alterations of the Hoanib River associated with agricultural developments, this skewed age structure could result in a massive die-off of Faidherbia trees along the lower river.

Publisher:
Virginia Polytechnic Institute and State University
Type:
Doctor of Philosophy in Biology
Item Type:
Thesis
Language:
en
Files: