Piosphere effects by elephants vary at local and landscape scales in Chobe National Park, Botswana

Background/Question/Methods

The piosphere effect describes a gradient of vegetation degradation that increases with proximity to water due to herbivore effects. Understanding and monitoring these effects is an important part of management in semi-arid systems. The African elephant (Loxodonta africana) is a prime contributor to piosphere effects due to its water-dependency and large size. We assess how vegetation degradation by elephants varies with distance to water in Chobe National Park, home to one of the largest elephant populations in Africa. Elephant utilization of vegetation was evaluated in thirty-four vegetation plots spanning over 60 km heading inland from the Chobe River.

Results/Conclusions

Regression analysis suggests that patterns differ between local and landscape scales. Branch utilization by elephants follows piosphere predictions at local scales. At landscape scales, branch herbivory initially follows piosphere predictions but then increases beyond the highly utilized riverfront section. Debarking at landscape scales linearly decreases with distance from river, fitting piosphere predictions but extending far beyond distances previously recognized in the literature. At local scales, debarking initially declines with distance to water but then increases beyond about 3 km. These varying patterns between debarking and branch utilization are suggested to relate to seasonal shifts in elephant diet and distribution in the park. They emphasize the importance of monitoring vegetation beyond a “zone of sacrifice” near water and of considering multiple types of vegetation utilization, as these may show divergent trends.