The management dilemma: Removing elephants to save large trees

Abstract

The loss of large trees ( 5 m in height) in Africa’s protected areas is often attributed to the impact by savanna elephants (Loxodonta africana). Concerns have been raised over large tree mortality levels in protected areas such as South Africa’s Kruger National Park (KNP) and in the past, the need to manage its elephant population in order to preserve large trees and biodiversity as a whole. Our review aims to synthesise and discuss the complexities of managing elephants’ effects on the landscape to ensure the survival of large trees, as well as the application purposes of the various lethal and non-lethal elephant mitigation strategies. We further critically evaluate past management strategies, which have solely focused on controlling elephant numbers to protect large trees. Past mitigation strategies focused on managing elephant impact by directly reducing elephant numbers. However, maintaining elephant numbers at a pre-determined carrying capacity level did not prevent the loss of large trees. Research on large tree survival in African savannas has continually exposed the complexity of the situation, as large tree survival is influenced at various demographic stages. In some cases, a coalescence of historical factors may have resulted in what could be perceived as an aesthetically appealing savanna for managers and tourists alike. Furthermore, the past high density of surface water within the KNP homogenised elephant impact on large trees by increasing the encounter rate between elephants and large trees. Our review evaluates how current mitigation strategies have shifted from purely managing elephant numbers to managing elephant distribution across impact gradients, thereby promoting heterogeneity within the system. Additionally, we discuss each mitigation strategy’s occurrence at various landscape scales and its advantages and disadvantages when used to manage impact of elephant on large trees.Conservation implications: A variety of options exist to manage the effects that elephants have on large trees. These options range from large-scale landscape manipulation solutions to small-scale individual tree protection methods. Interactions between elephants and large trees are complex, however, and conservation managers need to consider the advantages and disadvantages of each mitigation strategy to protect large trees.

Conservation Genetic Assessment of Savannah Elephants (Loxodonta africana) in the Greater Kruger Biosphere, South Africa

“…Each individual’s age was estimated [33]. IDs were given to every individual based on ear and tusk characteristics observed in photographic evidence [34].…”

The African Elephant (<i>Loxodonta africana</i>): Mini-Review of an Endangered Species

“…The restoration of the environment must always be carefully considered. Interference in ecological processes may be necessary but in effective cases of degradation of the landscape; conservation strategies should consider protecting large trees, but never forgetting ethical approaches to elephant populations [125].…”

Heterogeneity in African savanna elephant distributions and their impacts on trees in Kruger National Park, South Africa

“…However, debate continues as to the real threat posed by elephants to trees and biodiversity overall in savannas (Coverdale et al., 2016; Guldemond et al., 2017; Henley & Cook, 2019). This debate is exacerbated by general uncertainty about what underlies heterogeneity both in elephant density and in how their impacts are distributed in savanna landscapes, which can vary dramatically in space (Anderson & Walker, 1974; Codron et al., 2006).…”