Persistent Effects of Chemicals Used to Control Shrub Densification in Semi-Arid Savanna

Abstract

Mokala National Park (MoNP) was proclaimed in 2007 in an area that used to be managed as a commercial wildlife and hunting farm, and prior to 2003 as a cattle and goat farm. The vegetation comprises sparse to closed woodlands and shrublands of the Savanna Biome. Shrub densification was deemed undesirable in the context of commercial farming where management objectives were to maximise production of grazing animals and to promote visibility of wildlife to tourists and hunters. Accordingly, previous landowners have attempted to eradicate prolific shrubs (particularly Senegalia mellifera) by mechanical and chemical means in certain areas during the period 1996–2004. Effects of these treatments are still apparent more than a decade later. Here we document the history of herbicide applications and other management practices in affected areas of MoNP. We furthermore explore potential ecological effects of the herbicide used (‘Molopo 200GG’ with active ingredient Tebuthiuron) in relation to the ecology of the most-affected shrub species, S. mellifera. We conclude with suggestions for future monitoring to establish potential long-term impacts of the chemical control.