Alien trees, shrubs and creepers invading indigenous vegetation in the Hluhluwe-Umfolozi Game Reserve Complex in Natal

Abstract

The results of a survey and monitoring programme conducted in the Hluhluwe-Umfolozi Game Reserve Complex in Natal are presented. The area consists of 900 km2  of savanna and forest vegetation.

Twenty alien tree, shrub and creeper species currently invading indigenous vegetation within the Complex are listed. Herbaceous aliens were not surveyed.

An analysis of the habitats being invaded by these alien plants is presented and it is concluded that riverine and forest-edge habitats are those most seriously threatened by alien plant infestations.

The distribution, nature and history of the infestations of each species are summarized. Distribution maps given for the eight species which are currently most important in the Complex. The potential threat posed by each species is estimated and the species are ranked in order of priority for control action.

The South American composite, Chromolaena (Eupatorium) odorata, is identified as being the alien species currently posing the greatest threat to natural vegetation in the Complex. The Asian tree, Melia azedarach, is considered the second most important alien species invading the area. It is concluded that both these species should be declared noxious weeds throughout the Republic and that research into their biological control is urgently required.