Euston-Brown, D., Rathogwa, N & Richardson ... - DWA Home Page

2. Introduction
Mesic Savannas and sweet grassveld are found in the summer-rainfall region in the northeastern part
of South Africa and are part of the Savanna biome. The two alien invasive plants Chromolaena odorata
and Lantana camara, both originating in tropical and subtropical America, are common and abundant
invaders in these systems.
The Working for Water Programme (hereafter WfW), the national organization responsible for
managing invasive alien plants, has experienced major difficulties in controlling these two invasive
plant species in particular. In many cases, the same or other invasive plant species rapidly reinvaded
sites treated to control these species. These invasive species also pose major challenges to managers
in other parts of the world where they are invasive. A study was commissioned by WfW with the aim
of providing managers with guidelines and tools to enable them to choose the best available clearing
methods in a range of habitats.
To do this we used a multi-faceted approach that included a review of international literature, field
studies, and informal interviews with managers and experts in this field. The assimilation, analysis
and processing of all this information was then used to develop some basic tools for choosing the best
management approach for dealing with these species in a variety of situations.
2.1 Terms of Reference
The project aims to provide an overview of the effectiveness of existing clearing methods for major
invasive species in South African mesic savanna and sweet grassveld ecosystems. The degree to which
ecosystems are able to recover after clearing will be assessed, taking into account the dominant alien
species, the duration and density of invasion, features of the ecosystem and indigenous vegetation
that affect recovery (such as soil stability and indigenous seed pools). Based on its findings the project
will develop protocols that will enable land managers and Working for Water managers to select the
best approach to clearing invasive plants. This will include appropriate combinations of mechanical,
chemical and biological control based on the ecological features of the site. Protocols will also be
developed for follow-up clearing for various habitats and invasive plants.
The project’s terms of reference established by WfW are as follows:
• Provide an overview of the effectiveness of clearing methods (mechanical, chemical and biological)
currently used for major invasive species in South African mesic savanna and sweet grassveld
ecosystems. The species should include lantana (Lantana camara) and triffid weed (Chromolaena
odorata), and any other emerging species such as pom-pom weed (Campuloclinium macrocephalum)
identified as important by Working for Water management staff;
• The input from WfW Operational staff will be sought during the research design phase as well
as through the monitoring phase, to ensure interaction between the research team and the
Operations staff.
Development of a clearing protocol based on ecological criteria for Mesic Savannas and Sweet Grassveld for the Working for Water Programme