Scientific Services

In the long-term success of any invasive alien plant control programme, recognition and management of the main pathways of dispersal is critical. Other than the use of alien plants for ornamental purposes, which was shown to be the main introduction pathway into Kruger National Park (KNP) in the past, the invasion of riparian habitats is directly linked to the extensive invasions in the KNP’s catchments. The main rivers flowing into the KNP originate several hundred kilometres away from the park, and only a relatively small portion are under the direct management of the park.

A map showing the main rivers flowing into the Kruger National Park. The rivers originate in the high lying areas to the west of the park, flowing through the park and into Mozambique. © S MacFadyen

While ornamental plant use can be more easily managed, large numbers of species and the high density of these species in the catchment of the rivers flowing into the KNP will result in ongoing pressure by seeds spreading into the park. With the increase in development in the Lowveld and escarpment areas, including urban areas, commercial farming and forestry, the catchments of all rivers entering the KNP have been invaded by a wide range of species, complicating IAP control efforts. In 2007 a study showed that of 185 riparian species of major concern in the upper catchment, 88 occurred inside the KNP. This illustrates the importance of collaborative and landscape scale programmes being required to successfully manage invasive alien plants across the river catchment. Another study showed how the number of ways by which a species can invade leads to the larger number of potential impacts the species may have on the system. Therefore if the threats and potential negative impacts are to be minimised, careful prioritisation and management of the most important pathways of invasion is necessary.

Parthenium (Parthenium hysterophorus) spreading along the Crocodile River.

Conclusion

The series of short has provided a brief overview of invasive alien species in KNP. Managing alien species is a large and growing challenge, the complexity of which is increased by the size of KNP, the vast area of the catchments draining into the KNP, number of camps and staff living in the KNP, the length of rivers that require managing, as well as the difficult and dangerous conditions in working along the KNPs Rivers. However, from the first records of ‘troublesome weeds’ and concerns raised in the 1930s, KNP has advanced in its approach and the scale of efforts to manage invasive alien species has grown substantially. The challenge is to continue to maintain the gains made and respond speedily to new threats as they appear.