Invasive Alien Species in Kruger National Park: Control Efforts since the 1980s
In 1985 ten species were thought to have been successfully eradicated, with the eradication of a further 14 species considered possible. However, one of these plants was again found in Skukuza as recently as 1998, 17 years after its ‘eradication’, thus illustrating that ongoing control efforts are often needed for many years. Whether failure to eradicate these species was due to re-introduction of the species from external sources, the germination of seeds that had remained dormant for many years, or a lack of continuity in control efforts, is not documented. Eradication is however highly difficult to achieve under any scenario.
The first pollution control officer, who had the task of alien plant control and waste management in KNP, was appointed in 1981. From 1982 until 1995, IAP control was conducted by the KNP alien plant clearing team of about 10 people, with assistance from ranger’s teams for specific projects. Work performance was measured by recording the number of IAP stems removed (focusing mainly on L. camara and O. stricta) and although a coarse estimate, 6 889 515 plants were controlled. Between 1996 and 1999, a further 8 579 314 plants were removed by mechanical and herbicide applications. During the period 1996 and 2000 the first use of Geographic Information System technology captured the extent of clearing operations, which amounted to approximately, 92 688 hectares. This is only 16 % of the 590 295 hectares of IAP infestation, with most of the areas constituting follow-up control. Although these areas are small they are essential to the long-term success of the initial control work.
In 1997 the National Working for Water (WFW) programme launched its first project in the KNP, boosting the KNP alien plant programmes significantly. Between 2002/2003 and 2018/2019, Working for Water invested a total of about R174.95 million in alien plant control in KNP. Generally, invasive plant population abundances are now nearing maintenance levels, with annual follow-up operations implemented. However, should these follow-up operations lapse, the system will revert to its former densely invaded state.

Successful control of lantana. Following the control of the dense thickets, grasses and other herbs started regrowing.

Impenetrable thickets of lantana (Lantana camara) along the Sabie River in the 1980s.

Working for Water clearing a dense thicket of a variety of alien plants along the Crocodile River in 1999.