Assessing the level of compliance with alien plant regulations in a large African protected area

Regulations provide the legal basis for managing biological invasions, but assessments of their effectiveness are rare. To assess the influence of national and local regulations on alien plant species richness and composition in a large protected area (Kruger National Park; KNP; South Africa) we surveyed tourist camps and staff villages for alien ornamental plants. We compared our survey results in 2020 with a previous survey carried out between 1999 and 2003, in the context of national regulations on alien plants promulgated in 2001 and 2014. The number of alien plant species recorded in KNP has almost doubled since the first survey (231 to 438), although there has been significant species turnover (93% average replacement across all camps). Importantly, however, both the number of recorded listed and regulated alien plant species found in KNP, and their species richness per camp, have declined (by 38% overall and by 56% per camp). This suggests that regulations are effective. In contrast, the number of recorded unregulated ornamental alien species recorded has increased (by 157% overall), but this likely partly due to an increase in survey effort. Alien species regulations provide clear guidance for conservation managers, and there are promising signs of their effectiveness in directing management in KNP. However, converting alien species lists into priorities for control or regulation will continue to require risk analyses sensitive to park user needs. We advocate for better regulation effectiveness monitoring, and for such monitoring results to be interpreted based on local management needs and concerns.