Climate modelling suggests a review of the legal status of Brazilian pepper Schinus terebinthifolia in South Africa is required

Abstract

Brazilian pepper (Schinus terebinthifolia) is a tree native to subtropical South America that was introduced into South Africa in the early 1900s as an ornamental plant. The tree has since escaped cultivation and has invaded ruderal and pristine habitats along the eastern coast of South Africa. Brazilian Pepper is also one of the most problematic invasive alien plants in Florida, USA. We modelled the climatically suitable area for this species in South Africa using MaxEnt, with five distinct datasets: incorporating both the native and the invaded range of the species, as well as different backgrounds. Data sets included: only the South African invasive range distribution points (SA-model); South African invasive range distribution points and Koppen-Geiger climate regions representative in South Africa set as the model background (SA, KG model); only the invaded range distribution points in South Africa and Florida (SA, Fl model); (d) the native range and invaded range distribution points in South African, Florida and South America (SA, Fl, SAm model); (e) only the native range distribution points (SAm model). To quantify overfitting and model performance, we evaluated the area under curve (AUC) and omission rates of the models. Models calibrated with both native and invaded range data projected larger areas (> 60,000 km2) of South Africa to be suitable to the plant when compared to when just the native range data were used to calibrate the model (29,677 km2). Model background influence the potential distribution in South Africa. Our results suggest that the species may have undergone a climatic niche extension in South Africa. Importantly the models suggested that Brazilian pepper has not yet reached its full potential distribution in South Africa and may spread into the Western Cape Province of South Africa, where the plant is currently not listed under the country's invasive species regulations. We recommend a change in the South African legislation in an attempt to pre-empt the potential invasion of this damaging invasive species into the Western Cape Province where it is not yet widespread.