Alien species can have massive impacts on native biodiversity and ecosystem functioning. Assessing which species from currently cultivated alien floras may escape into the wild and naturalize is hence essential for ecosystem management and biodiversity conservation. Climate change has promoted the naturalization of many alien plants in temperate regions, but whether outcomes are similar in (sub)tropical areas is insufficiently known. In this study, we used species distribution models to evaluate the current naturalization risk of 1,527 cultivated alien plants in 10 countries of Southern Africa and how their invasion risk might change due to climate change. We assessed changes in climatic suitability across the different biomes of Southern Africa. Moreover, we assessed whether climatic suitability for cultivated alien plants varied with their naturalization status and native origin. The results of our study indicate that a significant proportion (53.9%) of the species are projected to lack suitable climatic conditions in Southern Africa, both currently and in the future. Based on the current climate conditions, 10.0% of Southern Africa is identified as an invasion hotspot (here defined as the top 10% of grid cells that provide suitable climatic conditions to the highest numbers of species). This percentage is expected to decrease slightly to 7.1% under moderate future climate change and shrink considerably to 2.0% under the worst-case scenario. This decline in climatic suitability is observed across most native origins, particularly under the worst-case climate change scenario. Our findings indicate that climate change is likely to have an opposing effect on the naturalization of currently cultivated average plants in (sub)tropical Southern Africa compared to colder regions. Specifically, the risk of these plants’ naturalizing is expected to decrease due to the region’s increasingly hot and dry climate, which will be challenging for the persistence of both native and alien plant species.

1. Ongoing intensification and fragmentation of European agricultural landscapes dramatically reduce biodiversity and associated functions. To sustain ecosystem services such as ant mediated pest control, the enhancement of perennial non-crop areas holds great potential. 2. To study the potential of newly established grasslands to enhance ant diversity and associated functions, we used hand collection data to investigate differences in ant community composition (a) between cereal crops, old grasslands, and new grassland transects of three years age; (b) depending on ant functional traits; and linked to (c) natural pest control services quantified through predation experiments. 3. Ant species richness did not significantly differ between new and old grasslands, but was significantly higher in grasslands compared to cereal crops. Contrary, ant community composition of new grasslands was more similar to cereal crops and distinct from the species-pool of old grasslands. The functional trait space covered by the ant communities overlapped between old and new grasslands but was extended in the old grasslands. Pest control did not differ significantly between habitat types, and therefore could not be linked to the prevalence of functional traits related to biocontrol services in new grasslands. 4. Our findings show trends of convergence between old and new grasslands, but also indicate that enhancing ant diversity through newly established grasslands takes longer than three years to provide comparable biodiversity and functions. 5. Synthesis and applications Newly established grasslands can increase ant species richness, abundance, and pest control in agroecosystems. However, three years after establishment, new grasslands were still dominated by common agrobiont ant species and lacked habitat specialists present in old grasslands, who require a constant supply of food resources and long colonization times. New grasslands represent a promising measure for enhancing agricultural landscapes but must be preserved in the longer term to sustain biodiversity and associated ecosystem services.