Alien plants in South Africa, especially in dense stands along rivers, use more water than indigenous vegetation. This translates into a 4% reduction in water availability, which could escalate exponentially if these plants were to spread uncontrolled. Further negative side effects of uncontrolled alien plant growth include the loss of rare species, displacement of indigenous populations, increased fire intensity, soil erosion, interception of catchment runoff and downstream impacts on biodiversity and the functioning of aquatic ecosystems. In order to promote the resilience of tributaries in the Upper Breede River as ecological corridors and providers of ecosystem services, critical interventions such as alien clearing and rehabilitation projects are essential. Ecosystem services are recognized as critical to society and of significant economic value. The benefits of restoring natural capital will improve water security, dilute pollution, recharge groundwater and support ecological resilience. Alien clearing and rehabilitation projects of this nature in the Upper Breede River region are essential for the restoration of natural capital.
Due to the invasion of woody alien plants and the subsequent unnatural fire regimes, many of the majestic indigenous trees and shrubs that first populated the forested banks of the Breede River such as the Breede River Yellow Wood (Podocarpus elongatus), Wild Olive (Olea europaea subsp. africana) and Wild Almond (Brabejum stellatifolium) and Palmiet (Prionium serratum) to name but a few, has all but disappeared from the system. The project aims to grow these plants in the Worcester Field Reserve nursery in order to reintroduce them to the system. The reintroductions happen as part of the structured project, but also by means of the landowners who purchase the plants and establish them in their campsites on the riverbanks. The reintroductions of these indigenous trees provide a level of competition for returning alien plants and it improves the functional diversity of the riparian zone. Without this active intervention, the system will not be able to reach the level of ecological resilience required to persevere on its own. There are few places where these trees are cultivated today and without a concerted effort to re-establish them, they will not be able to return to the system.
