However, on the southern coastlines, loss of mussel Perna perna's habitat has not been as extensive to the competing Mediterranean native mussel Mytilis galloprovincialis.
On land, acacia species have been most detrimental to the bioregion, as their land usage expands rapidly. Mature acacias proliferate their seeds and access huge expanses of land. The acacia species Acacia dealbata, Acacia mearnsii, Acacia longifolia, Acacia baileyana, Acacia decurrens, and Acacia Cyclops have overtaken more indigenous species, by changing soil nutrition and taking habitat. The difficulty in controlling acacias is problematic due to the community's use of many acacia species as kindling. Likewise, acacia species stabilise the soil; indeed they were introduced by agriculturalists for the very reason. While having stabilized the soil, they've encroached on the South African fynbos vegetation. At the same time, the increased agricultural usage of the land has hindered the nesting habits of the bird species Black Harriet Circus maurus. In order to counter the multiple problems associated with the acacia encroachment, researchers searched for natural enemy wasps of the Bruchophagus line, specifically Bruchophagus acaciae, Bruchophagus orarius, and Bruchophagus interior, with the purpose of hindering acacia seed proliferation.
The acacia has not been the only species introduced for the purpose of stabilizing the soil. Marram grasses were introduced in order to stabilise shifting sand dunes that flooded the South African plains and made agriculture difficult. The Marram grass Amophilia arenaria has been praised for its ability to provide an amiable habitat for the native species of the area. Due to the complexity of alien species and their influences to the diversity of native flora and fauna, investigations and attempts have been made to counteract the process, or at very least, record it.
South African Biodiversity
Biodiversity along the Southern African shorelines is unique in that its species have evolved and thrived due to the confluence of two distinct water masses. The Agulhas current flows alongside the eastern shores of South Africa, while the west coast is characterised by colder deeper waters (Peschack, 2005). The flora and fauna that immigrant settlers found here is one of the most specific in the world. In southern Africa, 12% of plant species are endemic (Willis et al. 1996, in Mehta 2000).Moreover, the floristic region of the Cape is one of only six on Earth (Branch, 2005). The importance of maintaining the integrity of South African Cape ecosystem cannot be understated.
However, many invasive species have invaded the bioregion and caused concern, beginning in the 1700s. At this time, immigrant settlements that came to South Africa began practises of irrigation and livestock raising that negatively affected soil nutrition and made the soil thinner. Consequently, native vegetation species diminished due to poor soil quality (Mehta, 2000). That trend has continued and become multifaceted, affecting both land and ocean species.
Negative Impacts of Alien Species on Land
Indeed, the most widely studied intruders on the South African Cape