Invasive Alien Species

Invasive alien plants
Plants colonization is a natural phenomenon which humans have accelerated by international travels, deliberately or neglectfully transporting plant species. Invasive alien plant species (IAPS) usually cause the modification of the indigenous ecosystems through their invasive expansion. The expansion is facilitated by the propagule pressure brought about through human globalization and the IAPS competitive advantage over the native fauna (Keane and Crawley 2002; Leung et al. 2004).
The competitive advantage is facilitated through habitats vulnerability (due to global climate change, overgrazing and localized nutrient enrichment), different evolutionary histories and the lack of natural enemies in the new habitat (Mack 1989; Antonio et al. 1992, Mack et al. 2000; Keane and Crawley 2002). As a result, plant invasion has been identified as a major threat to the biodiversity of natural habitats (Vitousek et al. 1997). The major concerns are habitat space, ecosystem services and biodiversity (Auld and Medd 1987; Mooney 2005). Approximately 10 million ha of South Africa and Lesotho have been invaded by IAPS (Le Maitre et al. 2000). These cost of these invasions are best documented in the fynbos ecosystem due to its high value and detailed research (Wilgen et al. 2001). Invasions into the Fynbos ecosystem have been estimated to reduce its value by more than US$11.75 billion (Wilgen et al. 2001). Additionally, forest hydrology have estimated alien invasive