IntroductionInvasive alien species disrupt and modify the normal ecological functions of biomes, ecosystems, and the biosphere as a whole (CBD, 2009). They pose a threat to biodiversity and can damage or even eradicate native species on which natural cycles and other organisms depend. By disrupting energy flows and food chains and undermining the structure of ecosystems, invasive species create not only ecological problems, but also a range of social, economic and health problems that affect the livelihoods of almost everyone organisms on earth, including humans (CBD, 2009). Invasive species (also known as invasive alien species or simply alien species) are defined as any organism (plant, animal, pathogen or other living thing) that is foreign (non-native) to an ecosystem. , which may have adverse economic, ecological or health effects for native species and/or humans. The roots of these problems all stem from the massive negative ecological impact these organisms have on the environment (CBD, 2009). For all animal extinctions with a known cause since the 1600s, invasive alien species have been a contributing factor in 40% of cases (CBD, 2006); the second driver of extinction after habitat loss (GC, 2013). By eliminating native species through competition for resources, predation and disease transmission, invasive species continue to reduce biodiversity in almost all ecosystems around the world (CBD, 2009). In the future, this problem could worsen and, if no action is taken, it could lead to a cascading ecological problem so large that entire communities, or even ecosystems, could collapse. Causes Invasive alien species are not native to a region and can therefore spread. ..... middle of paper ......the beginning of an invasive species is when it begins to displace or even eliminate native species. This can quickly lead to a much greater negative ecological effect. A hierarchy is a useful way to demonstrate the impacts of an invasive species on an ecosystem as it advances and becomes dominant (Meinesz, 2003). At the first level, when a foreign, but previously non-invasive, species is first introduced to a new area. , the new species could play a role in a community that was not previously fulfilled; this can fill a vacant niche in the ecosystem. Originally, this new species can be considered a useful contributor to its new environment because it only (temporarily) increased biodiversity in the region (Meinesz, 2003). At the second level, the introduced species begins to reproduce more quickly than other native species in the surrounding area. he. It also outcompetes native species for resources