IntroductionInvasive alien species are disrupting and modifying the normal ecological functions of biomes, ecosystems, and the biosphere as a whole (CBD, 2009). They pose a threat to biodiversity and can cause damage or even eradicate native species on which natural cycles and other organisms depend. As they disrupt energy flow, food chains, and profoundly shake the structure of ecosystems, invasive species create not only ecological problems, but also a host of social, economic, and health problems that affect the livelihoods of nearly every organism 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 alien (non-native) to an ecosystem, which may cause economic, ecological or adverse health effects on native species and/or humans. The roots of these problems all stem from the massive negative ecological impact these organisms are having on the environment (CBD, 2009). For all animal extinctions for which the cause has been known since 1600, invasive alien species have been a determining factor in 40% of cases (CBD, 2006); the second factor contributing to extinctions after habitat loss (GC, 2013). By eliminating native species through competition for resources, predation, and disease transmission, invasive species continue to reduce biodiversity in nearly all ecosystems around the world (CBD, 2009). In the future, this problem could get worse, 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 an area and therefore spread. ..... middle of the paper ...... t of an invasive species is when it begins to displace or even eliminate native species. This can quickly turn into a much larger negative ecological effect. A hierarchy is a useful way to demonstrate the impacts of an invasive species on an ecosystem as it progresses and becomes dominant (Meinesz, 2003). At the first level, when foreign, but previously non-invasive species are first introduced into a new area, the new species can play a role in a previously dissatisfied community; it could fill a vacant niche in the ecosystem. Originally this new species can be seen as a useful contribution to its new environment because it has only (temporarily) increased biodiversity in the area (Meinesz, 2003). At the second level, introduced species begin to reproduce faster than other native species around. It. It also competes with native species for resources