Today, plants and animals can usually travel around the world in a matter of hours or days via planes or ships. Their presence is usually harmful, but some scientists believe they can actually be a catalyst for biodiversity! Invasive or exotic species have altered the Chesapeake Bay region; with both a negative and positive impact. “Exotic species are plants, animals, or microbes that have been transported from one geographic region to another.” (5) They are moved from an area where their evolutionary equilibrium is established, to an area where they may have no natural competitors. Invasive or exotic species can have a significant impact on our environment. They can put ecosystems at risk by changing an entire environment, displacing other species native to the environment, and even harming human activities such as fishing. (1) Once introduced into a new environment, invasive species compromise the ecological balance of the area. They may have no natural predators and can outcompete natural organisms; giving them the opportunity for rapid growth throughout the environment! (The Nature Conservancy, 2004) Invasive species are also a major reason why some of our endangered species are threatened. The graph on the left shows that approximately 50% of threatened or endangered species are due to these exotic species! In the United States alone there are many invasive and exotic species already established! According to Exotics in the Chesapeake, “At least 4,500 species have established free-living populations in the United States” (3) These species have also appeared in the waters around us! I believe that these invasive and exotic species have even altered the Chesapeake Bay region and that these alterations are not always predictable! For example, oysters in the Chesapeake Bay have suffered since their parasites Dermo and MSX were introduced to the area as exotics.(3) The fundamental role of oysters is to abolish algae in the water; however, with the decline of oysters comes a serious deterioration of the bay's ecosystem. (3) This not only impacts the bay, but also the oyster fishery, resulting in significant economic losses. (3) Other examples include the mute swan; which acts aggressively towards other birds in the area. (2) Although there are many disadvantages of these species, many could bring benefits. The Hydrilla plant could take over and replace other native plants; but it can also benefit the bay.