Effects on Native Biodiversity Biological pest control can potentially have positive and negative effects on biodiversity. Most of the time a  biological pest control is introduced to an area to protect a  native species from an invasive or exotic species that has moved into its area. The control is introduced to lessen the competition among native and invasive species. However, the introduced control does not always only target the intended species. It can also target  native species. When introducing a  biological control to a new area, the amount of testing and research that has been preformed does not matter. It could still potentially harm an unwanted native species. If a species is introduced and attacks a  native species, the biodiversity in that area can decrease dramatically. When one  native species is removed from an area, it may have filled an essential niche, When this niche is absent it will directly affect the entire ecosystem. The cane toad (Bufo marinus) was introduced as a biological control and had significant negative impact on biodiversity. The cane toad was intentionally introduced to Australia to control the cane beetle. When introduced, the cane toad thrived very well and did not only feed on cane beetles but other insects as well. The cane toad soon spread very rapidly, thus taking over native habitat. The introduction of the cane toad also brought foreign disease to native reptiles. This drastically reduced the population of native toads and frogs. “The cane toad also exudes and can squirt poison from the parotoid glands on their shoulders when threatened or handled. This toxin contains a cocktail of chemicals that can kill animals that eat it. Freshwater crocodiles, goannas, tiger snakes, dingos and northern quolls have all died after eating cane toads, as have pet dogs (Cane toad,2003)”. This goes to show a small but deadly organism can alter the native biodiversity in an ecosystem in a very expedient manner. A pyramid effect can take place if  native species are reduced or eradicated. The domino effect keeps on going and can potentially exude on other bordering ecosystems. A second example of a biological control that consequently took over native species was the Rhinocyllus concius. The seed feeding weevil was introduced to North America to control exotic thistles (Musk and Canadian). However, the weevil did not only target the exotic thistles, it also targeted native thistles that are essential to various native insects. The native insects solely rely on native thistles and do not adapt to other plant species. Therefore, they cannot survive. Biological controls do not always have negative impacts on biodiversity (Corry 2000). Successful biological pest control reduces the density of the target species over several years, thus providing the potential for  native species to re-establish. In addition, regeneration and reestablishment programs can aid to the recovery of  native species.  Native species can be affected in a positive way as well. To develop or find a  biological control that exerts control only on the targeted species is a very lengthy process of  research and experiments. In the late 1800’s, the citrus industry was in great fear when the cottony cushion scale was discovered. This organism could cause a great deal of economic loss to the industry. However, a biological control was introduced. The vedalia beetle and a parasitoid fly were introduced to control the pest. Within a few years time, the cottony cushion scale was controlled by the  natural  enemies and the citrus industry suffered little financial loss. Many exotic or  invasive species can suppress the development of  native species, therefore the introduction of an effective  biological control that targets the  invasive species will be reduced, thus allowing the rejuvenation of the  native species. Biological pest controls can reduce competition for biotic and abiotic factors which can result in the re-establishment of the once over ran  native species.