Foreign or alien invaders to the islands are the major cause of Hawaii's species becoming endangered. Long ago, the Polynesians brought domestic animals like the dogs, pigs, and chickens. These animals harmed endemic (native) birds and other small species. The polynesians destroyed many of the native species' habitats by clearing forests to grow crops and to build their homes.
The animal that is doing the most harm to our native species and rainforest is the feral pig that is closely linked to the European boars. They have destroyed many of the native species' habitats and the creatures that depended on them. These feral (wild) pigs crush, eat, and uproot plants. They gnaw at the roots of the plants causing the plants and trees to die. When the trees die, the dirt has nothing to keep it in place. When there is heavy rainfall, the dirt slides and the land starts to erode. Our rivers, streams, lakes, and ocean become polluted from the dirt that rolls down the hills. The feral pigs also wallow (roll around in mud) in the forest ground which become a perfect place for mosquitos to breed in.
The mosquitos is also a threat to our native birds, especially the Hawaiian Honeycreepers, apapane, by transmitting a disease called Avian (bird) Malaria.
The mongoose and the rats were introduced by the Europeans and have caused harm to our native species. The mongoose were purposely brought in to kill off the rats in the sugar cane fields. Unfortunately, they didn't study them well enough, and their plan failed because the mongoose sleeps in the night and hunts in the day, and the rat sleeps in the day and hunts in the night, so they never met. Therefore, in order to survive, the mongoose and the rats are doing harm to our native species by harming the ground nesting birds such as the Hawaii's state bird, the Nene goose..
The exotic plants that were once cherished for their beauty are a threat to our native plants. Plants such as the South American banana poka are vines that kill native plants in Hawaii's rainforest by suffocating them. They block out their oxygen and sunshine. As the vines kill the trees and let in too much light, like a chain reaction, the second and third layers in the rainforest are also harmed. Recently, another plant invader from South America that is considered as one of the most dangerous threats to Hawaii's ecosystems is the miconia. In Tahiti it is called "the brown tree snake of the plant world" because it can choke out many native plants.
Foreign invaders such as the goats and the Argentine Ants also contributed in causing our famous Silversword to become endangered. Many years ago people thought the Silversword was snow on Haleakala (inactive volcano) located on the island of Maui. The feral goats which were brought in as a source of food by the Europeans have turned many of the endangered Silverswords into stumps by crushing and eating them. The Argentine ant is a new and deadly foe to Hawaii's Silversword. They eat the larvae of the native yellow-faced bees, important pollinators of the Silversword. Without the bees to pollinate the Silversword, it won't be able to produce seeds.
People today are also responsible for the decline of our native species. People are polluting our environment which is causing harm to our native species' habitats. Irresponsible people smuggle in illegal reptiles such as iguanas, alligators, and snakes which are turned loose into the wild when they are too big or too hard to take care of. These pets then become predators of our native species and disturb nestlings of native birds. Also people invade the ocean and beaches that use to be breeding grounds for Green Sea Turtles, Humpback Whales, and the Hawaiian Monk Seals.
Read more about foreign invader:
The Alien Species Problem in Hawaii - http://www.hear.org/#theproblem
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