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When a new species is introduced to an ecosystem, it is called an exotic or alien species. If the introduced species survives, the results can be disastrous. Without any natural predators, it reproduces unchecked.
In Queensland, Australia, sugar cane is one of the main exports. But in 1935, sugar cane was threatened by beetles. Farmers were very concerned. None of the insecticides they tried worked. Finally, the farmers discovered what they believed was the perfect solution – the giant marine toad of Central and South America. This toad loved to eat the sugar cane-eating beetle! The toads did such a good job in Australia, they wiped out all the sugar-cane beetles. The toads were still hungry, so they began to eat native insects, fish, amphibians, ground-nesting birds and small mammals. The toad, renamed the cane toad, has no natural enemies and is poisonous. They are reproducing very fast and it is only a matter of time before they spread all over the north of Australia.
Andrew Hobbs, Australia
The water hyacinth was first spotted floating on a lake in Uganda in 1987. People say this pretty plant came from South America. In ten short years, it has spread like a horror story throughout the lakes and rivers of eastern and southern Africa. It affects the fishing industry by suffocating fish breeding sites. It chokes the water transport system. As it rots, it affects drinking water and smells disgusting. It provides a breeding site for mosquitoes that carry malaria, snails that bring bilharzia and snakes that bite. The weed also creeps into hydro-electric plants, wrapping itself around the turbines like some fairy-tale beanstalk. Pulling the weed out by hand is impossible: you need a crane, and snakes and insects tumble out with it. Horrible! The best chance of defeating the water hyacinth is perhaps a little beetle that eats the weed. Field trials using the beetle are being done in Uganda right now.
Jean Agnes Lutaya, Uganda
In Lake Victoria in Africa, 60% of the native fish species have become extinct due to the introduction of the Nile perch. The perch eats smaller fish and upsets the fragile ecosystem.
Mutyaba Andrew Kagwa, Uganda
Humans, once considered to be the only creatures wise enough to alter the environment for our convenience, have turned out to be the only ones insane enough to demolish it.
Robert Oburta Wanndera, Uganda