Invasive Species

Invasive Species — page 3 — The Australian government built the world’s longest fence to try to keep rabbits and dingoes from spreading It is 3,488 miles 5,614 km long 6

Invasive Species — page 4 — home The rabbits quickly spread They have few predators in Australia and they reproduce quickly By the 1920s there were approximately 10 billion bunnies in Australia 2 The rabbits ate so much vegetation that native species such as wallabies and rat kangaroos did not have enough food So the bunny battle began In 1907 the government tried building three long fences to keep rabbits from spreading to other parts of the country But it was too late The bunnies had already moved in Later cats and foxes were introduced to eat the rabbits They ate some rabbits but they ate native species too causing even more stress to these species ARE INVASIVE SPECIES BAD Invasive species are not invasive everywhere In their native habitats they usually do not cause problems and may not even be very common Their natural predators competitors parasites and diseases keep them in check Invasive species only become destructive when they arrive in a new place away from these checks and balances In 1950 scientists hit on a method of biocontrol the use of organisms to control pests They introduced a rabbit virus that causes a disease called myxomatosis The disease killed up to 99 percent of the rabbits in some areas 3 However it is spread by mosquitoes which need water to reproduce So the virus was not very effective in areas with a dry climate Over time the virus weakened and some rabbits became resistant to it It started to kill fewer and fewer rabbits The rabbit population increased once again One female rabbit can have up to 30 babies per year 7

Invasive Species — page 5 — PREVENTION IS THE BEST CURE Benjamin Franklin once said An ounce of prevention is worth a pound of cure 4 This wise saying certainly applies to invasive species it is much easier to keep them out than to remove them once they’ve spread It’s also much less expensive One of the best ways to prevent invasions is by teaching gardeners pet owners outdoor enthusiasts and others about ways to keep invasive species from spreading Stronger laws can also keep these species from being transported across state lines or from one country to another In 1995 a virus that causes rabbit calicivirus disease RCD escaped a research laboratory on an island near Australia when flies picked it up and carried it to the mainland The virus spread quickly and the population of rabbits crashed again Recently some endangered small animals have begun to recover thanks to the rabbit decline But only time will tell if this will be a permanent solution Some rabbit populations are already showing signs of resistance to the virus Scientists are studying new deadlier strains of the virus for use in the future Meanwhile the government continues to fight the bunny invasion using poisons traps fences and biocontrols WHAT ARE INVASIVE SPECIES The European rabbit is an example of an invasive species a species that arrives in a new area and causes harm Invasive species can be plants animals fungi or bacteria They may harm the environment other plants or animals or human health Next to habitat loss they are considered the greatest threat to biodiversity in the world Approximately 1 4 trillion dollars are spent globally each year to control invasive species and repair the damage they cause 5 Not every exotic or nonnative species is invasive Many such as farm animals and crop plants are useful to humans People in the United States rely on exotic species such as cattle chickens wheat rice and potatoes for food Others are 8

Invasive Species — page 6 — A female rabbit may have one litter every month used in landscaping or kept as pets Approximately 50,000 exotic species can be found in the United States and of these approximately 4,300 are considered invasive 6 This number is so high because Hawaii has many invasive species Scientists estimate that globally approximately 10 percent of species introduced to a new area will survive and reproduce and only approximately 10 percent of those will become invasive 7 9

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