Anh Nguyen When it comes to rabbit, people might just imagine an adorable and furry “ball”, chewing berries and hopping around. Yet, not many, probably most outsiders of Australasia, ever consider that this diminutive species is harming the environment indeed, especially in Australia. PICTURE 1. Bunnies in 3D Crush Café (taken by author)
How rabbits appeared in Australia Australian rabbits have their origin in Europe (Oryctolagus cuniculus), which were first introduced into the region in early 19th century. The first feral colony were brought by the First Fleet to Tasmania as provisions by 1827. Following that, in 1859, Thomas Austin – a landowner in Winchelsea, Victoria, released 24 wild rabbits imported from England with a view to proceeding his hunting hobby as well as helping other settlers feel comfortable. This incident was the root of all detrimental impacts rabbits would cause on the fragile ecology in the future. They accelerated in population, spreading to the Queensland – New South Wales border by 1886 and reached to Western Australia as well as the Northern Territory by 1900. Rabbits had covered 4 million square kilometers of Australia in just a few decades. Today, rabbits are distributed relatively equally throughout the country, except for the northernmost areas. Why rabbit population escalates Insufficient quantity of predators coupled with ideal conditions smoothed the path for the rodents to do their best job – breeding. The tropical climate of Australia is one of the main factors contributing to rabbit increase. With mild winters, they can breed all year round. In addition, humans’ sprawling agriculture resulted in vast areas with low vegetation, which are ideal habitat for feral rabbits. What is more, before rabbits arrived in the country, red foxes and feral cats were regarded as invasive mammalian predators to native wildlife and farming. Hence, the government responded to these hindrances by culling them. This, in fact, caused a boomerang effect. Let’s take Macquarie Island as an example. When the rabbits and cats were introduced into Australia, they formed a perfect predator-prey relationship. However, that relationship was interrupted by a rabbit-killing virus. The cats turned to eating a great deal of native birds when rabbit numbers decreased. The locals then decided to wipe out the cats. Thus, between 1985 and 2001, felines no longer existed on the island. Birds were not in danger anymore, and so were the rabbits, which fortunately survived from the virus. Their population boomed again! Rabbits’ effects and the Australians’ solutions Excessive grazing of rabbits leaves the soil empty with no vegetative covers, allowing the wind to erode the top fertile soil away. Soil erosion leads to water absorption and the vegetation reproduction. In addition, agricultural run-off and salinity of soil are also likely to occur when top soil is diminished. Rabbit warrens contribute to soil degradation as their burrowing disturbs the soil and damages the flora. As consequences, some plant species go extinct, which also leads to decrease in native birds, mammals or insects that feed on them and use them as shelter. The Australian livestock is in danger as well, since they have to compete with rabbits for available pasture. Feral rabbits have hindered both the economic growth and nature development of Australia. The latter issue is much more severe; the outcomes cannot be compensated. Around much of 19th century, human tried to control the rabbits by trapping and shooting. Hunting them for sports or food just makes a drop in the ocean compared to their exponential growth. To early 20th century, the government decided to establish rabbit-proof fences to protect the farming regions in Western Australia. However, the plan was unsuccessful as multitude of rabbits invaded the land during the construction. Some could even have dug through the fences. The government went on with the biological control measurement. In 1950, they experimented a virus to kill the feral rabbits. The virus was myxomatosis, carried by the fleas and mosquitoes into the wild. This time, it first brought some considerable achievements, as about 90% of rabbits was wiped out, but not continued any longer. The fleas and mosquitoes were not able to exist in arid areas, so some rabbits survived, and they went on reproducing. The survivals and their successors developed natural genetic immunity to the virus. The same happened to RHD, which was released in 1995. In 2011, a new rabbit eradication program comprised of three stages was implemented. Another virus, rabbit calicivirus, was released. Then 307 tons of brodifacoum baits was dropped for rabbits that survived from virus. Poisons were used later to kill ones that survived from both virus and baits. Even so, the rabbits went on existing because of coevolution between the virus and the host. Biological controls are never enough, plus they literally affect the whole nature. Many species die because of eating poisoned baits or poisoned bodies of dead rabbits. A considerable amount of vegetation dieback was possibly resulted from hazardous chemicals released into the environment. Future eradications of rabbits are still in the process of completing, yet it also needs cooperating with other protection programs such as preservation of on-ground threatened flora and fauna, controlling other invasive animals work as rabbit predators, to name but a few. The control should not only focus on one species but the whole ecosystem. Humans should learn from the mistakes in the past that, the nature is an integrated system, so when one part is affected the whole “machine” is drastically under the impacts as well. After all, it was not the rabbits’ responsibility for ruining the environment from the beginning; it was because of the human’s egocentric satisfaction. References Office of Environment & Heritage. 2015. Rabbits – Fact sheet. NSW Government. Read 18.11.2017. http://www.environment.nsw.gov.au/pestsweeds/RabbitFactsheet.htm Ypte. Rabbit: Oryctolagus cuniculus. Young People's Trust For the Environment. Read 18.11.2017. http://ypte.org.uk/factsheets/rabbit/overview#section Wendy Zukerman, ABC Science. 08.04.2009. Australia's battle with the bunny. ABC. Read 18.11.2017. http://www.abc.net.au/science/articles/2009/04/08/2538860.htm The Conversation. 12.06.2015. Killing cats, rats and foxes is no silver bullet for saving wildlife. The Conversation Trust (UK) Limited. Read 18.11.2017. https://theconversation.com/killing-cats-rats-and-foxes-is-no-silver-bullet-for-saving-wildlife-42754 |
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May 2019
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