The Orystolagus cuniculus, or the European
Rabbit, is just one example of the detrimental effects that invasive species can
have on their environment. An invasive species is a species that is introduced
into an environment where it is not native. These species can upset an already
established ecosystem, harm natural resources and threaten the ability of
humans to use these resources.
Native to the
Iberian Peninsula, the European Rabbit was first introduced to Australia in
1788, and eventually released into the wild in 1859. A population that started
as a group of 24 rabbits released for hunting purposes quickly multiplied, reaching
a population of about 10 billion by the 1920’s (5). They are now found almost
everywhere across the continent. This species of wild rabbit is still plaguing
Australia years after their first introduction.
These
animals have become such a nuisance that there are organizations devoted to
eradicating the species from the continent, and the government provides
resources to educate its citizens of the problem. Shown above left is a
pamphlet that is distributed by the Australian government’s Bureau of Rural
Sciences to land owners. It provides information on how to recognize and assess
a rabbit infestation as well as what measures should be taken (4). These
pamphlets teach awareness on how large a threat these small creatures can be.
What is it that
makes these seemingly harmless creatures so dangerous? In a risk assessment
done by the Australian government, and the Invasive Species Specialist Group,
the European Rabbit is noted to cause habitat degradation and have negative
effects on local agriculture (3). These rabbits feed on plant life to the point
that they prevent regeneration, and native vegetation cannot be sustained (4).
Even a population with low density can prevent regeneration, leading to soil
erosion. In some cases they have
turned land into semi-desert.
The
picture to the left shows the erosion caused by rabbits in a gully in southern
Australia. Their destruction of vegetation, along with increased competition
for food and shelter, has caused a decrease in populations of similar-sized
native creatures (2). They often steal burrows of native burrowing animals such
as the Bilbies, and their burrows have negatively impacted populations of
seabirds and sea lions (3). Rabbit burrows become death traps for sea lion pups
and disturb the underground nests of certain sea birds (3). They sustain populations of exotic
predators such as feral cats and foxes, increasing predation on native species
while not having a severe impact on the rabbit population (4). Population
control for these animals is extremely difficult due to the rapid rate that
they reproduce. In only a year and a half, one pair of rabbits can multiply
into 184 individuals. The picture to the left demonstrates just how large the
populations can become and the amount of destruction they have on their environment.
The introduction of this rabbit has led to a number of native mammals, and
plant species, to become endangered or extinct.
There have been
numerous efforts to eliminate the rabbit population from Australia, but none
have been entirely successful. Conventional methods, such as using poison and
fire to destroy burrows, are costly and have proven ineffective due to the rate
of reproduction (5). Rabbit fences have also been constructed in attempt at
protecting pastoral and agricultural lands. The most effective methods at
containing rabbit populations have been biological, however even these have had
their problems. Two different viruses have been introduced to the rabbits in
hopes of eliminating the population. The first was the myxomatosis virus that
was released in 1950. It causes skin tumors to form and can lead to a number of
other problems such as secondary bacterial infections. The introduction of the
virus was at first successful and led to a large decrease in population size,
but this did not last. The rabbits began to develop a resistance to the virus
and numbers began to increase again (2). The Rabbit Haemorrhagic Disease virus,
known as RHD, was introduced in 1995. This virus was more effective than
myxomatosis, but again a resistance to the virus is being built (1). Currently
there are multiple research programs in progress looking for new and more
effective ways of keeping the rabbit population in check.
As the rabbit has
negatively impacted the environment, it has also had negative repercussions for
Australia’s economy. It is difficult to estimate just how much the introduction
of the European Rabbit has cost the Australian government or what the total
economic loss has been. Population control is expensive, especially since
rabbits seem to reproduce faster than you can kill them. An estimated
twenty-five million dollars is spent annually on rabbit management by landowners,
and the government in an attempt to keep the numbers in check. The European
Rabbits negative impact on the environment proves costly towards primary
production. It was estimated that in 2004 the rabbits cost primary production
$113 million in production lost and control costs (4). However the introduction of RHD into
the populations has provided some benefits, and has increased production of
meat and wool. It is difficult to
put a monetary value on how much the rabbit has cost the Australian government
so far in economic loss as well as the loss of valuable species of plants and
animals and land destruction.
The Australian
government is aiming to eventually become “Rabbit-Free”. An event that is
difficult to picture given the still large population numbers. In order for a
Rabbit-Free Australia to be possible, population control methods are going to
have to be increased and ways found to make them more effective. Biological
methods do not seem to prove to be an effective long-term solution, especially
since the rabbit populations have developed resistance to both viruses that
have been introduced in hopes of wiping out the species. New and different
viruses would have to keep being introduced and this could have disastrous results.
Once introduced, the spread of disease cannot be controlled. The biggest
problem is that the European Rabbit populations have been shown to bounce back
quickly from distress without significant damage. Even in declining populations
control methods cannot be relaxed as the numbers could easily begin to increase
again. Eradication measures, in order to be effective, need to be organized and
persistent. All in all, a Rabbit-Free Australia does not seem likely.
Works Cited
(1)
Cooke, B. D., and F. Fenner. "Rabbit Haemorrhagic Disease and the
Biological Control of Wild Rabbits, Oryctolagus Cuniculus, in Australia and New
Zealand." Wildlife Research 29.6
(2002): 689-706.CSIRO PUBLISHING -
Wildlife Research. Web. 28 May 2013.
(2)
"Department of Primary Industries." Rabbits
and Their Impact. N.p., June 1999. Web. 29 May 2013.
(3)
"RISK ASSESSMENT FOR AUSTRALIA – European Rabbit." Invasive Species Specialist Group.
Government of Western Australia Department of Food and Agriculture, 27 Aug.
2008. Web. 27 May 2013.
(4)
"Why Are Rabbits a Problem?" Foundation
for Rabbit-Free Australia Inc. N.p., n.d. Web. 27 May 2013.
(5)
Zukerman, Wendy. "Australia's Battle with the Bunny." ABC Science.
N.p., 8 Apr. 2009. Web. 27 May 2013.
No comments:
Post a Comment