Abstract
Some pests and weeds are considered by the Australian government to be of national significance. Most of these species were introduced from other countries and continents. Red fox (Vulpes vulpes) and the Alligator Weed (Alternanthera Philoxeroides) are some of the invasive species which threaten the ecology and several sectors of the Australian economy.
This document discusses why and how these species were introduced in Australia, factors which ensured their successful establishment in the country, as well as, their ecological and economic impacts. Finally, it examines the advantages and disadvantages of the control methods used to manage them.
Introduction
Numerous invasive species have been introduced in Australia over the years. These species are considered pests and have become a serious threat to biodiversity as well as agriculture in the country. Generally, pests have a direct effect on the environment/ecosystem as well as on human life wherever they exist.
Their rate of reproduction is high making it difficult to control them. Most of them were introduced either deliberately or by accident, including some brought in to assist with the control of other nuisance species.
Among the animal pests in Australia is red fox (Vulpes vulpes) also known as the European red fox was introduced in Australia in 1855 from Europe (Department of Sustainability, Environment, Water and Communities 2010).
Since its introduction in Australia, it has spread across most parts of the country, although it is no longer found in the tropical north as well as some off-shore islands (Tasmanian Department of Primary industries, Parks, Water and Environment, 2010). Vulpes vulpes is classified as a serious invader to native animals as it kills them.
On the other hand, one of the weed species which has invaded the ecological system of Australia is the Alligator Weed (Alternanthera Philoxeroides). It was also introduced from Parana River region, South America (Everitt, Little & Lonard, 2007, 55).
They have spread in Queensland, Victoria, Western Australia, New South Wales, Northern Territory, Tasmania and South Australia. According to Bonila and Gunasekera (2001, 17) Alternanthera Philoxeroides is among the top 20 weeds posing serious threats and therefore causes significant concern in Australia.
How and why the species were introduced in Australia
According to Cuthbertson and Parsons (1992, 155) Alternanthera Philoxeroides was first introduced in Newcastle, New South Wales from South America and has since spread to all states in Australia. It has viable seed which aids its dispersal. As a result it spread from South America through pieces of mud which it used to attach itself to ships which sailed from South America.
It was first introduced in this region during in 1946 when ship ballast was abandoned near New Castle (Cuthbertson and Parsons 1992, 155). According to the Rural Industries Research and Development Corporation (2011) Alternanthera Philoxeroides was introduced to Newcastle, New South Wales as a culinary herb.
Red fox which has also greatly contributed to serious breakdown of Australian ecology was first introduced in the country from 1855 (Cowan & Tyndale-Biscoe 1997, 31).
They were first released in Melbourne, Victoria. They were deliberately introduced to the country for recreational hunting. European red fox was hunted by humans beginning 1865. Hunting had started back in 1839 in Australia as people sought after kangaroos, rabbits and dingoes.
Factors which contributed to their successful establishment
The weed has the ability to survive in terrestrial, Aquatic as well as semi-aquatic habitats in temperate, tropical plus in sub-tropical regions. All the regions in Australia where the weed has spread all have the characteristics of these climatic regions. The existence of rivers, wetlands and river tributaries provided the optimum condition for their survival.
Red fox can survive in various habitats which include alpine, urban, as well as, arid areas (Pearson & Pyres 1998, 87). It can also live in lightly wooded regions, and grasslands. Australia has wooded areas which are found in the country’s agricultural landscapes. This offers a wide range of food and shelter for the fox. The fox can also survive in a cleared farming land which has some livestock such as lambs which it can prey on.
Besides, the fox can eat almost anything including small animals, insects and fruit (Larivière & Pasitschniak-Arts 1996, 6). In each environment, red fox is at the apex of the food chain. This enables it to survive even when its preferred prey, small animals, is less available during the summer seasons.
Australia has all types climates which the fox can survive in, and due to this, red fox has established itself firmly across the country. On the contrary, native animals of Australia have not yet evolved to protect themselves against the fox because of the circumstances in which red fox was introduced.
The fox was introduced so suddenly that the native animals were killed to feed the young foxes. This helped sustain the population of the red fox, which has since become the head of the food chain.
Ecological effects
Red foxes have had several long-term effects on the Australian environment. One major effect is the decline of biodiversity. Predation by red fox has contributed significantly to the decline of native species in the country and still continues to undermine the efforts of the Australian community to conserve the threatened species which includes the night parrot, malleefowl, as well as, the bridled nail-tail wallaby.
The fox has greatly contributed to the reduction in populations of ground-nesting birds, reptiles like the green turtle, as well as, small-to-medium sized mammals like the greater bilby. The fox often loots loggerhead turtle nets. Furthermore, it eats eggs in nests found on the beach. Loggerhead turtles are protected at Mon Repos Conservation Park in Queensland since they are endangered.
If these foxes are allowed to continue to breeding, as well as remain among the wild animals for much longer period, the fragile ecology of Australia will be destroyed. This means that it will be difficult to recover this unique environment. In addition, they are carriers of rabies.
The spread of rabies could destroy the fragile Australian ecosystem. The disease affects both human beings and animals. Thus eradicating it would be very difficult.
Red foxes normally eat berries in summer seasons when their favourable food resources are not available. In addition, the fox competes alongside native predators which include eagles. In the past, the fox has competed against Tasmania Devils which were once abundant across the mainland; however, it is now found in Tasmania only. Others included Tasmania Tiger, Thylacine, and Tasmania Wolf which are now extinct in the country.
Even though the red fox endangers the existence of many native animals, it is itself endangered by some animals. These animals include the Western Quoll, Red-Tailed Phascogale, Numbat, as well as, Brush-Tailed Bettong which are majorly found in South-Western Australia.
These animals are poisonous to the red fox since they eat Gastrolobium, as well as, Oxylobium plants, which are poisonous to animals especially the red fox (Cowan & Tyndale-Biscoe 1997, 31).
These plant species have flouroacetate which is the chemical used to make the poison baits used in 1080 (Cowan & Tyndale-Biscoe 1997, 31). On the contrary, these animals considered to be dangerous to the fox have developed immunity to the chemical, and therefore they store the poison in their flesh. When the red fox eats the animal, it dies.
Alligator weed disrupts the aquatic environment by covering the surface and therefore hindering penetration of light into the water or soil (Groves, Richardson & Shepard 1995, 07). This adversely distresses aquatic fauna as well as flora. Economic impacts
Economic Impacts
Alligator weed has impacts on several sectors of the economy. The plant has increased the would-be costs to irrigation farming (Groves, Richardson & Shepard 1995, 10). It is expected that should the alligator weed not be controlled, then, the Barren Box Swamp infestation will cost about $250 million annually (Department of Sustainability, Environment, Water and Communities 2010).
It is also threatening the sustainability of the turf industry in the Sydney Basin. The vegetable industry in the Hawkesbury-Nepan region is also threatened; the industry is estimated to be worth $150 million a year (Department of Sustainability, Environment, Water and Communities 2010).
Other than the vegetable industry, there is the extraction industry in the same region, which also under threat. Should these resources be contaminated with the alligator weed, then the resources will have to be restricted. Moreover, it also threatens soy bean as well as sugar cane industries in the Richmond region (Groves, Richardson & Shepard 1995, 11).
Alligator weed also interferes with livestock farming. The plant contaminates grazing pastures and causes cancerous lesions in cattle. At some point, they become so dense that they deny livestock access to drinking water. This also implies that it limits access to, as well as, use of water. It can also block and damage pumps.
In Warragamba Dam in Sydney, the weed causes sedimentation and therefore its major water supply, as well as, storage system (Department of Sustainability, Environment, Water and Communities 2010). It obstructs stream flow of water and as a result leads to sedimentation. This contributes to flooding of the region, and structural damage to infrastructure.
Red foxes have significant impacts on the Australian economy. It threatens the existence of native species as well as ecological communities. This impacts on the national heritage as it reduces species population (wildlife resources) in the country.
The night parrot, malleefowl, as well as, the bridled nail-tail wallaby are some of the species which have been identified as threatened by red fox (Department of Sustainability, Environment, Water and Communities 2010).
Red fox also causes losses to farmers especially those who keep livestock. The fox preys on the kid goats, poultry, as well as, newborn lambs. Moreover, they can also pass rabies on to livestock as well as native mammals. This costs the Australia economy millions of dollars per year since they kill livestock as well as by being a pest to farmers.
Advantages of the methods used to control red fox
Among the methods the government and the Australian community has employed is the prevention of the spread of red foxes to new regions which includes islands.
Protection of the islands has been major priority in controlling red fox population. Islands have often been used as refugee habitats for species which are not available on the mainland any more. This has been effective in eradicating red fox from high-conservation-value islands.
Adoption of poison baits on fences has also been successful in reducing the population of red foxes. This has been applied in south-west Western Australia and Eastern Australia. It has enabled native mammals to start to recover, and as a result, return to their former habitats.
This method has also reduced the pressure on native species threatened by the red fox. It helps promote the maintenance, as well as, recovery of native animals together with the ecological communities which have been affected by red fox predation.
Demerits of the methods used to control red fox
Although the Australian community has adopted payment of bounties to encourage people to remove red foxes from among the wild animals, reduction of damages from the fox has not been effective (Tasmanian Department of Primary industries, Parks, Water and Environment, 2010). Again, hunting has not been able to achieve significant or long-term impact red fox population as well as the damage they cause.
The application of poison baits in controlling red fox could have effects on other animals which are the target for elimination. Poison baits may also have similar effects on other animals, and therefore lead to their decline in areas where they are used. Besides, poison baits are very expensive and requires much resources to maintain them indefinitely. In south-west Western Australia, a large scale 1080-poison baits is used to control red fox.
Advantages of the methods used to control alligator weed
There are several methods which have been applied in Australia to control alligator weed. These control methods include physical, chemical and biological controls, and through legislation.
Physical control method which involves the manual digging and burying of the alligator weed after having applied herbicides which kills any above-underground plant growth. This ensures immediate eradication of the alligator plant (NSW Department of Primary Industries 2008). It has successfully reduced floating mats which grow in Georges River as well as parts of Hawkesbury-Nepean region.
Disadvantages of the methods used to control alligator weed
One of the methods which have been applied in managing alligator weed is the adoption of alternative vegetable as part of the eradication program.
The most notable alternative vegetable that has been adopted is the lesser joy weed which is scientifically known as Alternanthera denticulata (Bonila and Gunasekera 2001, 19). However, this does not help eliminate alligator weed as most of it grows wildly. Wetlands and river habitat where the weed grows is not affected by this program.
Chemical control method applied in Australia is not effective as it takes long to eradicate the weed. Alligator weed can tolerate most herbicides. This means that application of these herbicides may only suppress the weed. Consequently, this method may take as a long as 6 years to completely eradicate the weed since in some cases, the herbicides are applied annually.
Again, since the alligator weed is tolerant to most of these herbicides (NSW Department of Primary Industries 2008), it implies that large quantities are used in process.
This can be dangerous to other plant species and could lead to their death. This means that chemical control method may lead to further loss of biodiversity. Application of chemicals could also lead to the death of soil micro-organisms which play key role in breaking and enriching the soil.
Physical control on the other hand, cannot be adopted in large and extensive alligator coverage areas. It is difficult to carry out deep manual digging for burying the weed that covers a wide area. Besides, applying herbicides to prevent above-underground plant growth could affect many plant and animal species which were not intended.
Conclusion
Red fox and alligator weed are among the invasive species which are of great significance to Australia. Both of them cause great damage to the environment, which in turn affects the country’s economy. If they are not carefully controlled, then they may cause reduction of population of various species and even lead to their extinction.
Thus, it is important to devise better and more environmentally friendly ways of managing them and their impacts. This means that more research has to be done to enable the Australian community understand their impacts and develop more advanced ways of controlling their population and impacts on the ecology, other species and human life.
It is also important to understand that these species also play vital roles in the ecosystem, and therefore the control measures adopted should not aim at eliminating them, but also protecting them. Finally, the local community should be involved in controlling these pests and weeds in order to achieve sustainable environmental management.
Reference List
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