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Biology Assignment

Environment density variescarrying capacity代寫

Location
The appropriate kangaroo density varies in different area or type of ecosystem because of different carrying capacity and management objectives. And different areas or types of ecosystem are discussed as follows.
1. Public Land
Public land was defined as any of the following purposes: a wilderness area; a national park; a nature reserve; a special purpose reserve; an urban open space; a cemetery or burial ground; the protection of water supply; a lake; a sport and recreation reserve; a heritage area (ACT 2007). Lowland grassy woodland and native grassland, grasslands in the western and southern ACT and Googong dam area are the main types of public land.
1.1 Lowland Grassy Woodland and Native Grassland
Eastern grey kangaroo plays an important role in the ecosystem of the native grassland. For example, kangaroo helps defoliation, which is essential to keep ecology in balance. However, in some areas kangaroo population has reached ecological carrying capacity; in others population is still increasing. The high density of kangaroo leads to overgrazing, decreasing the grassland communities and animals and plants depending on these grassland. Threatened species is being lost with the increasing of kangaroos. Preventing degradation of these areas, the management of kangaroos is required. So, for lowland grassy woodland and native grassland, the population of kangaroo should be controlled at densities that conserve the balanced ecosystems. The management approaches have been applied in some area, but some native grassy ecosystems are managed by the Commonwealth Government, where co-ordination arrangements about responsibility of the management will be undertaken.
1.2 Grasslands in the Western and Southern ACT
These lands mainly include Namadgi National Park, the Tidbinbilla precinct and the Lower Cotter Catchment. In Namadgi National Park, kangaroo populations seem stable and high with restriction of food supply and predators. In Tidbinbilla Precinct, for it’s an ideal place for kangaroo to habit, the eastern grey kangaroo dominates the grassy valley areas. This results in overgrazing and other environmental problems. However, as a wildlife enclosure, seeing kangaroos is welcomed by tourists. In Lower Cotter Catchment, it lacks related data on kangaroo populations. So there are a few differences in the management strategies among these areas. It seems that there is no need to do anything in Namadgi National Park; in Tidbinbilla, it’s hard to decide whether the population should be managed now unless undesirable impacts appear; in Lower Cotter Catchment, more data are needed.
1.3 Googong Dam Area
Googong Foreshores supply raw water for potable water supply, owns natural and cultural heritage and provided recreational opportunities. They are also ideal place for kangaroos to live. Kangaroo populations damage herbage and influence the water supply. Management of kangaroo grazing will be undertaken.
2. Non-public Land
These lands include roadsides, horse paddocks and leased territory land managed by individual or institutional land holders. No kangaroo management issues to roadsides have been reported. But horse paddocks were threatened by kangaroos and grazing pressure from kangaroos decreased the number of horses in government paddocks, where fencing is carried out. In the rural areas, they have impacts on the rural production to some extent, but not heavily, because rural kangaroo culling program allow rural lessees to cull kangaroos with license.
3. Conclusion
In many native grass land areas, the populations of kangaroos are managed because their damage to the ecosystems. But considering the area under the Commonwealth Government, negotiations are undertaken to manage the kangaroos. In grasslands in the western and southern ACT, the damage of kangaroos is less serious. The management should be taken unless undesirable matter occurs. In Googoog dam area, the density has been controlled to protect water supply and ecosystems. In non-public land, just culling and fencing may help the management of kangaroos.
Impacts
1. Environment
The grassy ecosystems contain a variety of plants and animals, but they are reduced to fragments and are subject to ongoing threats, one of which is the kangaroo. Some plant and animal species became threatened. The control of kangaroo populations helps the ecosystems to some extent, because too high density of kangaroo has damaged the ecosystems.
However, the management may hurt the Eastern Grey Kangaroos. Culling may change the genetic structure and genetic diversity of a population. Concerns have also been expressed over the impact of culling on the maintenance of genetic diversity and fitness, particularly by the selective removal of big males. Fertilizing control can successfully reduce the reproduction in female Eastern Grey Kangaroos but there come with behavioral side effects to females. From the research, males prefer groups with more untreated females, which suggest that the fertilization treatment may result in higher male mobility. This may increase the risk of collisions with vehicles when the population of kangaroos targeted for contraception inhabits areas close to roads supporting heavy traffic. This side effect should be weighed against a likely decrease in the probability of road accidents due to lower population growth resulting from contraception treatment.
2. Economics
Decreasing kangaroos helps the economics because they influence the agriculture and livestock. Clearing of land for cropping and pasture development, fencing and the introduction of livestock has influenced more than 95% of Australia’s vegetation. Generally, areas protected from over-grazing by kangaroo contain greater species diversity and vegetative biomass. Furthermore, where destocking is desired for rehabilitation purposes, kangaroos may negate any benefits from removing livestock, if kangaroo numbers are too high.
On the other hand, carrying out the management strategies took a large amount of money. Culling by shooting is most cost-effective method but it still needs substantial regular cost, let alone fertility control and environment modification. At the same time, the kangaroo is an important component of nature-based tourism in ACT, so the tourism incoming impaired by the management to some extent.
3. Social Considerations
It was reported that kangaroos attacked people including genuine attacks and defensive behavior. Attacks usually happened in the places where human activities impinge on kangaroo habitat. No matter how and where attacks occurred, management of kangaroos decreased the possibility of attacks. On the meantime, incidence of vehicle-kangaroo collisions will be reduced.
However, ‘animal rights’ campaigns are against management action. Some organizations promoted that kangaroos are on the brink of extinction, which was denied by research result of 240 mammalogists. These philosophical differences always exist, and may never be resolved.
4. Conclusion
The advantages and disadvantages of kangaroo management both exist. Only the management strategies are carried out properly, the advantages will overwhelmed the disadvantages.
 
Reference
Act Government, 2007, “Planning and Development Act 2007”, retrieved 12/04/2013, < http://www.legislation.act.gov.au/a/2007-24/20070927-33748/pdf/2007-24.pdf >.
Act Government, 2010, “ACT Kangaroo Management Plan”, retrieved 12/04/2013, < http://www.tams.act.gov.au/__data/assets/pdf_file/0012/394698/Kangaroo_Management_Plan_complete_for_web.pdf >
 

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