Deforestation
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When trees are cut down in large amounts, the ecosystem losses its biodiversity, had major climate changes, a decrease in soil fertility and an increase in soil salinity. Biodiversity is the variety of life in the world or in a particular habitat or ecosystem. In Australia because of deforestation there has been a major decrease in animals. First many bird species has been lost in Victoria, Queensland, New South Wales, Western Australia and the Mount Lofty Ranges in South Australia. There has also been a big decline in reptiles and native plants, which has been overcome by the sudden growth of weeds. Climate change also plays a big part, it increases temperatures and reduces rainfall. Also cutting down trees changes or breaks the natural water cycle. The natural water cycle is when the trees maintain soil moisture and release water vapor back into the atmosphere. This can cause a decrease in many sources and animals which is bad for the country as a whole and decrease the amount it can actually decrease. In the long run if this continues, Australia's GDP would decrease.
Agriculture clearing and overgrazing
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Because of clearing out land for agriculture, already 13% of Australia's original land has been removed since European settlement. Agriculture clearing is one of the biggest environmental issues in Australia since it's in one of the top 10 to have cleared the most land in the past 5 years. About 90% of native vegetation in the eastern temperate zone has been removed for agriculture, industry, transport and human habitation and about 50% of Australia's rainforests have been cleared and the part of Australia covered by forest or woodland has been decreased by more than one third. Because of the damage that has been cause around 5% of Australia's higher plants, 7% of reptiles, 9% of birds, 9% of freshwater fish, 16% of amphibians and 23% of mammals are listed as extinct, endangered or vulnerable. Overgrazing is when the grassland is so heavy that the vegetation is damaged and that the ground is more vulnerable to erosion which is the cause of invasive plants. Now in Australia less than 2% grasslands remain. This is connected to economics because it shows how the market's demand for certain products increased causing the farmers to clear out more land and ruin the soil for the consumers.
Overfishing and illegal fishing
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Overfishing and illegal fishing is a major problem in Australia. Overfishing has already sadly decreased Australia's fish stock levels dangerously low. The two main causes or reasons for this is because some areas already have a low biological productivity and another is the intensive fishing and commercial and recreational fisheries. Statistics show that in 2005, 17 out of the 82 species in Australian waters were considered as overfished. Some of those species are the southern blue tuna, blue warehou, silver trevally, orange roughy and the bigeye tuna in the Pacific and Indian Oceans. Illegal fishing also puts an enormous amount of certain species because the demand for the certain body parts of them are very high. This is connected to economics because it's showing how the certain species of fish are becoming more scarce and soon there will be a higher demand for them.
Introduction of exotic species
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Every year in Australia, there is an estimate that they gain about 20 new pests or diseases. Some of the examples are cane toads, rabbits, willows and the more recent ones would be black striped mussels and red fire ants. Common animals like feral cats, foxes and rabbits are usually the reason for local extinction and a decrease in range for the native species. But it's not just animals, weeds are also big problem. Weeds have more than 2500 species now thriving in Australia, they so far have invaded almost every landscape including bushland, rangeland, coast's, rainforests, deserts, and farms. Another reason for the introduction of new species is the Ballast waters, which ships 250 to 500 different species into the Australian waters. This is connected to economics because of the sudden increase of different species, causing the olders ones to get older.
Pollution
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Pollution is mostly caused by the intensive agriculture, which is affecting the coasts and oceans. Statistics estimate that about 19,000 tonnes of phosphorous and 141,000 tonnes of nitrogen are in rivers flowing to the coast.