Soil Erosion

“The increase in human population to a present day level of over six billion is having an impact on the biosphere that is greater than ever before”. The vast amount of impact is greatly due to three major activities including agriculture, industrialization, and urbanisation.

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Agriculture being one of the major activities contributing to the impact on the biosphere, is the clearing of natural habitat, which most of our ancestors did when they settled in Australia, and consequently without the knowledge of the side effects of clearing forests, cultivating the soil, repeatedly harvesting crops, as well as today’s humans who still continue, can lead to dryland salinity and soil erosion, which both accordingly lead to land degradation. Although the seriousness of the agriculture is getting worse, it can be combated.

Humans have been obliterating forests all over the world for reasons like, timber, firewood, settlement and agricultural purposes. The benefit for agriculture is almost pointless because the soil in tropical rainforests is of poor nutrients, although the land often becomes productive after a couple of years after the clearing but when there is a limited supply of nutrients in the soil, which is rapidly used up, the crop just declines. Accordingly the farmers leave the land and move onto some where more productive.

As a result of this the top soil either washes away or blows away with the wind because there is no plant roots to hold it in place. The impact that agriculture has on the biosphere is a problem in Australia and has been present for over 150 years. Approximately 50% of native eucalypt forest and 75% of rainforests have been cleared, primarily for agriculture purposes and today that land is unproductive, although the land is infested with introduced weeds and/or the land is suffering from land degradation.

In some farming areas of Victoria there is poor regeneration of Red Gum trees because any of the new growth is grazed by sheep. Trees on farmlands can not regenerate if grazing of the new growth continues, and consequently the old trees will die and so will some of the native animals who vegetate and their food source is these trees. Dryland salinity occurs when native vegetation is cleared. As a result of this the exclusion of water by deep-rooted shrubs and trees is decreased, and the level of groundwater rises, which makes the dissolved salts rise closer to the surface.

Once the salty water reaches a depth of roughly 1. 5-3m it rises to the surface by passageways. Dryland salinity is particularly evident in areas of South Australia and is at a bad situation in Western Australia. One thing that decreases the amount of dryland salinity is planting native saltbush which can be grown because of its tolerance of salt. It lowers the water level and provides food for native animals and also protects the soil against soil erosion which is also a crisis through out Australia.

Since European settlement in Australia, the state of the soil has been significantly altered due to agriculture purposes such as vegetation clearance, grazing, cultivation, the introduction of introduced soil flora and fauna and the use of fertilisers, herbicides and pesticides. These practices accounts for soil erosion. Soil erosion is one of the most significant problems that have resulted from agricultural purposes. Soil erosion permanently reduces the productivity of agricultural lands.

Soil erosion occurs after forests are cleared and accordingly the top soil either washes away or blows away with the wind because there is no plant roots to hold it in place. “There are about 10. 2 million hectares of agricultural land in South Australia and approximately 2. 43 million hectares (23. 8%) of this have a moderate to high risk rating of soil erosion, most of this is on Eyre Peninsula, the Murraylands and the South East”. The speed at which soil loss occurs is much better today than they were 10 years ago.

This is largely because of the change in agricultural practices in some areas. Although, when there are severe weather conditions, various areas are still affected by soil erosion. At the rate that soil erosion is happening, in 30-50 years time the top soil will not be present. Both Dryland salinity and soil erosion lead to land degradation. Land degradation is the decrease in the state of the land due to misuse and/or overuse, usually from a chain of events starting from loss of vegetation and other causes.

These include, grazing too many livestock (cattle/sheep) than the land can cope with, four wheel off road driving, the introduced European rabbit, which graze the vegetation right down to the top soil, and eat the seedlings, preventing any regenerate taking place. This is the same situation with other introduced species like, goats, camels, and other livestock, the overuse of fertilisers and pesticides which also make the soil less productive and even poison the soil.

Land degradation also affects the economical development of countries around the world. Land degradation not only affects the soils lushness but can also have a significant affect on water courses, including rivers, wetlands and lakes, therefore has potentially unfortunate impacts on lakes and reservoirs that are made for preventing bad flooding, supply irrigation, and produce hydroelectricity.

Although some might say that the affect that agriculture has on the ecosystem is permanently damaged, others say that it can be combated over a long period of time and a lot of support from everyone concerned. The best thing possible that us as Australians can do to reduce the fact that we have one of the worst land degradation problems on Earth is “to plant billions of trees over the next 20 years”, because 40% of Australia’s degraded land is in need of revegetation.

Regreening programs across Australia and possibly overseas have under gone revegetation practices to help this problem. Not only will this reduce soil erosion and dryland salinity problems but also because of the large amount of planting taking place, it also increases the efficiency on farms, by supplying shelter and food for livestock and in addition increases the bird populations, which feed on insect pests. The activities of each individual person may appear to be insignificant, but added up they are contributing to a global impact of a great magnitude”. Every individual has to take some concern towards the environment, otherwise the severe problems that are already at a point where some things are permanently damaged, will affect us more greatly in the future if action doesn’t take place now.

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