1. Water supply. Water is one of the basic elements of live, and it is needed to preserve the balance of every ecosystem. It cools down and cleanses the environment and is used by plants and animals to carry out vital functions. As human population increases, so does the consumption of water. In the past fifty years, the per capita availability of fresh water has decreased by one third.* Fresh water supply is a problem in most of the developing countries, especially those located in arid climates such as in Africa, South America and Asia. In some African countries, fresh water needs to be carried daily from sources more than two hours walking distance. Water supply is an issue in urban areas as well. In Beijing, the water table falls down with as much as two meters annually.*
2. Water pollution. The problem with water is not only overconsumption, but also pollution. "More than 95% of urban sewage in developing countries is discharged untreated into the nearest waterway or field."* The main contributors to water pollution are factories and open mines, discarding waste water with heavy metals, toxic substances and solid waste, which are virtually impossible to purify. The situation is even worse when it comes to ocean exploitation and pollution. Overfishing changes the balance in coastal ecosystems and decreases fish populations. Sometimes it might even lead to extinction of certain marine species. Overfishing also damages coral reefs, because it allows algae to overgrow them. It turns out that the ocean is "the ultimate garbage dump "* because eventually all of the sewage, sediment from forest clearing, fertilizer and pesticide run-off flow into it. It is important to preserve the ocean, not only because it is an important source of food, but also because it plays a major role in climate regulation. The circulation of cold and warm water protects the earth from extreme temperature fluctuations. In addition, oceans absorbs between 30 and 40% of the CO2 given off as a result of human activity, thus keeping global warming at stake.
3. Soil Degradation. Population growth results increases the demand for food production. Since the arable land in many of the overpopulated regions is limited, farmers begin to cultivate dry, hilly, nutrient-poor areas that are not very suitable for farming. Exploiting such lands makes them easily susceptible to erosion and loss of nutrients. For example, in search for farmland in Indonesia, peasants have been planting their crops on steep slopes. As a result, almost one half of Java's land is now in danger of erosion.* Globally, the statistics are even more frightening. It is estimated that 1.2 billion hectares of land, approximately the size of Europe, U.S. and Mexico combined, have lost much of their agricultural output capability in the last 50 years.*
4.Deforestation. The search for more farmland causes other damaging agricultural practices such as slash-and-burn cultivation. Basically, a forest area is burned and converted into pasture, but due to poor soils, it looses its productivity in about three years.* This initiates a vicious circle which results in the deforestation of large areas, mostly in tropical regions. Deforestation is also caused by the use of wood as fuel, since 9 out of 10 African households use wood for cooking and heating. This is the reason why Ghana lost almost a third of its dense forest from 1938 to 1980.* In addition, the building of roads and the expansion of residential areas have contributed to the loss of primary forest.
5. Loss of biodiversity. All of the previously described effects of overpopulation on the environment lead to the destruction of the natural habitat of many wildlife species. The natural flora and fauna have been under constant pressure to adapt to a quickly changing environment. Since they have been unable to do so, they have been displaced from their natural ecological niche. The constant clearing of the Amazon forest has had devastating effect on many rare tropical species. It has been estimated that 10% of the species in the region have become extinct.*
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