What Causes Populations to Grow?
It took the human race thousands of years to reach a population of 1 billion, but during the last 200 years, population has exploded. According to the United Nations, the world population was nearing 7 billion in 2011 and is projected to reach 10.1 billion in the next 90 years. Population growth occurs for a number of reasons, but many boil down to the fact death rates have fallen while birth rates have increased.-
Fertility Rates
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Population growth occurs when the average woman has about 2.1 children over her lifetime. If fertility rates remain lower than that for more than a generation, a country's population will level off or decrease. The U.N. also measures fertility rates by the number of women who have a daughter surviving "to the age of procreation." Higher fertility countries are mainly in Africa, but some are also in Asia, Oceania and Central America. Bolivia in South America is also on that list. Countries with lower fertility rates are in Europe, Asia and Western Hemisphere countries like Canada, Brazil and Chile. Other factors can combine with fertility rates to cause populations to grow faster.
Life Expectancy
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One factor is people are simply living longer. Between 2005-10, life expectancy was 68 years worldwide. The U.N. projects the age will rise to 81 by 2100. The factors for longer life are varied, but overall death rates fell faster than birth rates.
Health Care Advances
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In the last 200 years, advances of antibiotics, vaccines and overall public health helped cut the death rate from common diseases such as influenza, smallpox and polio. Scientists have also made breakthroughs in previously incurable diseases, such as HIV, to improve survivability.
Better Food Production
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As the world's population has grown, advances in agriculture have improved food production to meet the demand. Those advances include new kinds of seeds, better technology in farm equipment, and new kinds of fertilizers and pesticides.
Better Public Health
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In the 1800s, scientists became more aware that what goes on in an community can have an effect on a person's health. Contaminated public water supplies, for example, increased the outbreak and spread of diseases like cholera. Better waste treatment has improved the quality of drinking water.
The Developing World
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But not all countries have benefitted from these advances. In portions of Africa, the AIDS epidemic has led to a lower life expectancy. In portions of Asia and Latin America, wastewater treatment is not as prevalent and has led to more disease. But even in these regions, life expectancy is expected to increase over the next century.
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