24-06-2013, 03:08 PM
Overpopulation
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INTRODUCTION
Overpopulation is a generally undesirable condition where an organism's numbers exceed the carrying capacity of its habitat. The term often refers to the relationship between the human population and its environment, the Earth,[1] or smaller geographical areas such as countries. Overpopulation can result from an increase in births, a decline in mortality rates, an increase in immigration, or an unsustainable biome and depletion of resources. It is possible for very sparsely populated areas to be overpopulated if the area has a meager or non-existent capability to sustain life (e.g. a desert).
The population has been growing continuously since the end of the Black Death, around the year 1400,[citation needed] although the most significant increase has been in the last 50 years, mainly due to medical advancements and increases in agricultural productivity. Although the rate of population growth has been declining since the 1980s, the United Nations has expressed concern on continued excessive population growth in sub-Saharan Africa.[2] As of January 20, 2013 the world human population is estimated to be 7.061 billion by the United States Census Bureau,[3] and over 7 billion by the United Nations.[4][5][6] Most estimates for the carrying capacity of the Earth are between 4 billion and 16 billion. Depending on which estimate is used, human overpopulation may or may not have already occurred. Nevertheless, the rapid recent increase in human population is causing some concern. The population is expected to reach between 8 and 10.5 billion between the year 2040[7][8] and 2050.[9] In May 2011, the United Nations increased the medium variant projections to 9.3 billion for 2050 and 10.1 billion for 2100.[10]
The recent rapid increase in human population over the past three centuries has raised concerns that the planet may not be able to sustain present or larger numbers of inhabitants. The InterAcademy Panel Statement on Population Growth has stated that many environmental problems, such as rising levels of atmospheric carbon dioxide, global warming, and pollution, are aggravated by the population expansion.[11] Other problems associated with overpopulation include the increased demand for resources such as fresh water and food, starvation and malnutrition, consumption of natural resources faster than the rate of regeneration (such as fossil fuels), and a deterioration in living conditions. However, some believe that waste and over-consumption, especially by wealthy nations, is putting more strain on the environment than overpopulation.[12]
History of concern
Concern about overpopulation is ancient. Tertullian was a resident of the city of Carthage in the second century CE, when the population of the world was about 190 million (only three to four percent of what it is today). He notably said: "What most frequently meets our view (and occasions complaint) is our teeming population. Our numbers are burdensome to the world, which can hardly support us... In very deed, pestilence, and famine, and wars, and earthquakes have to be regarded as a remedy for nations, as the means of pruning the luxuriance of the human race." Before that, Plato, Aristotle and others broached the topic as well.[13]
Throughout history, populations have grown slowly despite high birth rates, due to the population-reducing effects of war, plagues and high infant mortality. During the 750 years before the Industrial Revolution, the world's population increased very slowly, remaining under 250 million.[14]
By the beginning of the 19th century, the world population had grown to a billion individuals, and intellectuals such as Thomas Malthus and physiocratic economists predicted that mankind would outgrow its available resources, since a finite amount of land was incapable of supporting an endlessly increasing population. Mercantillists argued that a large population was a form of wealth, which made it possible to create bigger markets and armies.
Causes
The root causes for overpopulation are many, but have everything to do with human psychology and the cycle of entrenched poverty, as well as the rest of the world's reaction to it. Areas with greater burden of disease and warfare, contrary to popular belief, do not experience less population growth over the long term, but far more over a sustained period as poverty becomes further entrenched. This is because parents and siblings who have experienced calamitous conditions suffer from a kind of post traumatic stress syndrome about losing their family members and overcompensate by having "extra" babies. These extra babies and calamities fuel a vicious cycle and only in the small minority of cases does it cease. As this cycle is compounded over generations, calamities such as disaster or war take on a multiplier effect. For example, the AIDS crisis in Africa is said to have killed 30 million to date, yet during the last two decades money and initiatives to lower population growth by contraception have been sidelined in favor of combating HIV,[62] feeding the population explosion that we see in Africa today. In 1990, its population was roughly 600 million; today it is over 1,050 million, 150 million more than if the HIV/AIDS crisis had never occurred.[63]
Carrying capacity
There is wide variability both in the definition and in the proposed size of the Earth's carrying capacity, with estimates ranging from less than 1 to 1000 billion humans (1 trillion).[69] A 2001 UN report said that two-thirds of the estimates fall in the range of 4 billion to 16 billion (with unspecified standard errors), with a median of about 10 billion.[70] More recent estimates are much lower, particularly if resource depletion and increased world affluence are considered.[71][72]
In a study titled Food, Land, Population and the U.S. Economy, David Pimentel, professor of ecology and agriculture at Cornell University, and Mario Giampietro, senior researcher at the US National Research Institute on Food and Nutrition (INRAN), estimate the maximum U.S. population for a sustainable economy at 200 million. And in order to achieve a sustainable economy and avert disaster, the United States would have to reduce its population by at least one-third, and world population would have to be reduced by two-thirds.[73]
Some groups (for example, the World Wide Fund for Nature[74][75] and Global Footprint Network[76]) have stated that the carrying capacity for the human population has been exceeded as measured using the Ecological Footprint. In 2006, WWF's "Living Planet Report" stated that in order for all humans to live with the current consumption patterns of Europeans, we would be spending three times more than what the planet can renew.[77] Humanity as a whole was using, by 2006, 40 percent more than what Earth can regenerate.[78]
Effects of human overpopulation
Some problems associated with or exacerbated by human overpopulation are:
• Inadequate fresh water[82] for drinking as well as sewage treatment and effluent discharge. Some countries, like Saudi Arabia, use energy-expensive desalination to solve the problem of water shortages.[83][84]
• Depletion of natural resources, especially fossil fuels.[85]
Resources
Overpopulation does not depend only on the size or density of the population, but on the ratio of population to available sustainable resources. It also depends on how resources are managed and distributed throughout the population.
The resources to be considered when evaluating whether an ecological niche is overpopulated include clean water, clean air, food, shelter, warmth, and other resources necessary to sustain life. If the quality of human life is addressed, there may be additional resources considered, such as medical care, education, proper sewage treatment, waste disposal and energy supplies. Overpopulation places competitive stress on the basic life sustaining resources,[111] leading to a diminished quality of life.[110]
David Pimentel,[112] Professor Emeritus at Cornell University, has stated that "With the imbalance growing between population numbers and vital life sustaining resources, humans must actively conserve cropland, freshwater, energy, and biological resources. There is a need to develop renewable energy resources. Humans everywhere must understand that rapid population growth damages the Earth's resources and diminishes human well-being."
Fresh water
Fresh water supplies, on which agriculture depends, are running low worldwide.[128][129] This water crisis is only expected to worsen as the population increases.[130]
Potential problems with dependence on desalination are reviewed below, however, the majority of the world's freshwater supply is contained in the polar icecaps, and underground river systems accessible through springs and wells.
Fresh water can be obtained from salt water by desalination. For example, Malta derives two thirds of its freshwater by desalination. A number of nuclear powered desalination plants exist;[131][132] However, the high costs of desalination, especially for poor countries, make impractical the transport of large amounts of desalinated seawater to interiors of large countries.[133] The cost of desalinization varies; Israel is now desalinating water for a cost of 53 cents per cubic meter,[134] Singapore at 49 cents per cubic meter.[135] In the United States, the cost is 81 cents per cubic meter ($3.06 for 1,000 gallons).[136]