Overpopulation is a 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] Steve Jones, head of the biology department at University College London, has said, "Humans are 10,000 times more common than we should be, according to the rules of the animal kingdom, and we have agriculture to thank for that. Without farming, the world population would probably have reached half a million by now."[2] The world’s population has significantly increased in the last 50 years, mainly due to medical advancements and substantial increases in agricultural productivity.
The recent rapid increase in human population over the past two centuries has raised concerns that humans are beginning to overpopulate the Earth, and that the planet may not be able to sustain present or larger numbers of inhabitants. The population has been growing continuously since the end of the Black Death, around the year 1400;[3] at the beginning of the 19th century, it had reached roughly 1,000,000,000 (1 billion). Increases in medical technology have led to rapid population growth on a worldwide level. Current projections show a steady decline in the population growth rate, with the population expected to reach between 8 and 10.5 billion between the year 2040[4][5] and 2050.[6] Map of countries by population density, per square kilometer.
(See List of countries by population density.) Areas of high population densities, calculated in 1994.Map of countries and territories by fertility rate (See List of countries and territories by fertility rate.) Human population growth rate in percent, with the variables of births, deaths, immigration, and emigration - 2006The scientific consensus is that the current population expansion and accompanying increase in usage of resources is linked to threats to the ecosystem.[citation needed] The InterAcademy Panel Statement on Population Growth, which was ratified by 58 member national academies in 1994, called the growth in human numbers "unprecedented", and stated that many environmental problems, such as rising levels of atmospheric carbon dioxide, global warming, and pollution, were aggravated by the population expansion.[7] At the time, the world population stood at 5.
5 billion, and low-bound scenarios predicted a peak of 7.8 billion by 2050, a number that current estimates show will be reached around 2022. DefinitionOverpopulation 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 the way resources are used and distributed throughout the population. Overpopulation can result from an increase in births, a decline in mortality rates due to medical advances, from an increase in immigration, or from an unsustainable biome and depletion of resources. It is possible for very sparsely populated areas to be overpopulated, as the area in question may have a meager or non-existent capability to sustain human life (e.
g. a desert).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 and waste disposal. Overpopulation places competitive stress on the basic life sustaining resources,[9] leading to a diminished quality of life.
[10] [edit] History of concernConcern about overpopulation is relatively recent in origin. 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 hardly increased, remaining under 250 million.[11]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. [edit] History of population growthMain article: World population Data from World Population.
A population pyramid based on the 2011 Libyan population.The human population has gone through a number of periods of growth since the dawn of civilization in the Holocene period, around 10,000 BC. The beginning of civilization coincides with the final receding of glacial ice following the end of the last glacial period.[citation needed] It is estimated that about 1,000,000 people, subsisting on hunting and foraging, inhabited the Earth in the period before the neolithic revolution, when human activity shifted away from hunter-gathering and towards very primitive farming.[citation needed]Around 8000 BCE, at the dawn of agriculture, the population of the world was approximately 5 million.
[12] The next several millennia saw minimal changes in the population, with a steady growth beginning in 1000 BCE, plateauing (or alternatively, peaking) in 1 BCE, at between 200 and 300 million people. The Plague of Justinian caused Europe's population to drop by around 50% between 541 and the 8th century.[13] Steady growth resumed in 800 CE.[14] This growth was disrupted by frequent plagues; most notably, the Black Death during the 14th century. The effects of the Black Death are thought to have reduced the world's population, then at an estimated 450 million, to between 350 and 375 million by 1400.[15] The population of Europe stood at over 70 million in 1340;[16] these levels did not return until 200 years later.
[17]On the other side of the globe, China's population at the founding of the Ming dynasty in 1368 stood close to 60 million, approaching 150 million by the end of the dynasty in 1644.[18][19]England's population reached an estimated 5.6 million in 1650, up from an estimated 2.6 million in 1500.
[20] New crops that had come to Asia and Europe from the Americas via the Spanish colonizers in the 16th century contributed to the population growth.[21][22]Since being introduced by Portuguese traders in the 16th century,[23] maize and manioc have replaced traditional African crops as the continent's most important staple food crops.[24]Alfred W. Crosby speculated that increased production of maize, manioc, and other American crops "..
.enabled the slave traders [who] drew many, perhaps most, of their cargoes from the rain forest areas, precisely those areas where American crops enabled heavier settlement than before."[25]The population of the Americas in 1500 may have been between 50 and 100 million.[26]Encounters between European explorers and populations in the rest of the world often introduced local epidemics of extraordinary virulence. Archaeological evidence indicates that the death of around 90% of the Native American population of the New World was caused by Old World diseases such as smallpox, measles, and influenza.[27]Over the centuries, the Europeans had developed high degrees of immunity to these diseases, while the indigenous peoples had no such immunity.
[28]After the effects of the plagues had subsided during the 17th century, shortly before the Industrial Revolution, the world population began to grow once again. In parts of Asia, like China, the population doubled from 60 to 150 million under the Ming dynasty[citation needed].After the start of the Industrial Revolution, during the 18th century, the rate of population growth began to increase. By the end of the century, the world's population was estimated at just under 1 billion.[29] At the turn of the 20th century, the world's population was roughly 1.
6 billion.[29] By 1940, this figure had increased to 2.3 billion[citation needed]. Dramatic growth beginning in 1950 (above 1.8% per year) coincided with greatly increased food production as a result of the industrialisation of agriculture brought about by the Green Revolution.
[30] The rate of growth peaked in 1964, at about 2.2% per year. The world population was at some point in 2010 estimated to be 6,909,900,000, with unreported variability.
