How Many People Can Live on Planet Earth?
The world population is the total number of living humans on the planet Earth, currently estimated to be 6.94 billion by the United States Census Bureau as of July 1, 2011.
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.
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."
The world’s population has significantly increased in the last 50 years, mainly due to medical advancements and substantial increases in agricultural productivity.
The world population has experienced continuous growth since the end of the Bubonic Plague, Great Famine and Hundred Years Wars in 1350, when it was about 300 million.
The highest rates of growth—increases above 1.8% per year—were seen briefly during the 1950s, for a longer period during the 1960s and 1970s; the growth rate peaked at 2.2% in 1963, and declined to 1.1% by 2009.
Annual births have reduced to 140 million since their peak at 173 million in the late 1990s, and are expected to remain constant, while deaths number 57 million per year and are expected to increase to 80 million per year by 2040.
Current projections show a continued increase of population (but a steady decline in the population growth rate) with the population to reach between 7.5 and 10.5 billion by the year 2050.
Asia accounts for over 60% of the world population with more than 4 billion people. China and India together have about 37 percent of the world's population.
Africa follows with 1 billion people, 15% of the world's population. Europe's 733 million people make up 11% of the world's population. Latin America and the Caribbean region is home to 589 million (9%), Northern America is to 352 million (5%) and Oceania to 35 million (0.5 %).
It is estimated that the population of the world reached one billion in 1804, two billion in 1927, three billion in 1960, four billion in 1974, five billion in 1987, and six billion in 1999.
It is projected to reach seven billion in October 2011, and around eight billion by 2025–2030.
By 2045–2050, the world's population is currently projected to reach around nine billion, with alternative scenarios ranging from 7.4 billion to 10.6 billion.
Projected figures vary depending on such things as the underlying assumptions and which variables are manipulated in projection calculations, especially the fertility variable.
Such variations give long-range predictions to 2150, ranging from population decline to 3.2 billion in the 'low scenario', to high scenarios of 24.8 billion, or soaring to 256 billion assuming fertility remains at 1995 levels. There is no estimation on the exact day or month the world's population surpassed both the one and two billion marks.
The day of three and four billion were not officially noted, but the International Database of the United States Census Bureau places them in July 1959 and April 1974. The United Nations did determine, and celebrate, the "Day of 5 Billion" (July 11, 1987), and the "Day of 6 Billion" (October 12, 1999).
The International Programs division of the United States Census Bureau estimated that the world reached six billion on April 21, 1999 (several months earlier than the official United Nations day).
The "Day of 7 Billion" has been targeted by the United States Census Bureau to be in March 2012, while the Population Division of the United Nations suggests October 31, 2011.
The scientific consensus is that the current population expansion and accompanying increase in usage of resources is linked to threats to the ecosystem.
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.
At the time, the world population stood at 5.5 billion, and lower-bound scenarios predicted a peak of 7.8 billion by 2050, a number that current estimates show will be reached around 2030.