Демографические изменения - перенаселение
The surge in population is both a cause of the changed relationship and one of the clearest illustrations of how startling the change has been, especially when viewed in a historical context. From the emergence of modern humans 200,000 years ago until Julius Caesar's time, fewer than 250 million people walked on the face of the earth. When Christopher Columbus set sail for the New World 1,500 years later, there were approximately 500 million people on earth. By the time Thomas Jefferson wrote the Declaration of Independence in 1776, the number had doubled again, to I billion. By midway through this century, at the end of World War II, the number had risen to just above 2 billion people.
In Other words, from the beginning of humanity's appearance on earth to 1945, it took more than ten thousand generations to reach a world population of 2 billion people. Now, in the course of one human lifetime - mine - the world population will increase from 2 to more than 9 billion, and it is already more than halfway there.
Overpopulation is often defined as the condition of having more people than can live on Earth in comfort, happiness, and health and still leave the planet a fit place for future generations. To most environmentalists, the data suggest that the planet is already overpopulated. Because of differing concepts of carrying capacity, however, experts differ widely over what level of population is considered too high.
Some project that if everyone existed at a minimum survival level, the earth could support 20 to 48 billion people. This anthill existence would require that everyone exist only on a diet of grain, cultivation all arable land, and mining much of the earth's crust of a depth of 1.6 kilometers (1 mile). Other analysts believe the earth could support 7 to 12 billion people at a decent standard of living by distributing the world's land and food supply more equitably and shifting from less abundant resources (such as lead, tin, uranium, oil, and natural gas) to more abundant resources (such as aluminum, glass, and various forms of solar energy).
Others opposed to population regulation feel that all people should have the freedom to have as many children as they want. To some, population regulation is a violation of their deep religious beliefs. To others, it is an intrusion into their personal privacy and freedom. To minorities, population regulation is sometimes seen as a form of genocide to keep their numbers and power from rising.
Proponents of population regulation point to the fact that we are not providing adequate basic necessities for one out of five people on Earth today who don't have the opportunity to be a net economic gain for their country. They see people overpopulation in MDCs (more developed countries) as threats to Earth's life support systems for us and other species.
These analysts recognize that population growth is not the only cause or our environmental and resource problems. They believe, however, that adding several hundred million more people in MDCs and several billion more in LDSs (less developed countries) will intensify many environmental and social problems by increasing resource use and waste, environmental degradation, rapid climate change, and pollution. To proponents of population regulation, it is unethical for us not to encourage a sharp drop in birth rates and unsustainable forms of resource use to prevent a sharp rise in death rates and human misery and a decrease in Earth's biodiversity in the future. Despite promises about sharing the world's wealth, the gap between the rich and poor has been getting larger since 1960. Proponents of population regulation believe this is caused by a combination of population growth and unwillingness of the wealthy to share the world's wealth and resources more fairly. They call for MDCs to use their economic systems to reward population regulation and sustainable forms of economic growth instead of continuing their unsustainable forms of economic growth and encouraging LDCs to follow this eventually unsustainable and disastrous path for the planet.
Recently, the Population Crisis Committee complied a human suffering index for each of 130 countries based on ten measures of human welfare. They found a high correlation between the level of human suffering and the rate of population increase in countries. The 30 countries falling in the extreme human-suffering range--all in Africa and Asia--averaged a high annual rate of population increase of 2.8%. The 44 countries with a high human suffering rate--all in Africa, Asia, and Latin America--also had an average annual population increase of 2.8%.