Human society is faced with an historically unique period of population growth, due to a dramatic decline in death rates coupled with constant fertility rates in much of the world. The world now produces one million more members of the human family every 96 hours. The momentum of population growth is so great that is difficult to slow down and it is unlikely to cease in forthcoming decades.
Although there is some convergence of death rates between developed and developing countries, there remains nevertheless a substantial fertility differential. Population growth thus results from the unbalanced acceleration of a long transitional process from the high birth and death rates that characterized most of human history to the low birth and death rates which characterize society today. The process is now in disequilibrium because the achievement of lower mortality has taken effect without any corresponding achievement of lowered fertility.
The combined effects of increasing world population and of per capita consumption are putting pressure on the limited resources of the planet and on the limited capacity of man's natural ecosystems for self-regulation and self-regeneration. This pressure will necessarily bring about, in a non-remote foreseeable future, a general readjustment of the relationship between man and his natural ecosystems, at the cost of a catastrophic decrease in world population, due to massive mortality, together with a major degradation of the material and cultural standards of humanity.
The situation has serious consequences for human values. Continued growth threatens both living standards and the environment in various ways. Population growth is a serious intensifier and multiplier of other social and economic problems, especially as it retards the prospects for development of a better life in the poorer countries, and aggravates environmental pollution and resource depletion by the richer ones.
Wars, famines and epidemics have occurred in various parts of the world in modern periods. Assessment of some of the effects of such calamities on past population trends has shown them to be considerable in the less developed regions during the second half of the nineteenth century, and in both the less developed and the more developed regions during the first half of the present one. Nevertheless it would be a fallacy to think that wars in modern times have significantly held population growth in check. It can be calculated schematically that all the national and regional disasters on record since 1850, terrible as they have been, have delayed the growth in world population by no more than about ten years. Had there been no wars, famines or epidemics since 1850, the world's population might have totalled more than 2.000 million in 1920 instead of in 1930, and more than 3,500 million in 1960 instead of in 1970.
The world's population totalled approximately 1,000 million in 1804. It took 123 years to add another 1,000 million; 33 years to reach 3,000 million in 1960, 14 years to reach 4,000 million in 1974, 13 years to reach 5,000 million in 1987 and 12 years to reach 6,000 million in 1999. The rate of population growth, though now beginning to fall, still adds nearly 80 million people a year, with 97 percent occurred in the poorest parts of the world.
During the first millennia of human history, population growth was negligible (0.002% per annum). By the middle of the eighteenth century, that rate had accelerated 150 times (to 0.3%, namely 3,000 per million). By the 1950s, the latter rate of growth had accelerated fivefold (to 1.5% or 15,000 per million). A peak of 2.2% (22 per million) was reached in the early 1960s and stayed above 2% for that decade. The 1970s saw a sharp fall to around 1.7%, which persisted through the 1980s. Since the beginning of the 1990s there has been a steady fall; at the turn of the century the rate of growth was around 1.3% per annum or 13,000 per million). The faster a population is growing, the shorter the time it takes to double in size. Whereas before 1650, world population took about 35,000 years (or about 1,400 generations) to double, at present rates it can double in just one generation. Some demographers project a doubling or even tripling of global population in the next 100 years, with most of the increase in the developing countries and most of that in the cities. The African sub-continent is the fastest growing region in the world with the highest fertility rates, doubling its population in 25 years.
Although the pace of overpopulation slowed down in the 1990s, the population explosion, along with food shortage, poverty and ageing, remains one of the essential problems of the future. Global totals masks considerable differences among individual regions and countries, which are growing at different rates; accelerating in some instances and slowing down in others. On August 15 2001, India is expected to pass the 1 billion mark, joining China in the unenviable 1 billion club. By no later than the year 2025, the combined population of Asia and Africa will be 6.5 billion, significantly more people than now live on the entire planet. The extra 3 billion or so people who must be housed, fed, clothed and educated, and who will most live in already overcrowded cities of developing countries, will substantially increase the threat to environmental, economic and social sustainability at the local, regional and global scale.
Revised long-term forecasts made in 1991 by the United Nations suggest that rather than reaching a stable population of 10.2 billion in the year 2085, the then population figure could double by the middle of the 21st century and stabilize at 11.6 billion.
Scenarios released by the IIASA in 1994 predict with certainty that by 2030, world population will increase by at least 50 percent (from 5,291 billion); it may even double in size in this time. A stable population of something over 12 billion may not be reached until around 2100. By 2030, today's developing countries will represent between 85 and 87 percent of the world population. Africa's share of world population will increase most rapidly. The average age of all world regions will also increase.
Because of the failure to come to grips with the problem of rapid population growth in previous years, three billion young people, equal to the whole population of the world as short a time ago as 1960, will enter their reproductive years in the next generation. At 2000: (a) 300 million women want and need family planning but lack either information or means to obtain it. (b) One billion people have no access to health care. Eight million infants under age one will die this year – 22,000 each day – many because their mother did not know how to allow appropriate intervals between pregnancies. (c) More than 600,000 women die every year because of complications from pregnancy and abortion, many because of unwanted pregnancies that could have been avoided through family planning. (d) At least 75 million pregnancies each year (out of a total of 130 million) are unwanted. They result in 45 million abortions and more than 18 million live births. (e) There are an estimated 333 million new cases of sexually transmitted diseases (STDs) each year. Worldwide, the disease burden of STDs in women is more than five times that of men. (f) 1.3 billion people live in absolute poverty – surviving on less than $1 per day – with roughly 600 million people homeless or without adequate shelter. (g) The number of rural women living in poverty in developing countries has increased by almost 50 percent over the last 20 years, to 565 million. (h) 85 countries are unable to grow or purchase enough food to feed their populations – 840 million people are malnourished. (i) 2.3 billion people live without adequate sanitation. (j) At least 1.5 billion people – nearly one-quarter of the world's population lack an adequate supply of drinking water. (k) Unemployment in many countries of the developing world is 30 percent or higher. 120 million people are actively looking for work; 700 million are classified as underemployed, working long hours, often at back-breaking jobs that fail to even come close to meeting their needs. (l) In 1950, only one city in the developing world had a population greater than 5 million; by the year 2000, there will be 46 such cities. (m) 600,000 square miles of forest were cut down in the 1990s. (n) 26 billion tons of arable topsoil vanish from the world's cropland every year. (o) Global climate change is disrupting weather patterns; causing more severe droughts and flooding, and increased threat to human health.