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 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.
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: (1) 300 million women want and need family planning but lack either information or means to obtain it. (2) 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. (3) 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. (4) 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. (5) 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. (6) 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. (7) 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. (8) 85 countries are unable to grow or purchase enough food to feed their populations - 840 million people are malnourished. (9) 2.3 billion people live without adequate sanitation. (10) At least 1.5 billion people - nearly one-quarter of the world's population lack an adequate supply of drinking water. (11) 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. (12) 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. (13) 600,000 square miles of forest were cut down in the 1990s. (14) 26 billion tons of arable topsoil vanish from the world's cropland every year. (15) Global climate change is disrupting weather patterns; causing more severe droughts and flooding, and increased threat to human health.
2. In 1992, a joint USA/UK study concluded: If current predictions of population growth prove accurate and patterns of human activity on the planet remain unchanged, science and technology may not be able to prevent either irreversible degradation of the environment or continued poverty for much of the world.
3. Excessive population growth diffuses the fruits of development over increasing numbers instead of improving living standards in many developing countries.
4. Under certain conditions population growth may stimulate technological innovations or improvements. Such benefits may be outweighed by disadvantages when human institutions, market mechanisms and technology do not adapt quickly to changing conditions. Environmental circumstances may not favour innovations intended to respond to population growth, such as intensive agriculture in depleted soils which cannot support it.
5. On current trends the years to 2012 will see a world population increase of 2 billion, namely twice the 1992 population of China. It will be the largest population increase ever during a 20-year period and will put extreme pressure on developing countries where birthrates are generally high and resources are stretched most thinly.
6. During the next decade India and China will each add to the planet about ten times as many people as the United States will -- but the stress on the natural world caused by new Americans may exceed that from new Indians and Chinese combined. The expected 57.5 million new people added to the US population during the 1990s will add more greenhouse gases to the atmosphere than the roughly 900 million new people in developing countries.
7. [Homo sapiens] will keep growing in number, as everyone agrees, and that growth may have disagreeable consequences. But those consequences seem less likely to stem from the environmental collapse the apocalyptists predict than from the human race's perennial inability to run its political affairs wisely. The distinction is important, and dismaying.
2. Under correct economic conditions (such as public control of the means of production) population will take care of itself. The environmental consequences of population growth are due to the affluence and consumption of developed countries, which use up resources and produce pollution.
3. It is not the total numbers which are important, but rather their distribution over the land area. It is the concentration of people in urban conglomerations which is the real problem.
4. Population increase is advocated by some countries as a means of ensuring national sovereignty, and the minimum population requirements needed for a country to become a regional or world power.
5. The entire population problem and the solutions proposed for it pose fundamental questions in the moral and religious realm and may even introduce revolutionary upsets. Ideas such as freedom, happiness, justice and human dignity are put into question with no concern for what will replace them.
6. Overpopulation is a relative concept. It signifies that, at a given stage in international development, there is a surplus of manpower, in the sense that the productive margin of work in these regions is nil or so low that it is no incentive to work. The phenomenon can of course be attributed to exaggerated population growth, but is also, more than anything else, a consequence of the endemic inadequacy of the stock of capital worldwide.
7. On average, standards of living have improved throughout the world. Between 1960 and 1990, as world population went from 3 billion to 5.3 billion, infant mortality dropped and life expectancy, literacy, per capita income, food production and nutrition all increased.
8. The United Nations projects world population to grow from 6.1 billion in 2000 to 9.4 billion in 2050, with all of the additional 3.3 billion coming in the developing countries. However, it is doubtful that these projections will materialize as population pressures increasing transform routine management situations into full-scale humanitarian crises.
9. Within 20 years the AIDS epidemic may turn current high population growth rates negative. For example, in Uganda, where 1.5 million people out of a population of 16 million were thought to be HIV positive in 1992, the (then) 3% population growth rate could fall to below zero after 2002 (with more people dying than being born). This means that by 2007, Uganda would have 20% fewer people than if the AIDS epidemic had not occurred. The population would be 20.3 million instead of 24 million. Tanzania, Malawi and Rwanda, all in the Central and East African belt where AIDS has hit hardest, would be similarly affected.
10. How can economic development and the supply of food keep pace with the continual rise in population? This is a question which constantly obtrudes itself today -- a world problem, as well as one for the poverty-stricken nations. As a world problem, the case is put thus: According to sufficiently reliable statistics the next few decades will see a very great increase in human population, whereas economic development will proceed at a slower rate. Hence, we are told, if nothing is done to check this rise in population, the world will be faced in the not too distant future with an increasing shortage in the necessities of life. As it affects the less developed countries, the problem is stated thus: The resources of modern hygiene and medicine will very shortly bring about a notable decrease in the mortality rate, especially among infants, while the birth rate -- which in such countries is unusually high -- will tend to remain more or less constant, at least for a considerable period. The excess of births over deaths will therefore show a steep rise, whereas there will be no corresponding increase in the productive efficiency of the economy. Accordingly, the standard of living in these poorer countries cannot possibly improve. It must surely worsen, even to the point of extreme hardship. Hence there are those who hold the opinion that, in order to prevent a serious crisis from developing, the conception and birth of children should be secretly avoided, or, in any event, curbed in some way. Truth to tell, we do not seem to be faced with any immediate or imminent world problem arising from the disproportion between the increase of population and the supply of food. Arguments to this effect are based on such unreliable and controversial data that they can only be of very uncertain validity. But granting this, We must nevertheless state most emphatically that no statement of the problem and no solution to it is acceptable which does violence to man's essential dignity; those who propose such solutions base them on an utterly materialistic conception of man himself and his life. The only possible solution to this question is one which envisages the social and economic progress both of individuals and of the whole of human society, and which respects and promotes true human values. First consideration must obviously be given to those values which concern man's dignity generally, and the immense worth of each individual human life. Attention must then be turned to the need for worldwide co-operation among men, with a view to a fruitful and well-regulated interchange of useful knowledge, capital and manpower. (Papal Encyclical, Mater et Magistra, 15 May 1961).