Fifty years ago the world's population was about 2000 million. Now (2011) it is about 7000 million and still rising at the rate of about 92,000,000 annually. It increased by 5 times during the course of the 20th century. This has profound implications for the state structure which was formed at a time when the population was much smaller than it is now. Some schools of political thought praise "minimal government" as devised in the 18th century. But the minimum government operated among very small populations. Most of the statesmen of today were born into a world of 2000 million. Their fathers thought in terms of 1000 million. The very dense populations of today must require more co-ordination and planning than thin rural communities.

New foods
What has been the main cause of population growth? Despite Malthus's gloomy thoughts on the matter, human populations have always increased as a response to new sources of food. Thus the agricultural revolution made possible a huge increase as a result of growing food in farms instead of collecting it from the wild lands (but there was also the arrival of new diseases caught from animals, and hugely increased work loads). (see Mithen) The arrival of new crops from the Americas, especially maize and potatoes, triggered increases wherever they were adopted. In Europe potatoes were the main stimulus to increase, from the late 18th century. In Africa maize triggered increases wherever it was suitable to grow.

In Uganda the arrival of the banana from Indonesia caused political changes and the growth of a new population and kingdom in Buganda - an area ideally suited to growing bananas and unsuited to the previously existing crops.

Oil
In the 20th century food production has expanded mainly because of the use of oil - to power machinery and to make fertilisers. As oil begins to run out, what will be the effect on agriculture? Many of the current farms and other producers are dependent on cheap energy. Can the same amount of food be grown with renewable energy - mainly solar derived?

Political effects of large populations
Political theorists have suggested that the ideal political society in which democracy can flourish must have a small population. The United States federation was formed with a population of 4 million or so. Now it has 300 million.

Is there an optimum population for the world? Or can it increase indefinitely? Those who have an optimistic mood but lack data claim that numbers can continue to increase and be supported with food, energy and other necessities.

Those with more data tend to believe larger numbers will be unsupportable except, possibly, at a very low standard of life. Biologists observe that all species tend to increase in numbers up to the limit of their food supply. Usually they overshoot and the population then falls with a "crash". The British economist and clergyman, Thomas Malthus, who first pointed this out, wrote at the beginning of a great increase in food supply, which he did not foresee - the opening up of the American grainlands. He was therefore apparently discredited. The world population in his day may have been no more than about 1000 million. Is there another source of great increase of food production in prospect for the medium term future? Few believe it likely.

Jacques Cousteau, the French scientist, calculates that the planet can support sustainably only about 700 million people at the economic level found in western countries.

It is possible that the human population has already passed the numbers which can be supported on income resources (solar energy without mining). Research is needed to find out whether this is the case.

Model designers have shown that the very complex world economy has many inter-relationships. Rise in population tends to increase the amount of pollution which at high levels affects food production, and is already doing so. Very intensive agriculture requires large inputs of energy. Modern agriculture needs a large industrial supply system which itself uses energy and produces pollution.

Increased population requires and will require agriculture to spread on to land which is not suited, such as hill slopes, unreliably watered land and land needed for climate-regulating forests. Much of modern agriculture has the character of a mining industry - reducing soil fertility to produce food - living on capital rather than income.

Several present wars or civil disturbances, especially in Latin America, India and Sri Lanka, seem to be being made worse by population increase and competition for land. Several countries show signs that increased density of population is causing conflict in populations of mixed culture who previously lived peaceably together. Rwanda and Burundi are examples.

In the Middle East increased population presses on the water supply which can lead to probable future wars. In the South West of the United States increased population also presses on the water supply and causes political disputes.

Concern about the present size of the world's population and its rate of increase should not be directed solely at the poor. The number of the rich consumers is a problem at least as great. A policy of standstill for both sides is necessary and if it can be achieved discussions of a reduction might be appropriate (but see Fred Pearce).

The ecological effect of the number of people is composed of the numbers times the rate of consumption. Thus both these factors need to be tackled simultaneously.

The following countries are believed to have an especially difficult population problem: Bangladesh, Brazil, Burundi, China, El Salvador, India, Pakistan, Rwanda, Sri Lanka, Philippines(almost entirely because of religious irrationality). All the European industrialized countries and Japan are overcrowded by world standards and exist only on imported resources. In several countries an effect of rapidly increasing population is the existence of street children living by crime and in danger of early death. Colombia, Mexico, Brazil, Kenya, South Africa.

Population is increasing rapidly in Africa. Landless people are appearing in Kenya, where ethnic conflict has begun, spectacularly in January 2008.

However, Singapore and Malaysia have a policy of increasing population - but the people may reduce family size anyway.

Since the above was written in 1990 it has become clear that Climate Change is going to make the population problem far more serious. Rising temperatures are likely to reduce overall food production and therefore the number of people that can be supported. The events of 2010 show that a reduction of food supplies can occur. Deviation of the Jet Stream caused drought, crop loss and forest fires in Russia, severe monsoon flooding in Pakistan and China and floods in Niger, West Africa. All these caused deaths, and the loss of Russian wheat puts the world very close to famine from lack of wheat.

Food production in 2012 is going to see a reduction. In North America a drought will reduce harvests. In Europe heavy rain will also reduce harvests. The weather disturbance is almost certainly a symptom of rising carbon dioxide levels.

Sociological effects of over-population
For thousands of years, perhaps for most of human history, population has increased either slowly or not at all. Death rates and birth rates roughly balanced. Groups which experienced high death rates tended to have larger families, in the hope that enough to replace those who died will survive. This can be seen especially in Africa.

There is an epidemic of child killing in the Niger Delta states of Nigeria on the excuse that some of the children are "witches". Is this a sign that because each new child is a burden on the parents they are not valued and "religious" reasons are being found to make it acceptable to let them die, or even to kill them? We can contrast this to the culture in modern China where the government encourages one child per couple. Those that are born are treated like "Little Emperors".

Can the massacres in Rwanda be attributed to over-population? If so, the religious leaders who oppose sensible methods of preventing births are partly to blame for making the situation worse.

History of population

wikipedia

Alan Weisman - The World without us
an intelligent meditation on the problem. He suggests an extension of the China 'one child policy' to the whole human community.

Peoplequake: Mass Migration, Ageing Nations and the Coming Population Crash

Peoplequake

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This is the big one and the key to all the other problems.

Religion
If you can find out how to square the Pope and the Ayatollahs you deserve a Nobel prize. Both resist any talk of contraception. (But Cousteau notes that Catholic Italy and Spain have very low birth rates and Indonesia, the largest Muslim country, has reduced its birth rate after campaigns). In fact four religions contain groups that encourage very large families: Catholic policy is against contraception (despite there being no mention of it in their bible); some Orthodox Jews also encourage large families; some (but not all) Muslims are against contraception. Mormons, too, especially dissident groups, encourage large families.

The second Bush regime (2001-2009), responding to "religious" lobbying banned US government assistance for contraception. It is likely that the incoming Obama regime will cancel this opposition.

The human species is in the same position as the New Zealand flightless parrot, the Kakapo. Because it too had no predators it evolved a very low birthrate to prevent it using up the food supply. (Unfortunately it has predators now and its birthrate is now too low).

Mathematically, there are only two solutions. One is to increase the death rate until it is equal to or above the birth rate. We have the means to do this. Your local airfield may well possess them. It should go without saying that this method should not be chosen but it may occur if the problems associated with population growth result in general war and famine.

The other is to reduce the birth rate until it is at or below the death rate, to match the actual food supply. We have the means for this too and could do it if we had the will. Several European countries, notably Germany and Italy have already achieved this condition with a slowly decreasing population (offset by immigration). But there are important cultural tendencies which may prevent knowledge about the means being spread (see Religion), mainly in the third world.

The evidence is that reductions to the birth rate are best made by educating and providing employment for women. Those countries which have achieved a lower birth rate are those which have invested in education and economic development. Japan is one of the most notable examples of a society which has been transformed quickly from a high to low birth rate. Kerala in India has also achieved a stable population with a high standard of education and welfare provisions, though with a low average income. This is encouraging as the country has a large proportion of Roman Catholics. (Italy and Spain have also achieved very low birth rates.)

The countries with the highest birth rate are those with the lowest productivity and education. (See Imbalance). These find it difficult to invest enough to raise the standard of living. A feedback to this is that populations with a rapid rate of increase cannot accumulate capital.

Opposite Trends
AIDS may raise the death rate, but the epidemic is in too early a stage to know whether this rise will be significant. Some central African countries are believed to be about to experience a population reduction because of AIDS, and as it seems to attack the educated and managerial population especially severely this will worsen their standard of development.

A rise in the death rate from disease usually provokes a rise in the birth rate to compensate, thus any population fall might be filled up quickly if social habits adapt. There are too many unknowns - rate of infection, change of habits, possibility of prevention - to make reliable calculations of the effects of AIDS, which in any case is not affecting the western industrialized countries to any great extent, yet.

Another trend is emerging in India, where there is strong pressure to have sons rather than daughters (marriage costs and dowries go from the family of the daughter). The spread of ultra-sound machines leads to the abortion of female fetuses. Already an imbalance of more males than females (133 to 100) is noted. This will have the unintended effect of reducing the birth rate. (No-one knows what the frustrated excess males will do when they can't get married. Perhaps prostitution and AIDS infection will increase. Possibly Polyandry will increase - one woman marrying two or more brothers) China also shows a drop in the ratio of women (2 to 3). AIDS kills more women than men in some African countries.

Are modern human beings immune from the general mathematical model of populations controlled by availability of resources? A useful example can be found among the Mayas of Central America where populations crashed about in about 1200 CE when soil became exhausted. See Mexico and Guatemala.

Pollution
There is some evidence that certain chemicals (DDT, PCB, DDE, Phenols) which mimic female hormones have been released into the environment and are reducing male sperm output. Is it only a Science Fiction horror to imagine a period when human reproduction will be as badly impaired as that of alligators in a Florida swamp? In which case the worry would be of extinction rather than over-population.

The possible end of the efficacy of antibiotics would raise the death rate as bacterial disease can no longer be treated (after 60 years of success since the 1940s).

The latest UN figures suggest the rate of increase is slowing and final figures will be less than the highest forecasts. This is probably caused by the decline in fertility in several countries. However, the other aspects of the Problematique show no signs of easing.

Many students of the Problematique are rather pessimistic and say, at least privately, that a huge population crash is highly likely - billions of deaths.

Religion
Religious people tend to quote the bible as saying: increase and multiply, without noticing that this advice was given at a time when the human population was much smaller than now (perhaps reduced after the retreat of the ice 10,000 years ago). What a pity the advice was not in the form of a computer algorithm:

• while totalpop<1000 million
•     increase and multiply
• endwhile

That is, the advice was only good up to a point. It needs to be replaced with a new algorithm:

• while totalpop >1000 million
•     one child per couple
• endwhile

That is, a worldwide policy of smaller families is needed until the population is down to a level that can be supported with only low levels of resource depletion. The slogan would be fewer children, but better - each one to be properly educated. In the areas with very large birth rates children tend to be neglected to the point of having a high death rate and being exploited as child labor, and worse.

Solution 2010?
It seems possible that there is already a trend towards smaller families that may reverse the growth trend during this century. Here is an article by Fred Pearce that suggests this. People who move into cities have throughout human history had fewer children than those in the rural areas - and even rural families are getting smaller. Of course this trend also points to an aging population - a greater proportion of older people.

Some useful notes on the optimum population (much less than at present).