For most of human history the population of the world was growing with less than 0.01% per year. In fact, since the homo sapiens started to move out of Africa some 50,000 to 60,000 years ago, the human population only increased from a few hundred thousand individuals to between 133 and 330 million individuals at the year 1 of our Gregorian Calendar.

Only during the agricultural and industrial revolution in Europe and Northen America the world population increased significantly. Typical growth rates during that period were in the range of 0.5% to 1.0% - at the maximum.

However, since the 1950s we observe much higher rates of population growth in Asia, Africa and Latin America which sometimes exceed annual growth rates of 3% or even 4% (see: Figure 1). Such high rates of population growth have also occured in populations with several dozend or several hundred million individuals.

While population growth rates of below 1% may be quite benign, there are numerous economic, social and political problems related to much higher growth rates (see: diagram 1).

The food production may not be able to keep up with such rapid population increase. This is a particular challange for peasant societies which depend on subsistence farming. Such agricultural systems are typically adapted to a particular ecological niche, which prevents easy expansion of arable land or rapid increase in productivity. When this balance of people and land is disturbed by rapid population growth, only commercial food markets or food aid can supply the increased demand. A typical example is the rapidly growing population of Egypt, which can no longer supply itself from the small fringe of fertile land along the Nile and depends on international food supply.

The education system may not be able to keep up with the rapidly increasing numbers of school-age children. Especially in poor countries with lacking administrative capacity it is rather difficult to organize the training of additional teachers, construction of schools, and preparation of school books and teaching materials under the condition of rapid population growth. Extremely high population growth has certainly contributed to the education disaster and insufficient vocational training in large parts of Africa.

Political stability may suffer in a country with high population growth - especially when the country is already densely populated. Social, ethnic, racial, religious or political tensions may flare up as the various groups compete over resources. The genozide in Rwanda and Burundi is certainly related to the fact that these countries had very high rates of population growth with farmers and cattle rangers competing for scarce lands.

International relations may be stressed due to excessive population growth - particularly when high rates of population growth occur in countries with scarce natural resources. People may be forced to emigrate into neighboring countries in search for work, water, ranging grounds or arable land. Boarder conflicts and international tensions may rise. While the current refugee crisis in Europe is primarily driven by violent conflicts in Syria, Afghanistan or Iraq, there are also young people from sub-Saharan Africa that try to escape from poverty and unemployment - conditions, that are at least partially caused by explosive population growth.

Environmental degradation is often a consequence of rapid population increase. In order to sustain a growing number of people the natural environment is increasingly being polluted, degraded or destroyed. Natural land cover is changed - often unreversible - due to agricultural expansion, hydropower dams, open pit mines, transportation infrastructure and expansion of settlements. Areas of rapid population growth (and high population density) are typically suffering extreme environmental problems - such as the horrendous air pollution in the urban agglomerations of China and India.

High vulnerability to natural disasters is associated with rapid population increase. People tightly packed into urban slums or unsanitary housing districts are particularly vulnerable to natural disasters and health problems. Flooding, land-slides, air-pollution or tropical hurricanes can cause millions of casualties in areas where population growth has created enormous (urban) concentrations of people - such as in Bangladesh, India, Eastern China and many other parts of Asia, Africa and Latin America.