Published by Australian Academy of Science
Population and environment – what's the connection? Box 1 | Trends in world population

Only 200 years ago, the total world population was probably less than a billion. Today, it stands at over 6 billion.

From 1994-2004, the world population grew at a rate of about 1.3 per cent per year. This is down from 1.7 per cent in the 1970s and 1980s but the lower rate is applied to a much larger population. Population growth varies geographically across the globe with rates of 0.3 per cent in more developed countries compared with 1.6 per cent in countries that are less developed. Australia's current growth rate, including immigration, is 1.2 per cent.

Population size is influenced by the birth rate and the death rate

The two main factors that influence the size of the world's population are the birth rate (or fertility) and the death rate (or mortality). The main reason the world's population has increased so dramatically in recent centuries is because the mortality rate has declined. People live longer due to improvements in hygiene, nutrition and medicine. Importantly, a much higher proportion of infants survive the rigours of early childhood.

Because mortality has declined more rapidly than fertility, the world's population is increasing. Developed countries, including Australia, the United States, Japan and some European nations, have recently seen dramatic declines in fertility to a point where the natural increase in population (ie, excluding immigration) is virtually zero. They are said to have completed the demographic transition from a high fertility, high mortality population to a low fertility, low mortality one.

However, populations in many developing countries continue to increase. Many of these are about halfway through the demographic transition: mortality has declined significantly, but fertility remains high. Ninety-five per cent of the yearly population increase from 1994-2004 occurred in less developed countries.

The demographic transition gives us hope that the human population will be able to reach stability without disasters in the form of mass starvation or killer diseases. Education, particularly of women, improved living standards and access to contraception are important factors in achieving the transition.

Related sites

• Population growth coming to an end (transcript from PM, 2 Aug 2001, Australian Broadcasting Corporation)

• Human population growth (Biology by J.W. Kimball, USA)

• 2004 World Population data sheet (Population Reference Bureau)

• United Nations Population Information Network (United Nations)

• US and world population clocks (US Census Bureau)

Other boxes

Box 2. Exponential growth

Box 3. Immigration and population growth