If we apply to our lives the rules we apply when managing other species, we should curb population growth well before human numbers reach our estimate of what the planet can support. This is particularly important because whilst we know that there is an ultimate limit to the planet's carrying capacity, we are uncertain exactly what it is.

* Commercial energy (e.g. coal, oil, nuclear) consumption is a useful measure of environmental impact. Energy enables people to take resources from the environment, to change them into usable products, and consume them. During this process waste is produced, and often released into the environment as pollution.

* The 42 countries in the world that use the most energy per person contain only one quarter of the world's population but account for four-fifths of its use of commercial energy.

* The 128 countries that use the least amount of energy per person contain three quarters of the world's population but use only one-fifth of commercial energy consumption.

* On average, a person in a `high energy consumption' country consumes 18 times the commercial energy used by a person in a 'low energy consumption' country, and causes twice as much pollution. One North American causes the emission of twice as much carbon dioxide (see Enviro Facts "Global Warming") as a South American, and ten times as much as someone in South or East Asia (excluding Japan).

* Although most `high energy consumption' countries have near- stable populations (i.e. the population growth is close to zero) their resource consumption continues to rise.

* Where there is poverty people have less security and fewer choices. It seems that with economic growth and the range of options it brings, people, particularly women, choose not to have large families.

Economic growth and a widespread distribution of the benefits it can bring, creates jobs and improves education and health facilities. With improved education facilities, more women will have opportunities to attend school. More jobs means that women, drawn into the growing job market, become wage earners in their own right. New found status and empowerment resulting from earnings and education, coupled with access to family planning services, allow women greater control in deciding how many children they will bear. A desire to remain employed, and fewer child deaths (as a result of better health services) no doubt contribute to a decision to limit the number of children born.

* In some societies, where financial structures such as pension and retirement annuity schemes are not readily available, having children is a rational choice as they provide security for their parents' old age.

Giving people the means (through the vote, improved social and legal status, education, access to family planning and financial independence) to choose the size of their families will not only help keep the population in balance with resources; it is also a way of assuring, especially for women, the basic right of self- determination.

Concern over population growth is a call of concern for human progress and human equality.

* South Africa's estimated population of 41,7 million is growing at a rate of 2,6% each year, making it set to double within the next 25 years.

* For sustainable living all societies need a balance between resources and population. Could it be argued that in South Africa the balance has been destroyed by colonial and apartheid policies and through this process, major environmental problems have been created? Thus it is not population numbers that threaten the South African environment, but the lack of access to resources on the one hand and the overconsumption of resources on the other.

* In South Africa, is poverty a result of having too many children - or are large families a symptom of poverty?

OUR COMMON FUTURE. World Commission on environment and development. Oxford University Press, Oxford, 1987

UPROOTING POVERTY: THE SOUTH AFRICAN CHALLENGE. F. Wilson and M. Ramphele (eds). David Philip, Cape Town, 1989.

BACK TO EARTH. J. Clarke. Southern Books, Johannesburg, 1991.

GOING GREEN: PEOPLE, POLITICS AND ENVIRONMENT IN SOUTH AFRICA. J. Cock and E. Koch (eds). Oxford University Press, Cape Town, 1991.

SOUTH AFRICAN ENVIRONMENTS INTO THE 21ST CENTURY. B. Huntley, R. Siegfried and C. Sunter. Human, Rousseau and Tafelberg. Cape Town, 1989.

All books available from Russel Friedman Books, PO Box 73, Halfway House, 1685. Tel. 011-7022300/1.

The Urban Foundation. PO Box 1198, Johannesburg, 2000. Tel. 011-403 5500.

The Rural Foundation. Drostdy Centre, PO Box 388, Stellenbosch 7600. Tel. 02231-76870.

Institute for Natural Resources. University of Natal, PO Box 375, Pietermaritzburg 3200. Tel. 0331-68317.

SAPLER (Splendidly alive people within limited environmental resources). PO Box 51446, Raedene, 2124. Tel. 011-640 7180.