Home About IEF Conferences Newsletter Resources e-learning centre on sustainable development IEF SUSTAPEDIA AN ENCYCLOPEDIA OF SUSTAINABILITY

One of the most important challenges to sustainability is the phenomenal growth in both human population and in levels of per-capita consumption over the last century.  The median United Nations projection suggests that the world will have to find space, resources and means of livelihood for some 9 billion (thousand million) people by the middle of the twenty-first century, that is, within the lifetimes of children living today.  This means that the world will be half again as crowded as it is now, and will require a great increase in the consumption of resources, even assuming no improvement in the living standards of the half of the world population that is desperately poor.  It also assumes that our present unsustainability does not trigger wars, epidemics, or economic or environmental catastrophes causing mass mortality in the decades ahead.  

It is not just the numbers of people that are important. Their impact depends on the rate of population growth, the level of consumption, the distribution of people relative to resources, the total sustainable population (carrying capacity) of the planet, and the implications of increasingly-crowded conditions on our well-being and quality of life.

Many problems associated today with population growth result, in fact, from the rate of growth.  Each human being requires food, housing, schooling, employment, health care and other resources and facilities. In a stable population, each new generation just replaces the one before, so that the requirement for facilities and jobs remains constant.  However, in a growing population, there is a continuing need for new school-rooms and teachers, more water supply, increased land for food production, additional housing, new jobs, and all the other things that people require.  These involve a significant capital investment and growth in human institutions.  When the population grows more rapidly than the society can afford to invest, then the existing social infrastructure must accommodate more people, diluting the amount per person and reducing the average quality of life.  If there is an unequal distribution of resources in the society, the rich and powerful will maintain their living standards, but the number of poor will increase.  The highest population growth rates today are in the disadvantaged populations and in the poorest countries, which can least afford to invest.  The result is mushrooming urban slums filled with those desperate for a better life, and an increasing number of rural poor whose numbers have outstripped the capacity of traditional agricultural systems leaving degraded landscapes.  Even in wealthy countries with lower population growth rates but higher per capita consumption rates, governments are falling behind in their ability to provide more housing, transport, employment, recreation, waste disposal, etc. (Dahl, 1996).

Under-capitalized population growth, where the necessary investment has not been made to make people productive members of society with their basic needs fulfilled, represents a kind of debt or social deficit.  Most societies accept the obligation to educate children and to give everyone opportunities for employment and self-advancement.  Such principles are enshrined in the universal declarations of human rights.  These investments in human capital are seen as essential for wealth creation and social and political stability in advanced democratic societies.  Each person who is uneducated or under-educated, who is poorly housed or under-employed, represents so much wasted potential.  The difference between that person's actual state of ignorance and poverty, and the state of education and well-being to which he or she should have a right as a human being, is as much an accumulation of debt as the loans that most countries must repay to foreign creditors.  Today, we are equally likely to default on both kinds of debt (Dahl, 1996).

The increasing density of the human population directly affects our well-being and quality of life.  Experiments with caged colonies of rats show that increased crowding leads to many forms of aggressive and deviant behaviour, not unlike those observed in cities. The lack of access to peace and quiet, nature and beauty, wilderness and solitude may contribute to this.  Megacities are growing explosively all over the world, and half the world population now lives in urban areas. Yet people are continuing to crowd into cities just when the new technologies of communications and transportation are making it less and less necessary to be in physical proximity in order to carry out the business of the modern world. Cities have enormous ecological footprints, with impacts far beyond the urban area. The concentration of pollution and wastes, the spread of diseases due to overcrowding, the time and energy wasted in long commutes and traffic jams, the nervous stress from noise, crime, and over-saturated senses, all reduce sustainability and quality of life in what may best be described as an over-developed civilization (Dahl, 1996).

The numbers of people cannot be considered in isolation from their rates of resource consumption.  A single individual in an industrialized country may consume two hundred times the resources of one in a poor country, and thus have a proportionately larger impact on the environment.  Thus, even a small population increase in a wealthy country can be much more significant in terms of global sustainability than a higher increase among the poor.

The demographic transition, when rapid population growth is followed by stabilization due to a sharp decline in the birth rate, as has happened in many countries, creates another problem, often accentuated by an increase in life expectancy.  Most social welfare systems depend on revenues from the working population to support the elderly, for whom social services and medical expenses can be very high.  If, because of changing birthrates and reduced mortality, the number of aged increases while a smaller work force is left to support them, then a crisis in social welfare will result.

Finally, the world population distribution today is out of balance with available resources. Some countries have excess populations they cannot support, while others with low birth rates and ageing populations lack young workers. The proponents of globalization have eliminated all barriers to the movement of capital, and are working to free up the global trade in goods and services, yet they refuse to consider the other essential dimensions of globalization, the free movement of people. If the world has become one country and all humanity its citizens, then immigration controls, passsports and visas need to fade away. While it might seem logical to move excess populations to wealthier countries which have the resources to support them, any discussion of such population movements between countries seems to be anathema. Industrialized countries worried about their declining birth rate may offer fiscal incentives to their citizens to have more children, but they would never consider filling depopulated rural villages with excess Chinese or Africans. Immigration is too politically sensitive. Yet the problem can only get worse. Economic and environmental pressures and political crises will increase the numbers of migrants and refugees in the years ahead. Climate change and related sea level rise may create millions of additional refugees. The burden of resettling all these people needs to be distributed equitably. The world may need a mechanism similar to the World Trade Organization to assist nations in removing barriers to the free movement of people equitably and gradually, allowing for the necessary adjustments in society.