The 21 st century is a critical period for people and the planet. The global population reached 7 billion during 2011 and the United Nations projections indicate that it will reach between 8 and 11 billion by 2050.
Human impact on the Earth raises serious concerns, and in the richest parts of the world per capita material consumption is far above the level that can be sustained for everyone in a population of 7 billion or more. This is in stark contrast to the world’s 1.3 billion poorest people, who need to consume more in order to be raised out of extreme poverty. The highest fertility rates are now seen primarily in the least developed countries while the lowest fertility rates are seen in the more developed countries, and increasingly in Asia and Latin America. Despite a decline in fertility almost everywhere, global population is still growing at about 80 million per year, because of the demographic momentum inherent in a large cohort of young people.
The global rate of population growth is already declining, but the poorest countries are neither experiencing, nor benefiting from, this decline. Population and consumption are both important: the combination of increasing global population and increasing overall material consumption has implications for a finite planet. As both continue to rise, signs of unwanted impacts and feedback (eg climate change reducing crop yields in some areas) and of irreversible changes (eg the increased rate of species extinction) are growing alarmingly.
The relationship between population, consumption and the environment is not straightforward, as the natural environment and human socioeconomic systems are complex in their own right. The Earth’s capacity to meet human needs is finite, but how the limits are approached depends on lifestyle choices and associated consumption; these depend on what is used, and how, and what is regarded as essential for human wellbeing.