"One day, sometime around the middle of this century, during the lifetime of people now alive, the population of the planet will be smaller than it was the day before. Global population growth is slowing, will level off, and one remarkable day, decline."Writing in "Significant Figures," Peter Gleick nails it. Where we are as a species on that day, which lies within many of our lifetimes, will determine whether or not humanity moves forward to evolve in safety and health.
In 2006, the United Nations stated that the rate of population growth was visibly diminishing due to the ongoing global demographic transition. If this trend continues, the rate of growth may diminish to zero by 2050, concurrent with a world population plateau of 9.2 billion.
Where women control their own bodies and have access to reproductive health, they tend to choose smaller families. However, in poor countries some 200 million women would like to delay their next pregnancy or stop having children altogether—but because of gender inequality or lack of access to information or services, they can't do that.There is a definite distinction among population groups which clearly impact on the environment in different ways. For the most part, countries with high rates of poverty and population growth contribute relatively little to greenhouse gases and other irreversible global ecological threats. This is not always taken into consideration in looking at the effects of population growth on greenhouse gas emissions.
In the long term, lower fertility in low-income countries will result in some reduction of global greenhouse gas emissions. However, lower fertility usually is associated with economic development, including urbanization. Unless low-income countries follow new, low carbon paths of development, higher standards of living will lead to higher per capita greenhouse gas emissions. The usual trend toward smaller household sizes as development proceeds will also tend to increase per capita emissions for a given population size.This is our challenge as we move forward to solve our environmental crisis: to reduce consumption of our planet's resources in highly developed nations and to assist developing countries to transition growth to new, low carbon paths of development.