Population

The impact of the population explosion on the environment

Use of contraception has increased from less than 10% in the 1960s to more than 60% in the 21st century.

Professor, Department of Biology, Chair, Natural Capital Project, Stanford University Stanford, California

FIGURE

History of world population growth

Source: Population Reference Bureau; United Nations, World Population Projections to 2100 (1998).

Population size is clearly an important factor in measuring environmental impact. With the use of contraception and increased education, the world fertility rate has dropped from 4.5 children per woman in the early 1970s to 2.7 in the early 2000s. 2 Much of this change resulted from the efforts of health professionals to provide contraception to women who desire it. In fact, use of modern contraception increased from less than 10% in the 1960s to more than 60% in this decade. 3

Fertility rates remain closely associated with level of development. As the percentage of a nation’s population living on less than $2 per day increases, so does its fertility rate. 4 Similarly, as the gross domestic product per capita increases, the population growth rate declines. What is true among nations is also true within populations: With increasing wealth, fertility rates decline. 5

Contraceptive use is also strongly correlated with individual and national wealth. 6 However, data from international family planning programs show that strong government support can improve access to contraceptive services among the poor. In Bangladesh, for example, which has a strong national family planning program supported by international aid, 45% of the poorest women and 50% of the wealthiest women use modern contraception. 4 In contrast, only 5% of the poorest women in Guatemala use contraception compared with 60% of the wealthiest. However, other factors, such as education and religious beliefs, may also play a role in contraceptive use.

It may not be surprising that low levels of education are associated with low rates of contraceptive use and high fertility rates. 7 It is important, though, to recognize that many widely held goals—such as equity between males and females and improvements in health, access to education, and standards of living—are associated with low birth rates.

Population is just one factor in evaluating environmental impact. Other multipliers in this equation are level of affluence—measured as consumption per person—and unit of consumption, reflected in the technologies used to supply energy, food, and other resources. For example, the United States has slightly less than 5% of the world’s population yet accounts for more than 30% of environmental impact by most metrics. This estimate considers not only the direct effects of the US population, but also the level of influence the United States has on the practices and technologies used worldwide. Furthermore, among developed nations, the United States has one of the most rapidly growing populations, at a rate of 1%. By comparison, the populations of many European countries are not growing at all and some are even shrinking. 2

Family planning and the creation of nature preserves are strategies that have been used for environmental protection, but it is becoming apparent that this is not enough to effectively sustain Earth’s life-support systems. The challenge is to develop 21st century approaches that integrate human needs with environmental protection. Pioneering efforts are underway, directing resources to help ensure that pregnancies worldwide are planned, while creating new livelihood strategies that harmonize human activities with conservation. There is a long way to go, and no greater challenge for civilization.

Sexuality, Reproduction & Menopause ©2009 Quadrant HealthCom Inc.