Botkin Environmental Science Earth as Living Planet 8th txtbk

76 CHAPTER 4 The Human Population and the Environment
CRITICAL THINKING ISSUE
Will the Demographic Transition Hold
in the United States?
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Robert Engelman, Vice President of the Worldwatch Institute, “World Population Growth:
Fertile Ground for Uncertainty,” 2008.
Although the average woman worldwide is giving birth to fewer children than ever before, an estimated 136
million babies were born in 2007. Global data do not allow demographers to be certain that any specific year
sets a record for births, but this one certainly came close. The year’s cohort of babies propelled global population
to an estimated 6.7 billion by the end of 2007.
The seeming contradiction between smaller-than-ever families and near-record births is easily explained.
The number of women of childbearing age keeps growing and global life expectancy at birth continues to rise.
These two trends explain why population continues growing despite declines in family size. There were 1.7
billion women aged 15 to 49 in late 2007, compared with 856 million in 1970. The average human being
born today can expect to live 67 years, a full decade longer than the average newborn could expect in 1970.
Only the future growth of the reproductive-age population is readily predictable, however: all but the
youngest of the women who will be in this age group in two decades are already alive today. But sustaining
further declines in childbearing and increases in life expectancy will require continued efforts by governments
to improve access to good health care, and both trends could be threatened by environmental or social
deterioration. The uncertain future of these factors makes population growth harder to predict than most
people realize.
SUMMARY