The dangers of a population explosion have been all over the newspapers lately and indeed the world population could reach seven billion in just two years and eight billion perhaps in the next two decades. But that’s not the only story. Dramatic declines in fertility rates in some countries and high rates in others pose a critical challenge. One must be reminded that the growth of world population — which now stands at an estimated 6.8 billion human inhabitants — has greatly impacted all life forms and the overall natural environment of the planet.
　　Although the population of the world continues to grow substantially — 79 million per year — the rate of growth has declined by nearly half over the last 40 years – from 2 percent to 1.2 percent a year. The cause for the slowdown is declining fertility rates. However, while the average global fertility has dropped from about 5 to 2.6 births per woman during the past 50 years, considerable uncertainty exists about the future. Insofar as fertility is the engine driving the future size of world population, this uncertainty about the path of fertility in the coming years is one of the central and challenging questions of this century. (199)
　　近来，关于人口爆炸危害的报道铺天盖地，不过的确，世界人口在仅仅两年内就有可能达到70亿，并在未来的20年里增至80亿。然而，这并不是事情的全貌。有些国家出生率大幅下降，而有些国家却保持高增长率，这就带来了严峻的挑战。我们要警醒，世界人口当前估约68亿，其增长给地球所有生命和整体自然环境都带来了重大的影响。
　　尽管世界人口总量以每年7900万的速度持续大幅增长，然而，在过去40年里，增长率却下降了约一半，从原来的每年2%下滑到了1.2%。增长放缓原因来自出生率的下跌。不过，虽然过去50年全球平均出生率从每位妇女约生5个孩子降到了每位妇女2.6个孩子，世界人口的前景却极不明朗。出生率一直是决定世界人口潜在规模的动因，因此，未来几年出生率曲线走向的不确定性就成了本世纪最关键最具棘手的人口问题。