1987年年中,地球上的人口达到了50亿人。在保持目前的增长速度(平均每年增长1.7%)的条件下,到2000年,地球上的人口将超过60亿人;而到2050年,则将超过80亿人。发展中国家人口的增长,要比工业发达国家快得多。在1981—1985年期间,人口的年平均增长率在经济欠发达地区为2.02%,而在较发达地区则为0.64%.据联合国估计,在1986—1990年期 In mid-1987, the population on Earth reached 5 billion. While maintaining its present rate of growth (with an average annual growth rate of 1.7%), by the year 2000, the population on Earth will exceed 6 billion; by 2050, it will exceed 8 billion. The population growth in developing countries is much faster than in industrialized countries. During the period 1981-1985, the annual average rate of increase of the population was 2.02% in the economically underdeveloped area, compared to 0.64% in the more developed areas, and the United Nations estimated that during the period 1986-1990