Especially, the growth rate in the developing countries, that account for 79% of the world population, is still 1.65% per annum. Some extremists say that even today's level of world population is no longer "sustainable" (1) in view of global environment including resources, energies, and food supplies, and that the Earth may face a catastrophe depending on how far the world population continues to expand.
According to the latest United Nations Population Projections (medium variant of the 1996 version)(2), the world population is estimated to reach 8 billion in 2025, 9.4 billion in 2050, 10.4 billion in 2100, and 10.8 billion in 2150 (See Table 1). The Club of Rome's second report forecast that the population would become stable at the level of 7.7 billion if the world birth rate reached the replacement level in 1990, and that the next century at least will see no catastrophe(3). The world population based on the UN's medium variant, however, is observed to grow at a pace which exceeds The Club of Rome's "sustainable" level in about 2020.
Although the populations of developed countries are not expected to experience major changes, those of developing countries will likely grow further by 3.69 billion to 8.2 billion by 2050(4). The absolute value of the population increase in Asia is relatively great; it is expected to rise by 2.0 billion, from 3.44 billion in 1995 to 5.44 billion in 2050. In particular, the populations of China and India, the world's most populous nations, will increase between 1995 and 2050, from 1.22 billion to 1.52 billion, and from 0.93 billion 1.53 billion respectively. Meanwhile, the relative population growth is the greatest in Africa, where the population will increase by 180%, from 0.72 billion to 2.05 billion during the same period, and will account for 21.8% of world population in 2050.
(2) Optimism about World Population
While the world population is expected to continue to grow substantially in the 21st century, the UN's biennial estimates in the 1990s have revised downwards their figures for the world population in 2025 and 2050 each time; from 8.50 billion and 10.02 billion (estimated in '92), to 8.28 billion and 95.8 billion (estimated in '94), to 8.04 billion and 9.37 billion (estimated in '96)(5). It transpires that population growth and fertility (the major determinant of the former) in the developing countries have declined more than expected every year.
