U.S. Water News Online
LUXEMBURG, Austria -- The world's population, which has quadrupled over the past 80 years, may never double again, according to new population forecasts by the Population, Development and Environment Project at the International Institute for Applied Systems Analysis (IIASA).
IIASA is a non-governmental research institution sponsored by a consortium of National Member Organizations in 17 nations. The Institute's research focuses on sustainability and the human dimensions of global change.
According to IIASA's projections, there is a 66 percent chance that the world's population will not reach 11.5 billion -- double today's population -- within the next century, if ever. The projections reflect the impact of alternative assumptions for birth rates, migration, and death rates. Based on expert opinions, the projections include confidence levels for global populations and go up to the year 2100.
The projections, and the assumptions on which they are based, are discussed in the new revised edition of The Future Population of the World: What Can We Assume Today? edited by Wolfgang Lutz of the Population, Development and Environment Project at IIASA and published by Earthscan.
"The biggest factor affecting population growth is the continuing decline of fertility in most world regions," said Project leader Wolfgang Lutz. Lutz said that, as a whole, the world's population will probably increase from today's 5.8 billion to around 7.9 billion in 2020, 9.9 billion in 2050, and 10.4 billion by 2100, according to the Project's forecasts.
However, said Lutz, four world regions -- Pacific OECD countries, Eastern Europe, Western Europe, and the European part of the former Soviet Union -- are projected to experience population declines before 2050.
Population in the European part of the former Soviet Union, for example, could decrease due to below-replacement fertility, and relatively high mortality rates. By 2020, the population could fall from its current 238 million to 224 million. By 2050, the population may even fall to 187 million, and could fall to as low as 147 million by 2100.
In contrast, countries in North Africa and the Middle East are likely to experience dramatic population growth. According to IIASA projections, the population in these regions could double and possibly triple over the next 50 years due to current young age structures and high fertility levels.
North Africa's 1995 population level of 162 million is likely to increase to 228 million by 2010 and to 439 million by 2050. The Middle East's 1995 population of 151 million is likely to grow to 234 million by 2010 and to 517 million by 2050, according to IIASA.
Projections for North America reflect a slow but steady increase, climbing from 297 million in 1995 to 356 million in 2020, 405 million in 2050, and to 482 million in 2100. The continued growth of the U.S. population is largely fueled by the assumption of continued migration.
IIASA estimates that there is a 95 percent chance that the population of North America will grow to between 320 million and 400 million by 2020. Toward the end of the next century, population may shrink only if migration is greatly restricted and if the U.S. has a long period of below-replacement fertility.
Lower birth rates affect not only the total population size, but also age distribution, resulting in a steady shift from a current, predominantly young population, to an increasing proportion in the "over 60" age bracket, even in developing countries, according to IIASA. The proportion of those above age 60, IIASA predicts, will expand nearly three-fold, from a current 9.5 percent to 19.7 percent by 2050 and 26.8 percent by 2100.
"This is going to have significant impacts on societies and cause serious problems with pension systems throughout the world," said Lutz.
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