投稿者 nature 日時 2001 年 8 月 02 日 10:28:13:
回答先: 世界の人口は２０７０年にピーク、９０億人に 新推計 投稿者 asahi 日時 2001 年 8 月 02 日 10:25:40:
The end of world population growth
Probably the most pressing concern of the modern world ? both
environmentally and socially ? is the burgeoning global population. The
geometrical growth in numbers over the last century, when extrapolated,
presents a foreboding picture of massive, unsustainable growth and
accompanying famines and heath crises. Yet to simply follow the current
trend is naive, and informed estimates of population trends are
increasingly predicting a less disastrous future.
The latest study, presented by Lutz et al. in this issue, reckons an 85%
chance that global population will peak before 2100, and predicts with
60% certainty that this peak will be less than 10 billion, compared with a
population of 6 billion today. They even give an outside chance, 15%, that
there will be fewer people living at the end of the century than are alive
now.
Their results are notable not just for the relatively low figures projected,
but also for the rigorous probabilistic analysis that accompanies them.
Whereas the United Nation estimates present just four possible outcomes
(constant, high, medium and low), the figures presented by Lutz et al.
include specific chances of a particular scenario occurring on a specific
date. This graphically illustrates the confidence (or otherwise) of
predictions further into the future.
To arrive at their conclusions, the team combined two forecasting
techniques ? 'time series extrapolation', a statistical analysis based on
known figures, and 'expert judgement', whereby key parameters are
estimated taking into account foreseeable events such as disease, war and
fertility trends.
Apart from the lower total population figure estimated (8.8 billion by
2050, compared to 9.3 for the UN's medium estimate, 2000 revision), Lutz
et al. analysis reveal some interesting trends. Population decline in
developed nations is expected to accelerate, with the European part of the
former USSR expected to lose 20% of it population by 2050. Such declines
lead inevitably to ageing populations, and half of all people living in Japan
at the end of the century are predicted to be over 60 years old.
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