The world鈥檚 population may reach a peak of nine billion as early as 2070 and then start to shrink, according to a new analysis by Austrian researchers.
Wolfgang Lutz, of the International Institute for Applied Systems Analysis, and his team created thousands of simulations of the future world population and evaluated them, assigning probabilities to each range of possibilities.
They think there is an 85 per cent chance that the global population will stop growing before the end of the century 鈥� most probably by 2070. More than one third of people alive in 2100 will be over 60, they say. In Japan, the figure will be one half.
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Detailed population projections are vital for governments planning long-term economic strategies, says Lutz. However, Nico Keilman, an economist at the University of Oslo, warns that population projections are notoriously unreliable. The 鈥減robabalistic statements are themselves uncertain to some extent鈥�, he writes in the journal Nature.
Declining fertility rates
Lutz thinks declining fertility rates around the world are the main driving force behind the slowing in population growth.
鈥淲e hope these findings will help people get away from the apocalyptic view that the population will explode in the future,鈥� he told New 杏吧原创. 鈥淗umankind can control the future by controlling fertility.鈥�
The population will start to shrink when the average number of children per woman falls below 2.1 (this figure is above two to provide for childhood mortality). 鈥淲e are assuming that fertility levels in most parts of the world will soon go below the replacement level,鈥� Lutz says. 鈥淚n some countries, like India, it will probably go down to 2.1 and then stay constant.鈥�
In some parts of Europe, fertility levels have already dropped dramatically. In Spain, the average number of children per woman is 1.2. In Russia the figure is 1.1.
鈥淚n Eastern Europe and the former Soviet Union, we have already seen the peak of population size, and it will decline in the future,鈥� Lutz says. 鈥淗owever, the US will continue to grow due to immigration.鈥� He adds: 鈥淭his shows the notion that poor countries are growing and rich countries are shrinking is not true.鈥�
Lutz thinks fertility is dropping as more women are able to go for 鈥渜uality鈥� of children, rather than quantity. 鈥淭he reason it鈥檚 dropping below the replacement level in Europe is probably because of fundamental changes to the role of women in society,鈥� he adds.
But mortality from AIDS and other poverty-related illnesses is also a key factor, says Lutz. The possibility of future unpredicted health disasters 鈥� such as another AIDS 鈥� is also included in the team鈥檚 projections.
Considering climate
Several groups are working on population predictions. In September, the United Nations Population Fund will release a new report projecting that the world population will peak at 9.3 billion by 2050.
Lutz says there are several key differences in the way the UNPF has made its predictions, compared with his team鈥檚 approach.
鈥淭he UN does not consider climate change 鈥� which we think will hit agricultural production in Africa and southern Asia in particular,鈥� says Lutz. 鈥淲e are also a lot more pessimistic about African mortality than the UN. In 2020, we assume life expectancy in Africa to be about 10 years lower than the UN.鈥�
While more developed countries will see a 鈥渨indow of opportunity鈥� when a relatively large (though ageing) workforce is available, Africa and southern Asia will continue to struggle, say the team. 鈥淚鈥檓 not optimistic about that part of the world at all,鈥� Lutz says.
Journal reference: Nature (vol 412, p 543)