求翻译：People are making more and more demands on the world’s natural resources. If babies born in 1991 live for 80 years, the human population of the world may be anything from twice to three times the present total by 2070. In other words, they will have to share what is left of the earth’s resources with between 10 and 15 billion other people. But hopefully there will be a significant decrease in the growth of population. What if this does not happen? The answer is that by the time before the babies born in 1991 reach the age of 40 they could be sharing resources with as many as 10 billion other people.是什么意思？

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