巴塞罗那城市上空，西班牙

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城市规划永不停歇

巴塞罗那这熙熙攘攘的城市街道，似乎是纪念世界人口日的一个好地方。越来越多的人口正在涌向城市。据估算，2007年，常居城市人口数首次超过常居农村人口数。如果目前的趋势继续下去，到2050年，世界上大约三分之二的人口将常居于城市。城市规划者和政府官员需要考虑到这一快速增长的趋势。因为供电、供水、公共交通和紧急服务都将因大量人口的涌入而变得捉襟见肘。

联合国在1989年设立了世界人口日，以提高人们对于人口问题的紧迫性和重要性的重视。经过几十万年的发展，世界人口数量终于在1804年左右达到10亿。在此后短短的200多年里，这个数字就超过了77亿。预计2030年世界人口将增长到约85亿，2050年97亿，2100年109亿。多少人口才算是太多了？当世界人口数超过100亿时，我们将面临怎样的生活水平？让自然界繁荣发展的同时，地球能容纳多少人口？这些都是政策制定者在考虑世界的未来时将面对的问题。

Barcelona, Spain

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World Population Day

The bustling city streets of Barcelona seem as good a place as any to mark World Population Day. More and more of us are heading to the city. It’s estimated that 2007 was the first year in which more people lived in cities than in rural areas. If current trends continue, by 2050 about two-thirds of the world population will be living in cities. City planners and government officials will need to account for this rapid increase as power grids, water supplies, public transport and emergency services will all be stretched.

World Population Day was created by the United Nations in 1989 to focus attention on the importance of population issues. After hundreds of thousands of years, the world human population finally reached 1 billion around the year 1804. In just over 200 years since then it has exceeded 7.7 billion. It's expected to grow to around 8.5 billion in 2030, 9.7 billion in 2050, and 10.9 billion in 2100. How many is too many? What standard of living can we expect for people when the population exceeds 10 billion? And how many people can the planet sustain while also allowing nature to thrive? These are among the questions policy makers will confront as they consider the future of our world.