The world's population could swell¹ to 10.9 billion by the end of the century, a new United Nations analysis found, raising concerns that adding more than 3 billion people to the planet could further deplete² natural resources and accelerate global warming.

联合国最新分析发现，到本世纪末，世界人口可能会增至109亿。人们担心，地球上增加30多亿人口可能会进一步耗尽自然资源，加速全球变暖。

The increase, up from the current count of 7.7 billion people, is expected despite a continued decline in the global fertility rate, which has fallen from 3.2 births per woman in 1990 to 2.5 births per woman this year. Experts say the global fertility rate will continue to decline, but the world’s overall population will still rise, hitting 9.7 billion by 2050.

尽管全球生育率持续下降，但预计届时这一数字仍将远超目前的77亿人口。全球生育率从1990年的3.2下降到今年的2.5。专家表示，全球生育率将继续下降，但世界总人口仍将增长，到2050年达到97亿。

The new report predicts slower population growth than the UN's last assessment³, released in 2017. That estimate projected that the world population would reach a staggering 11.2 billion by the end of the century. The revised figures reflect the downward trend in the globalfertility rate, which means the populations of more countries are shrinking.

这份新报告预测的全球人口增长速度低于联合国2017年发布的上一次评估。此前的评估预计，到本世纪末世界人口将达到惊人的112亿。修正后的数据反映出全球生育率下降的趋势，这意味着更多国家的人口正在减少。

The fastest growth, according to the new report, is most likely to occur in sub-Saharan Africa, which is expected to double its population in the next 30 years. The report also projected that India would become the world's most populous⁴ country by about 2027, surpassing China. Over the next 30 years, 54 other countries are expected to see population declines, including Lithuania, Bulgaria, Ukraine and Japan.

根据这份新报告，人口增长最快的地区最有可能出现在撒哈拉以南非洲，预计在未来30年，该地区的人口将增加一倍。报告还预测，到2027年，印度将超过中国，成为世界上人口最多的国家。在未来30年，预计其他54个国家的人口将出现下降，包括立陶宛、保加利亚、乌克兰和日本。

The United States is estimated to grow from 329 million people in 2019 to 434 million people by the end of the century, with most of that projected increase owing to migration⁵.

据估计，到本世纪末，美国人口将从2019年的3.29亿增长到4.34亿，增加的大部分人口将来自移民。

According to the UN, many of the fastest-growing regions are among the poorest, which could exacerbate⁶ issues of hunger and displacement⁷.

根据联合国的数据，许多人口增长最快的地区都属于最贫穷的地区，这可能会加剧饥饿和流离失所的问题。

Scientists are also concerned about the effect of population growth on climate change. As the global population increases, so will humanity's footprint on the planet.

科学家们还担心人口增长对气候变化的影响。随着全球人口的增长，人类将影响地球上更广泛的区域。

"Our impact on the climate is tied up with population in lots of different ways — what resources people are using, how much industrial production is going on, how much energy is needed for heating, cooling and transportation," Amy Snover, director of the University of Washington's Climate Impacts Group, said. "All of these things affect greenhouse gas emissions⁸, so the more people we have and the more resources we use, the harder it will be to cope with the risks and impacts of climate change."华盛顿大学气候影响小组主任艾米·斯诺弗说：“我们对气候的影响在很多方面都与人口息息相关。人们使用了什么资源，在进行多少工业生产，需要多少能源用于取暖、制冷和运输。所有这些都影响到温室气体的排放，所以人口越多，使用的资源越多，就越难以应对气候变化的风险和影响。”

But population growth is just one of the factors driving climate change. Consumption habits also matter, and they're far from uniform across countries.

但人口增长只是推动气候变化的因素之一。消费习惯也很重要，各国民众的消费习惯也不尽相同。

"There's a massive disconnect between where the most population growth is happening and where the greatest consumption is happening," said Corey Bradshaw, director of the Global Ecology Laboratory at Flinders University in Australia. In other words, the average person's lifestyle in the US is more detrimental⁹ to the environment than the average person's in sub-Saharan Africa. That means rapid population growth in Africa won't be as damaging to the environment as a similar population increase would be in the US.

澳大利亚弗林德斯大学全球生态实验室主任科里·布拉德肖说：“人口增长最快的地方和消费最多的地方之间存在着巨大的脱节。”换句话说，美国普通人的生活方式比撒哈拉以南非洲普通人的生活方式对环境的危害更大。这意味着非洲人口的快速增长对环境的破坏不会像美国人口增长带来的影响那样严重。

In some regions, the increasing population means more people will be vulnerable to rising seas, extreme weather and the spread of infectious diseases, which can all be intensified¹⁰ by climate change.

在一些地区，人口增长意味着更多的人将容易受到海平面上升、极端天气和传染病传播的影响，而这些都可能因气候变化而加剧。

"People in the least-developed countries already tend to be at higher risk of climate change, so depending on how population growth unfolds across the globe, there's going to be more people in hazardous¹¹ areas," Snover said.

斯诺弗说：“最不发达国家的人民已经面临着更高的气候变化风险，因此，将有越来越多的人生活在危险地区，这取决于全球人口增长的趋势。”

She added that one of her biggest concerns is whether the planet will have enough resources to meet people's basic needs. Population growth, combined with climate change, could strain agriculture and access to clean drinking water even more.

她补充说，一个最大的担忧是地球上是否有足够的资源来满足人们的基本需求。人口增长加之气候变化可能会给农业生产和获取清洁饮用水带来更多困难。

"These are all big things," Snover said. "We don't have the luxury of picking only one problem to focus on because they're all coming and they're all coming together."斯诺弗说：“这些都很重要。我们不能只关注一个问题，因为这些问题都出现了，而且是一起出现。”

Scientists say it's difficult to know whether there's a limit to the number of people the planet can sustain — or when we could be approaching it. Still, according to Bradshaw, the 7.7 billion people who inhabit Earth now may already be pushing the planet to a breaking point.

科学家表示，很难知道地球能承受的人口上限，或者何时会接近上限。不过，据布拉德肖说，现在居住在地球上的77亿人可能已经把地球推向了崩溃的边缘。

"Even if we maintained the current status quo and not a single other carbon molecule¹² was released because of human activity," he said, "we'd still see the effects of climate change for at least 300 years from just the emissions that are already in the system."他说：“即使我们维持目前的现状，不再因为人类活动而有更多的碳排放，但由于生态系统中已经存在的碳排放，在未来300年内，我们仍然可以看到气候变化的影响。”