As China’s cities grow, they are also sinking.

随着中国城市的发展，它们也在不断下沉。

An estimated 16 percent of the country’s major cities are losing more than 10 millimeters of elevation per year and nearly half are losing more than 3 millimeters per year, according to a new study published in the journal Science.

根据发表在《科学》杂志上的一项新研究，估计该国16%的大城市每年海拔高度下降超过10毫米，近一半城市每年海拔高度下降超过3毫米。

These amounts may seem small, but they accumulate quickly. In 100 years, a quarter of China’s urban coastal land could sit below sea level because of a combination of subsidence and sea level rise, according to the study.

这些数字看起来可能很小，但积累得很快。根据这项研究，在100年内，由于地表下沉和海平面上升的共同作用，中国四分之一的城市沿海土地可能位于海平面以下。

“It’s a national problem,” said Robert Nicholls, a climate scientist and civil engineer at the University of East Anglia who reviewed the paper. Dr. Nicholls added that, to his knowledge, this study is the first to measure subsidence across many urban areas at once using state-of-the-art radar data from satellites.

“这是一个全国性的问题，”审阅该论文的东安格利亚大学气候科学家和土木工程师罗伯特·尼科尔斯说。尼科尔斯还表示，据他所知，这项研究是第一次使用最先进的卫星雷达数据同时测量许多城市地区的下沉情况。

Subsidence in these cities is caused in part by the sheer weight of buildings and infrastructure, the study found. Pumping water from aquifers underneath the cities also plays a role, as do oil drilling and coal mining, all activities that leave empty space underground where soil and rocks can compact or collapse.

研究发现，这些城市的下沉部分是由建筑物和基础设施的巨大重量造成的。从城市地下含水层抽水也起了作用，石油钻探和煤矿开采也是如此，所有这些活动都会在地下留下空间，可能造成土壤和岩石的压实或坍塌。

Beijing is among the places in the country sinking the fastest. So is nearby Tianjin, where last year thousands of residents were evacuated from high-rise apartment buildings after the streets outside suddenly split apart. Within these cities, sinking is uneven. When pieces of land next to each other subside at different rates, whatever is built on top of that land is at risk of damage.

北京是全国下沉速度最快的城市之一。附近的天津也是如此，去年，天津的几条道路突然裂开，导致数千名居民从高层公寓楼中撤离。在这些城市中，下沉是不均匀的。在同一片土地上，如果相邻的地块以不同的速度下沉，这片土地上建造的任何东西都存在受损的风险。

Other countries, including the United States, have similar problems.

包括美国在内的其他国家也有类似的问题。

“Land subsidence is an overlooked problem that almost exists everywhere,” said Manoochehr Shirzaei, a geophysicist at Virginia Tech who has studied subsidence in American coastal cities using similar methods. Dr. Shirzaei also reviewed the new study on Chinese cities by Zurui Ao of South China Normal University, Xiaomei Hu and Shengli Tao of Peking University, and their colleagues.

“地面沉降是一个被忽视的问题，几乎在任何地方都存在，”弗吉尼亚理工大学的地球物理学家马努切赫尔·希尔扎伊说，他用类似的方法研究了美国沿海城市的沉降。希尔扎伊同样审阅了这篇关于中国城市的新论文，它的作者是华南师范大学的敖祖锐、北京大学的胡晓梅和陶胜利，以及他们的同事。

“I believe the majority of the adaptation strategies that we have, and resiliency plans to combat climate change, are inaccurate, just because they did not include land subsidence,” he said. “It hasn’t been studied the way, for example, sea level rise has been studied.”

“我认为，我们现有的大多数适应策略和应对气候变化的韧性计划都是不准确的，因为它们没有包括地面沉降研究，”他说。“它还没有像海平面上升问题那样被研究过。”

The new study was based on satellite radar measurements of how much the ground surface in 82 major cities, accounting for three-quarters of China’s urban population, moved up or down between 2015 and 2022. The researchers compared these measurements to data on potential contributing factors, like the weight of buildings in these cities and changing groundwater levels underneath them.

这项新研究基于卫星雷达，测量了占中国城市人口四分之三的82个主要城市的地表2015年至2022年间的升降幅度。研究人员将这些测量结果与潜在影响因素的数据进行了比较，比如这些城市建筑物的重量和地下水位的变化情况。

The researchers also combined their subsidence measurements with projections of sea level rise to figure out which cities might end up below sea level. One caveat with these findings is that they assumed a constant rate of subsidence over the next 100 years, but these rates can change along with human activity.

研究人员还将沉降测量结果与海平面上升预测相结合，以确定哪些城市最终可能低于海平面。这些发现中需要注意的一点是，他们假设未来100年下沉的速度是恒定的，但这些速度可能会随着人类活动而改变。

About 6 percent of land in China’s coastal cities currently has a relative elevation below sea level. If the global average sea level rises by 0.87 meters, or a little less than 3 feet, by 2120 (the higher of two commonly used scenarios considered by the researchers) that proportion could rise to 26 percent, this study found.

目前，中国沿海城市约6%的土地相对海拔低于海平面。这项研究发现，如果到2120年全球平均海平面上升0.87米（这是研究人员考虑的两种常用情况中数值较高者），这一比例可能会上升到26%。

Being below sea level doesn’t mean a city is automatically doomed. Much of the Netherlands is below sea level and sinking, but the country has been extensively engineered to prevent flooding in places and to accommodate it in others.

低于海平面并不意味着一座城市就会自动灭亡。荷兰的大部分地区都在海平面以下，并且正在下沉，但这个国家已经进行了广泛的工程设计，以防止某些地方发生洪水，并在其他地方蓄洪。

The key to minimizing damage is limiting groundwater extraction, the researchers wrote. Shanghai is already taking this approach and is sinking more slowly than other Chinese cities. In Japan, groundwater management over the years has proved successful at stabilizing subsidence in Tokyo and Osaka.

研究人员写道，减少破坏的关键是限制地下水的开采。上海已经采取了这种做法，而且下沉速度比中国其他城市要慢。在日本，多年来的地下水管理已证明成功地稳定了东京和大阪的沉降。

Some places are even combating subsidence by injecting water into depleted aquifers in a process called managed recharge.

一些地方甚至通过向枯竭的含水层注水来防治沉降，这被称为“管理补给”。

It’s difficult to stop subsidence entirely, Dr. Nicholls said. “You’ve got to live with what’s left.” Mainly, he said, this means adapting to sea level rise in coastal areas; not just the sea level rise caused by climate change, but also the effects of sinking land.

尼科尔斯说，很难完全阻止地表下沉。“你必须适应剩下的情况。”他说，这主要意味着适应沿海地区的海平面上升；这不仅是由于气候变化所导致，还有陆地下沉的影响。