500 million humans live in the world's desert lands,

5亿人生活在沙漠地区
More than the combined population of europe.

比欧洲的人口总数还要多
They know the value of water.

他们知道水的价值
They know how to use it sparingly.

他们知道如何节省使用
Here, they depend on wells replenished by fossil water,

这里他们依靠以原生水补充的水井
Which accumulated underground in the days when it rained on these deserts,

这些水是在25000年前沙漠下雨的时候
25,000 years ago.

渗入地下形成的
Fossil water also enables crops to be grown in the desert...

原生水也能让庄稼在沙漠中生长
To provide food for local populations.

为当地人提供粮食
The fields' circular shape...

管子围绕一个中心轴灌溉耕地
Derives from the pipes that irrigate them around a central pivot.

耕地就围绕这些管子形成圆形
But there is a heavy price to pay.

但这要付出沉重代价