In places, there are a million pieces of plastic per square kilometre.

在某些地方，每平方公里甚至有100万件塑料垃圾。

In one month, dust fall can reach as much as 17kg per square kilometre.

在一个月的时间里，每平方公里差不多要落下17kg的灰尘。

For shooting to go ahead, the density of birds must exceed 200 grouse per square kilometre.

为了狩猎的需要，这种鸟类的每平方千米种群密度必须超过200只。

A landscape with an average of 45 people per square kilometre is ideal for sparking wildfires.

人口密度为45人每平方公里的风景区最容易发生森林火灾。

Yet with around 7, 000 people per square kilometre, Singapore is the third most densely populated country in the world.

然而新加坡是世界上人口最稠密的国家之一，人口密度位居世界第三，每平方公里达7000人之多。