That's because tumble weeds help spread wildfires.

这是因为翻滚的杂草有助于蔓延野火。

But tumble weeds can catch fire and be blown by the wind across natural barriers, start new fires in other areas.

但翻滚的杂草可能会着火，并被风吹过自然屏障，在其他地区引发新的火灾。