Figs are so popular, that as many as 44 different kinds of bird and monkey have been seen working a shift system on a single tree. 无花果树非常受欢迎 甚至可以吸引多达44种的不同鸟类猴类来交替进食
they're worth tolerating because they provide a valuable early warning system. 它们还是值得忍受的 它们可以在危险来临之前给鼠兔预先的警告
After a rainstorm the saguaro's long shallow root system sucks up the water 暴风雨过后 弁庆柱 用又长又浅的根系吸收水分
that an early warning system is essential. 所以即时预警设备是最重要的
And the Belizean white crab is another creature that is unique to just one cave system. 而伯利兹白蟹是另一个 洞穴生态系统中的特有物种
the greater the chance of damaging some vital life-support system. 便越有可能损坏一些重要的生存设备
On its way the system drains a third of South America. 全部流域面积达到南美洲的1/3
This river has cut the world's longest canyon system - 这条河冲蚀出了世界上最长的峡谷系
An early warning system puts everyone on the alert. “即时预警系统”使大家都警觉起来