A fragile environment is one that is both easily disturbed and difficult to restore if disturbed. If you drop a wine glass, or squeeze it too hard, or hit it with something, it will likely break. After it is broken, there is little chance you will be able to mend it. The same can be said for fragile environments. Take Iceland for example. When the Norse first settled on Iceland, they encountered dense, old forests. They also encountered a bird called the dodo. Apparently, they didn't like dodos very much, so they hunted the bird to extinction. Soon, the forests started disappearing. Next, the soil, which was very light in Iceland, started to erode into the sea. Without soil, the Norse couldn't grow crops. What they didn't know about the dodo, was that it was the only animal on the island capable of digesting the seeds of trees, thus maintaining the forest. Had they known, they probably would have been much kinder to the dodo. The point is that all it took was the extinction of one species for the whole landscape of Iceland to change. What was once a land of old, green forests is now a largely desolate landscape. That, in essence, is a fragile environment.