If you're all depressed from reading about death and mortality in Gray's "Elegy Written in a Country Churchyard," not to worry. There are plenty of natural images to counteract all of that doom and gloom. For Gray, the natural world seemed to have provided a source of hope and renewal. All of the natural stuff, after all, goes through cycles of death and decay and new life. Maybe he was hoping that human life would do the same?
Yay, nature! For Gray, nature and natural images represent cycles of death and renewal that provide a source of hope in the face of the inevitability of death and decay.
The speaker evokes images of primitive, primeval nature to make the villagers seem more in touch with the cycles of life and death than typical city-dwellers. What do those guys know, anyway?