What is the earth compared to in All Quiet on the Western Front?

In Chapter 4 of All Quiet on the Western Front, Paul describes the nature of the earth.  He says that the earth provides the soldiers with shelter and a place of safety.  He comments on the shell holes that get blown into the earth that later serve as places of protection when the men are on the battlefield.  Similarly, Paul describes the trenches that the soldiers prepare to provide safety during combat.  Thus, Paul compares the earth to elements of safety and protection with which he is familiar.  As evidenced in other parts of the novel, Paul has deep respect for the earth and nature in general, and here he explores this by citing its benefits to the soldier during war.