Maps are amazingly detailed descriptions of the land and very useful for navigating in the bush, but they are vulnerable to weather, and poor care. Torn, damaged maps are harder to read and can leave a group in a tricky situation if they are relying on a single map that gets damaged.
Since maps also may have to last a long time, it helps to take care of them. Some bushwalkers choose to use photocopies instead and transcribe routes/passes and notes to the originals at a later stage. Ensuring that there are backup maps in the group is also very sensible as it’s easy to drop a map in water or lose it in thick scrub.
A pencil is recommended for marking routes or passes on a map. Use light lines so they may be erased quickly without smearing and smudging or leaving marks that may cause confusion later. Back home, consider going over the pencil additions again with a harder pencil or ink pen.