To reply to the original question.
You are -never- going to get a 100% cover of trees.
There will be land slips on the hills, ridges that have no or very few
trees on them.
In forestry bush you will have fire breaks and access roads.
Rivers and streams are always there as open areas.

There is the old adage about the most useless things in aviation.
Runway behind you, altitude above you and fuel in the bowser.

When you do a crosscountry -always- look for suitable sites for
emergency landings. it may well save your life one day...