Their migration may have been set in motion by an increase in population caused by a movement of peoples fleeing the desiccation, or drying up, of the Sahara.
The most successful groups of land plants are those that evolved methods of fertilized sex cell dispersal that are independent of water and structures that protest developing embryos from drying out.
During the tunnel digging, crevice water seeped into the tunnel and resulted in the dry-up of the springs, thus affecting the ecological environment of the mountain region.