As far as I understand, the natural progression to growing forest easily breaks once the forest is gone. Large swaths of land around the Mediterranean are now d

As far as I understand, the natural progression to growing forest easily breaks once the forest is gone. Large swaths of land around the Mediterranean are now desert but used to be forest, until they were cut down. Erosion and other factors than stop new forests from growing. In these cases you need to kickstart the process by sending the correct starter.