Send them a message or give them a pop-up stating that they need to make a post before they can start a new topic. Something along the lines of
"Welcome to
www.islanddefense.org! If you wish to start a new topic, you are required to make one post beforehand. This is to stop spambots from flooding the forum. Thank you in advance and enjoy your stay!
-Administration
P.S. ignore the flaming, it's the norm around here."
The last part is a joke, but something like this would help new players instead of them going into topics and going "I can't start new topics topics can somebody help please?"
P.S. is it one or five? I forget if it was changed.
