Sure they can. They can solicit volunteers to emigrate. They can also take the possibility that the Invasions will one day come to their island seriously and lay the groundwork for their defenses by creating guilds, collecting portal stones, making treaties, etc. Bedwyr was trying to do just that with Manifest Path. From what I have seen, IC no one on the other islands, with the exception of Dwilight, takes the possibility of an Invasion even remotely seriously.
