Evan, the islands do have quite a bit of reserved land. The local authority, Redland City Council owns quite a lot too. However, most of it is in private hands. Land on the islands is quite cheap - you can buy 1000 square metres for $22k. Waterfront is much more. But no one is buying these days. Fine by me - I have no neighbours and lots of wildlife. The nice harbour is Perulpa Bay a favourite mooring area and crabbing place: Blue-swimmers - delicious.
But... one day it is all going to get discovered because we are quite close to a capital city. Sigh.
P.S. You do hear the lizards crunching snail sometimes.
