This map from the Wikipedia article on Banksias shows
the distribution of Banksias in Australia. Note that Banksias grow
only in the zones of effective rainfall where there are consecutive
months of effective rainfall forming a growing season (i.e. low
enough monthly variability). Of concern for Ku-ring-gai Banksias
is the movement south into NSW of the zone without Banksias shown
in central and southern Queensland initially leaving only a very
coastal fringe where rainfall bearing clouds just graze the very
coastal areas (such as Northern Beaches) and later very little in
the way of Banksia-containing habitat. As a long term regular bushwalker
I have noticed the gradual thinning out of Banksias from areas where
they were thick so anecdotally it appears that change in underway.
This is confirmed by my recent documentation of Banksia Death (see
menu link of that title).
following series of distribution maps from the Atlas of Living Australia
(ALA) shows the close association of nectar-feeding non-airborne
marsupials and Banksias in their distribution. This makes it unlikely
that these fauna can survive without Banksias being present in their
Pygmy Possums (Cercartetus spp.):
you can see from the above 3 distribution maps that these 3 marsupial
fauna distributions cover the range of Banksias in Australia.