In parts of the USA they protect the old covered timber bridges. I believe old timber train trestle also get protected in some states.
Maybe you should launch a Go Fund Me campaign to raise money to buy the old bridge. Alternatively there are timber recyclers who would love to get their hands on those old beams, and supports, as they can be repurposed in many ways. If old piers and jetty timbers can be turned into nice floor boards, I can't see why there would not be a market for the old bridge timbers.
BTW there does seem to be other locals who want to preserve the longest timber bridge in the Southern Hemisphere:
https://www.abc.net.au/news/2015-12-...roject/6996888
There is a nice old one lane bridge just west of Gloucester, I hope they spare that one.