If my first year chemistry of long ago does not fail me:

The starch method of extraction would not work for gold, it is too inert to be possible.

I believe silver is less reactive than copper so not much hope there either?

For the environmentalists there is hope because sooner or later a custom chemical ( i.e. complex one ) will likely be developed that will make it possible to extract silver in an environmentally safe way. It is a matter of time for silver price to appreciate enough to develop a custom process cost effectively.

Nature has been doing so all the time, we are merely discovering some of the applications of natures chemistry. We are supplanting those natural 'inventions', but in time will largely replace nature. Knowledge of genes is one major step to that end.