Anyone wanting to see how linksland develops over time should stand on the east side of the 16th green at Royal Dornoch and look down to see how much the beach below has moved left and how much new linksland has been created. The change has been very noticeable even in the 15 years I have been visiting Dornoch.
My guess is much of the sand that has washed into the Dornoch Firth and on to the beach there has been washed down from up by Golspie. The coastline there has been eroding for well over 100 years.
What is interesting (and relevant to this thread) is that you can see how the vegetation has changed in the land as the beach moves further away. What was once beach is now covered is grasses. There are now trees growing in the dune ridge that once separated the beach from the caravan park. That beach is now at least 100 yards further away from the caravan park than it used to be.
My guess is the trees now growing there have not been planted. They are likely growing from seeds dropped by birds. Soils and the vegetation that grows on them do change over time.