What is the canon of Highland rewilding? (This in response to Ferdinanda and Sarah, who were interested.)
I would start with The Highland Clearances by Prebble, for the social history, and an explanation of why there is depopulated wilderness here at all.
(Add A Dance Called America by Hunter, for deep background.)
Next, A Herd of Red Deer by Fraser Darling, in which the original proposition is hidden in a footnote.
Rhum: The Natural History of an Island by Clutton-Brock and Ball contains the results of the most important other example of an experiment in Highland ecological restoration and species introduction (which experiment is still running), but there are many supporting papers, so a literature review relating to conservation on Rum would be necessary.
A series of tree, bird, and mammal keys would be required.
A few back issues of Reforesting Scotland would be helpful.
That would make a very good start.