You only need a small piece of fynbos to start a fire, so if you plan your excavators so that they either just cut off one tree, or that a tree creates fynbos across a river, you can use that little piece as a firestarter for forests while keeping all of the rest of the fynbos for biodiversity.
This way you're not using up the existing trees for forests, and any new trees that you get from the Arboretum can also potentially be used for beehives.