Creation of natural forest: oxymoron or reality?

If a forest of indigenous trees is created from scratch by humans (as to opposed to enrichment planting in an existing forest), can it ever be or become a ‘natural forest’? How many years does it take to reach a state that can be described as restored rather than under restoration?

We give an example of a created African sub-mountainous forest of indigenous trees which has replaced an exotic plantation forest. We are in year 18 of a 30 year project. We are suggesting that provided the landscape includes high native plant diversity, control of exotic and invasive species and demonstration of restoration of trophic levels, a completely planted forest can be restored and in time will be indistinguishable from a natural indigenous forest.