Forestation History

We were asked:

Certain histories state that Hong Kong lost most of its trees due to widespread cutting around WWII, and that all the current trees/flora that cover the mountains on the island came about as a result of reforestation efforts which started in the 1950s.  However, in many old photos of HK which pre-date WWII, including this one, it appears that there were no trees whatsoever on the hills.

What are the facts behind the history of forest development in Hong Kong?  Was it indeed a barren rock up until the 50s?  Is the heavy jungle now present completely due to human effort?

And Moddsey replied:

There's some information in the comments here:
http://gwulo.com/node/472