It would be cool if we could harness the power of trees as they grow in a similar way to that through which we collect solar or wind power, that is, as a tree grows, we find a way to derive power from its lifeforce, not in a way that causes pain or harm to the tree, but in pseudo-symbiotic way that generates power as it grows (or just exists if it reaches the end of its growth cycle). 

I was thinking that covering the tree in some sort of energy absorbing mutually beneficial goo that could transmit its power into a form that could produce electricity for our uses would be workable (we would be working with nature and creating 'envirotechnologies' that would grow and improve as time went on like the ways in which the Ancient Romans used to create docks [so I read a while back {the docks used the power of the sea to become stronger as time passed}]). 

Allowances would definitely have to be made for squirrel and bird activity etc. 

This would definitively ensure the prolonged existence of manifold forests!