While you can't stop this type of PVP it definitely needs to be slowed down. To completely destroy logs should take a while that's why we have mills in real life - it ain't easy to reduce even a small piece of firewood to sawdust (especially without electricity). Stumps (as mentioned above) should be a royal pain in the butt to destroy - for that matter same with boulders.

Hopefully when agriculture comes in the ability to plant trees also comes in. Though was reading the other day about garden terrorists (in real life) who go around and stealth plant empty lots in big cities. So if you can cut down trees anywhere should you be able to plant trees anywhere?