Most of the ostensibly 'eco' furniture makers are using timber from managed woodlands where replanting and harvesting is part of the industry. The 'plant a tree' gimmick is just a gloss on a process that is renewable anyway.
Practically all our furniture is second hand to antique; donated, rescued, inherited or bought at junk shops or at auction. In most cases we are probably at least the second if not the fifth, sixth, or seventh owner. That way our share of the wood used in the furniture is very small indeed and was harvested a hundred years ago or more.
For a wood to be enjoyable it has to be well managed, otherwise it can become an impenetrable mix of brambles, nettles and dead wood.