+1 on the stabilized woods. They give the best of both worlds. I would not worry much about the trees except in possible extreme cases because so very little wood is used for knife handles. One tree will make hundreds, even thousands, of knife handles. Such woods as walnut, cherry, and olive are routinely harvested from commercial orchards as the trees are replaced near the end of their crop bearing lives.
I've nothing against the synthetics, either. For pure durability and utility, they can be hard to beat, but there are so many synthetics and they are so variable, each must be evailuated on its own.