Treehugger.com reminds us that wood is perhaps the greenest building material; it is a renewable resource that absorbs carbon dioxide as it grows, which is sequestered in the wood when it is cut into building materials. But until recently its use was limited to low rise structures due to concern about the fire hazard.
It has been known for centuries that heavy timber actually performs better in fire than structural steel; a layer of insulating and fireproof char forms on the outside of it when it burns, protecting the structural integrity of the wood. (It is designed bigger than it needs to be to allow for this char layer.) The recent development of cross-laminated timber creates a building material with all of the virtues of heavy timber without the need for the big trees.