Good question. Generally speaking timber is a highly sustainable material because it absorbs and locks away carbon and it takes very little energy to manufacture useable sections. As far as what species of timber to use? There is a simple answer and a complex one. The simple approach in a nutshell is to follow my table which ranks the most sustainable to the least sustainable. If your not from australia you can typically substitute the name of another developed country. Unfortunately countries with less wealth tend to have to exploit their forests more ruthlessly.
1) recycled timber ! The best. This is typically pine or Australian hardwood. Both are great. It won't shrink and the old hardwood is fantastic quality timber.
2) F.S.C certified (Australian) timber. F.S.C is the strictest most reliable certification system around.
2) plantation pine. This includes solid pine, cypress pine, treated pine and hoop pine. The advantage of pine is that it is plantation (a farm) so you know 100% that it hasn't come out of an old growth forest.
3) composite timbers . These are products like plywood and composite beams and posts made from small pieces of timber . This means that there is little waste in the production and they don't need to use big trees to create large beams and so on .
4) Australian hardwood. This is most likely harvested from state forests or plantation forests. Ok yes there are different opinions on this but on the whole it's a lot safer than buying unregulated timber from south east Asian ancient forests. There is also the argument that native forests are better for australia than pine forests.
5) F.S.C. Certified (non Australian) timber. This includes timber from all over the world but mainly it's from untapped forests in Asia and Africa. This timber is amazing quality because it comes from old trees out of ancient forests. Do not buy any timber from Asia or Africa that is not F.S.C certified. Do not!! I actually only buy even the F.S.C. Certified timber if no other options are available.
Do not buy
- Merbau (unless fsc) - it is a south east Asian timber with orangutan claw marks on it. You will find that shamefully this is everywhere in hardware stores!! If you want to destroy the last great forests on earth then go ahead and do your deck in merbau or other nice Asian timbers.
- new timber products (plywood etc) made from south east Asian timbers
- timber products like bread boards from china and asia, unless it's bamboo
So there it is. Basically just get recycled timber, pine based products or Australian hardwood products and the world may be half decent when we get old.