Timber

Timber should be the most sustainable material of all.  It takes carbon out of the atmosphere, gives us oxygen, and provides habitat for wildlife.  It is strong, flexible, insulative, and relatively low in energy to grow and fabricate.  And its compostable at end of life!  The only downside of course, is that our forests have been so overharvested in the past, putting severe habitat pressure on other animals and ecosystems, that we now have to be very careful when we choose timber in our homes, that it comes from sustainable sources.

Knowing what is sustainable timber is unfortunately sometimes a difficult thing, as it depends on sources and logging method, and supply, all of which can change over time. 

Here's our rule of thumb when choosing timber, in order of preference from best to worst:

1. Recycled and reclaimed timber.  (Can be beautiful and usually comes with a history which can be a great later talking point.  Sometimes expensive.  Stock not always constant. Check at the timber recycling centres that the timber is actually recycled, as most of the salvage yards do also sell virgin product.)
2. Bamboo. (While not technically a timber, the bamboo shoot can be harvested and re-grows every 7 years or so.  There is now a lot of different board options and veneers available.)
3. FSC Certified timber.  (The Forest Stewardship Council is a 3rd party certifier assessing a triple environmental bottom line approach.  This is usually much better than the timber industries certifying themselves, and it is good to support this iniative.  Hopefully it will become more mainstream.)
4. Plantation timber.  (While chopping down virgin forest for plantations is terrible.  We now have a lot of plantations, particularly in pine, so we may as well use them, as they keep pressure off the remaining forests.)
5. PEFC & AFS timber. (PEFC is an international logging certification run by the logging industries.  AFS is the Australian version of this.  Having this certitication is better than not having one, though it would be nice to have more independence by the certifier for consumer peace of mind, as in FSC certification.)
6. Australian forest timbers (Will probably be covered by AFS certification, and also covered by government regulation.)
7. Overseas forest timbers  (Typically abstain from these unless you can find out reliably where the timber comes from.  Likely also to have more embodied energy because of transport.)

It is worth taking some time to do research on your timber selection, especially on the bigger quantity purchases.  From an environmental point of view, while focussing on climate change and energy use is important, timber choices are directly leading to habitat destruction and ecosystem degradation today.  So it is quite a critical decision.  

For a good place to start your research see Useful Resources for Building Sustainably, 'Product Databases", also see the old Good Wood Guide from Greenpeace (unfortunately no longer being updated by Greenpeace, but a useful source of easy to engage information to get started.)