Growing timber removes carbon dioxide from the atmosphere, which is inherently a good thing to reduce occurrence of this greenhouse gas. In this way the embodied energy in a timber building can be a much smaller than that of a concrete/masonry building.
However destroying fauna habitat by using rainforrest timbers is clearly not an environmentally conscious decision.
Guidelines to assist sustainable timber specifying:
Source timber from the excellent Mullum Creek development Building Green timber guides
Source timber from CERES Fairwood
Avoid use of unsustainable rainforest timbers i.e. avoid Oregon, Western Red Cedar, Meranti, Merbau, Teak or Luan.
Avoid Merbau or Meranti which are commonly used for decking or screens. Decking or screens should be a wood-plastic composite product or recycled plastic product (see decking page).
All framing timber should be from accredited plantations - either FSC or PEFC/AFS. This is easy to do, at no extra cost, but should be specified.
Decoarative hardwoods can be sourced from the Living Futures Declare label certified Hydrowood – hardwoods recovered from Lake Pieman in Tasmania.
Consider Accoya Wood which is New Zealand Radiate Pine structurally altered for better outdoor performance for cladding, decking and landscaping. It has very good sustainability credentials with drawbacks that it is shipped to the Netherlands for the wood protective process which will build up its embodied energy, and it is quite expensive. As an alternative to cypress pine for sleepers it is twice the price, although a more stable product.