Cork Bark is used in many terrariums and bio-active setups due to its high resistance to water & the affects of decomposition.  It's a 100% organic and environmentally sustainable item with a low impact on the environment.  Cork bark is harvested from Cork Oak trees every 7 years. Harvesting of the bark causes no harm to the health or growth of the tree itself.  Cork tubes are taken from trees that have already died and rotted over time creating a soft inner layer that is easily removable while cork flat pieces are peeled off the tree one strip at a time.  Cork tubes are comparatively more expensive because the tree must already have rotted on the inside for a considerable amount of time before being able to slide off the tubes.  All our cork bark is heat treated for the safety of enclosures and inhabitants.