From the World Heritage inscription:
In a region that has been subjected to severe glaciation, these parks and reserves, with their steep gorges, covering an area of over 1 million ha, constitute one of the last expanses of temperate rainforest in the world. Remains found in limestone caves attest to the human occupation of the area for more than 20,000 years.
Despite the popularity of Australia as a tourist destination, many people never get to Tasmania, which might be the most unspoiled and beautiful place in the entire country. You can find some of the largest trees in the world (giant eucalyptus) and most unique animals on Earth (Tasmanian Devil).
From an eco tourism standpoint, Tasmania might be the best place to visit in all of Australia.