The most globally important value of the Greater Blue Mountains is the area's representation of ecosystems dominated by eucalypts.
The eucalypt forest communities of the region are the most diverse and intact scleromorphic (hard-leaved) forests in the Earth's temperate zone. They range from the tall open forests of the high tops and deep valleys to open woodlands and mallee shrublands. These forests together with non-eucalypt ecosystems including rainforests, heaths and wetlands protect a significant proportion of Australia's total biodiversity, which is unique and important on a global scale.
The region's diverse ecosystems demonstrate the continuing natural processes that have changed Australia's vegetation over millions of years. The more recent scleromorphic plants live beside important ancient species surviving from wetter Gondwanan times-such as the Wollemi pine.
The Greater Blue Mountains has over 100 different types of eucalypt - more than 13% of the world total and the greatest concentration of eucalypt diversity anywhere. This abundance is partly due to the area's complex landscape and mostly infertile soils which have promoted evolutionary variation.
The area's total plant diversity is also outstanding, representing 10% of Australia's higher plants. The plant communities provide habitat for a wide variety of animals, particularly invertebrates. A very large number of endemic, relict, restricted, rare and threatened species survive here, including 127 rare or threatened plants and 52 rare or threatened animals. Examples are the Wollemi pine, pink flannel flower, Deane's boronia, brush-tailed rock wallaby, regent honeyeater and broad-headed snake.
The size of the Greater Blue Mountains, its mostly wilderness condition and strong protective management are other important World Heritage qualities, because they will help in the vital task of conserving biodiversity into the future.