More than a third of NSW's national park land has been burnt by this season's "unprecedented" bushfires, potentially pushing dozens of threatened species including the long-footed potoroo to extinction in the wild.

The Berejiklian government's first assessment of the fires' impact on the state's wildlife, obtained by the Sun-Herald, also reveals about 80 per cent of the Blue Mountains World Heritage Area has been affected and more than half the Gondwana Rainforests.

Bushfires have destroyed about 97 per cent of the known habitat of the endangered long-footed potoroo in NSW, raising fears the animal may become extinct in the wild. Credit:Environment NSW

A separate, shorter report shared with staff on Friday and posted online without fanfare, said the bushfires were "unprecedented in their extent and intensity". As of January 10, they had burnt 5.128 million hectares of NSW, including 2.539 million hectares - or 34.5 per cent of the national park estate.

More than half of the state's heathlands were torched, as were 41 per cent of wet sclerophyll forests and - as a measure of the state's acute drought - more than a third of NSW's rainforests. Even saline wetlands burned.