About a million hectares burnt in national parks in and around the Hunter Region.

Google Earth mapping, compiled by the government and University of NSW, has revealed the extent of bushfire damage to the canopy in national parks.

The mapping shows the damage caused by mega-fires in Wollemi and Yengo national parks. These fires sent huge amounts of smoke across the Hunter in December and January during westerly winds.

The notorious Wollemi fire, known as the Gospers Mountain blaze, set a record for being the biggest forest fire in Australian history.

A government spokesperson said the Google mapping was created to "detect how badly the tree canopy has burnt by measuring the change in the colour of vegetation before and after a fire".

The mapping was helping decision makers, ecologists and researchers in their "assessments and response efforts to the recent fires".

Additional fire-severity mapping was being done to guide conservation work and "ecological reconstruction".

National Parks Association Hunter branch president Ian Donovan said "extensive areas were burnt in the Yengo and Wollemi national parks".

"There's the potential with these big fires that there'd be local extinctions of species in particular areas," Mr Donovan said.

It could be difficult for some species to "recolonise back into those areas".

"It's hard to predict what the long-term effects are in Wollemi and so on. It's a huge area of complexity. You can't just generalise - it's not just gum trees. There's a lot of variety in the landscape.

"Different types of ecological communities will respond differently."

The government said the fire intensity and severity varied across fire grounds.

"Pockets of unburnt or slightly burnt canopy provide refuges for a number of species during fires.

"Long-term survival is more complex and depends on factors such as access to food, water and habitat recovery, which is affected by fire severity and future weather conditions."

The Google mapping shows how badly the tree canopy was burnt. It does not provide detailed data on the impact of fires on specific species. Map data had been compared with information and records for threatened species, species sightings and other modelling to "inform a preliminary assessment of the impact of the fires on NSW biodiversity".

Further assessments and surveys were being done to "directly assess" impacts on flora and fauna.

The government said it was planning for the long-term restoration and recovery of "native animals, plants and landscapes across NSW".

"This includes protecting the remaining areas of unburnt habitat. The government will continue to update our response as we improve our understanding of the impacts of these unprecedented fires."