Dr Box told the Royal Commission into National Natural Disaster Management on Wednesday the expert panel advising government on bushfire recovery for threatened species had identified more than 750 species in need of urgent intervention.

"Some are those are already listed as threatened but some aren't. I consider there will be a large number of species that will be considered under the EPBC Act but I don't have a number to put on that right now," Dr Box said.

The fires covered an "unusually large area and in many places they burnt with an unusually high intensity", Dr Box said.

About 300 of the 1800 species listed as threatened under the EPBC Act were in the path of the fire and had more than 10 per cent of their known or likely range affected.

"The entire range of some species was burnt," Dr Box said.

"Of the 377 [species] in the path of the fire, 49 threatened species had more than 80 per cent of their known or likely range within the fire extent.

"A further 65 threatened species had more than 50 per cent of their known or likely range in the fire extent and this includes plants and mammals and plants and reptiles and fish and invertebrates."

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Species that were considered at risk before the fires were now at an increased risk of extinction, while others that were considered secure were now considered "imperiled", Dr Box said.

Dr Box said the expert panel had determined 119 animal species, 471 plant species and 191 invertebrate species in need of urgent intervention.

This included a number of species already listed as threatened like the Kangaroo Island Dunnart - which lost 90 per cent of its range - but also species not considered threatened before, including the Albert's Lyrebird and the Yellow-Bellied Glider.

However efforts to determine the scale of the damage have been hampered due to inconsistent mapping between each state and territory.

Emma Campbell of the Department of Water, Environment and Energy said, "it was harder than it should have been to actually get a map of where the fire scar was, because everyone was working on different systems".

Inconsistent data and taxonomy was also not helpful, Ms Campbell said.

However Dr Box said work was underway to improve species observation data and to collaboratively identify critical assets.

ACT officials told the commission they managed to perform a rapid risk assessment of threatened species within five days of the Orroral Valley bushfire After the 2003 fires, that process took several months.

However the Namadgi National Park remains closed more than since months after gates were initially closed because of the damage sustained.