Fires burning around New South Wales have razed koala habitats so extensively “we will probably never find the bodies”, an ecologist has told a parliamentary inquiry.

On Monday the NSW upper house inquiry held an urgent hearing into the state’s koala population and habitat after this season’s “unprecedented” bushfires destroyed millions of hectares of forest.

Some 90 fires continue to burn across the state, half of which are uncontained.

Mark Graham, an ecologist with the Nature Conservation Council, told the inquiry that koalas in most instances “really have no capacity to move fast enough to get away” from fast-moving crown fires that spread from treetop to treetop.

“The fires have burned so hot and so fast that there has been significant mortality of animals in the trees, but there is such a big area now that is still on fire and still burning that we will probably never find the bodies,” Graham said.

The crown fires which have torn through broad expanses of NSW north coast forest, a known biodiversity hotspot, were unprecedented.

“We’ve lost such a massive swath of known koala habitat that I think we can say without any doubt there will be ongoing declines in koala populations from this point forward,” Graham said.

Science for Wildlife executive director Dr Kellie Leigh told the hearing there was no resources or planning in place to save koala populations in the Blue Mountains from fires currently threatening the region.

“We’re getting a lot of lessons out of this and it’s just showing how unprepared we are,” Dr Leigh said on Monday.

“There’s no procedures or protocols in place ... even wildlife carers don’t have protocols for when they can go in after fire.”

The Blue Mountains fires have already hit two-thirds of the northern population the organisation has studied and one-third of the Kanangra-Boyd National Park population, Dr Leigh said.

“We’re just helpless at the moment. [With] business as usual we have no way to deal with this, no way to manage it.”

While 20 koalas have been taken into care “hundreds and hundreds” are being lost to fires in the Blue Mountains.

North East Forest Alliance president and ecologist Dailan Pugh said more than 2,000 koalas may have died in the fires with up to one-third of the koala habitat on the north coast lost.

In October the president of the Port Macquarie koala hospital, Sue Ashton, estimated at least 350 koalas would have died in a bushfire in Crestwood, on the state’s mid-north coast, based on a predicted 60% mortality rate.

The chair of the inquiry, Greens MP Cate Faehrmann, said on Sunday the loss of koalas in NSW should be a catalyst for stronger conservation efforts.

“Hearing that we have lost up to a third of koala habitat and more than 2,000 koalas on the north coast is utterly devastating and should be a wake-up call for this government,” she said.