While the country laments the horrific loss of wildlife due to bushfires, talks are being held on Kangaroo Island to ensure its decimated koala population does not regenerate.

Key points: Kangaroo Island koala population estimated to have been killed by up to 90 per cent

Kangaroo Island koala population estimated to have been killed by up to 90 per cent Koalas on the island were introduced and unsustainable

Koalas on the island were introduced and unsustainable Government to explore keeping depleted population manageable

Koalas are a pest on Kangaroo Island — they were introduced in the 1920s in response to population decline across the country's south-east caused by the fur trade.

Starting with 18 disease-free koalas from French Island in Victoria, the population spiralled out of control to an estimated 50,000 by last year, creating unsustainable pressure on the local environment.

"I'm loath to put a number on how many koalas we have lost as a result of the fires, and no-one wants to see any native species, or any animal, suffer in the fire," SA Environment Minister David Speirs told ABC Radio Adelaide's Mornings.

"But we have certainly lost tens of thousands and could be down to a population of 5,000 to 10,000.

"According to the ecologists I have spoken to, it's likely to be a much more sustainable population on the island."

Koalas thriving in Adelaide

While koalas are a threatened species in many parts of Australia, this is not the case in the Mount Lofty Ranges, the foothills of Adelaide and the southern suburbs, where a "decent, healthy population" of about 150,000 koalas is thriving.

There is no shortage of koalas in the Adelaide foothills. ( ABC Radio Adelaide: Malcolm Sutton )

But those on Kangaroo Island, which were originally introduced to Flinders Chase National Park, have a very limited habitat.

The Government said this resulted in large areas of eucalyptus trees dying due to over-browsing (consuming all the leaves of a tree so it dies).

They also have a preference for the manna gum, which is already rare on Kangaroo Island and provides critical habitats for another native animals.

Many residents subsequently consider koalas to be a pest.

"There was a situation where these koalas were eating themselves out of house and home," Mr Speirs said.

"They were causing significant pressure on vegetation as well, and the environment department for many years had been undertaking a sterilisation program."

Despite some koalas being translocated to the mainland, the population has continued to grow, with culling ruled out.

Fires have devastated koala numbers on Kangaroo Island. ( Supplied: Humane Society )

Gum plantations accelerate population growth

Mr Speirs said tree plantations on the island had given the koalas more food, habitats and safe places to breed, which had accelerated the growth of the population.

"A lot of these koalas were in the plantation forests on the island, which are burnt and are due to be harvested where they can be."

He said in the medium term those trees would no longer be available and it was not yet certain if the private company responsible for them would replant after nearly half of the island was scorched in this summer's bushfires.

"We're going to have a situation on Kangaroo Island where the vegetation for these koalas to live in and graze on has hugely reduced, and I think that will go a long way to controlling the population.

"This is the sort of thing I need to sit down in the coming weeks, once I get a handle on the situation, and work through with the ecologists to work out what will happen with the koala population."